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  • 1.
    Aranke, Omkar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Gupta, Mohit Kumar
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Kjellman, Björn
    GKN Aerospace Sweden AB, Trollhättan, Sweden.
    Microstructural Evolution and Sintering of Suspension Plasma-Sprayed Columnar Thermal Barrier Coatings2019In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, no 1-2, p. 198-211Article in journal (Refereed)
    Abstract [en]

    Suspension plasma spray (SPS) is capable of producing coatings with porous columnar structure, and it is also a much cheaper process compared to the conventionally used electron beam physical vapor deposition (EB-PVD). Although TBCs with a columnar microstructure that are fabricated using SPS have typically lower thermal conductivity than EB-PVD, they are used sparingly in the aerospace industry due to their lower fracture toughness and limited lifetime expectancy. Lifetime of TBCs is highly influenced by the topcoat microstructure. The objective of this work was to study the TBCs produced using axial SPS with different process parameters. Influence of the microstructure on lifetime of the coatings was of particular interest, and it was determined by thermal cyclic fatigue testing. The effect of sintering on microstructure of the coatings exposed to high temperatures was also investigated. Porosity measurements were taken using image analysis technique, and thermal conductivity of the coatings was determined by laser flash analysis. The results show that axial SPS is a promising method of producing TBCs having various microstructures with good lifetime. Changes in microstructure of topcoat due to sintering were seen evidently in porous coatings, whereas dense topcoats showed good resistance against sintering.

  • 2.
    Bahbou, M. Fouzi
    et al.
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Choquet, Isabelle
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Clement, Uta
    Numerical and experimental study of Ni-particle impact on a ti-surfaceIn: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016Article in journal (Refereed)
  • 3.
    Bahbou, M. Fouzi
    et al.
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Nylén, Per
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    On-Line Measurement of Plasma-Sprayed Ni-Particles during Impact on a Ti-Surface: influence of Surface Oxidation2007In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 16, no 4, p. 506-511Article in journal (Refereed)
    Abstract [en]

    The objective of this study was to analyze the impact of plasma-sprayed Ni5%Al particles on polished and grit-blasted Ti6Al4V samples under oxidized and nonoxidized conditions. For this purpose, measurements of thermal radiation and velocity of individual plasma-sprayed particles were carried out. From the thermal radiation at impact, splat diameter during flattening and temperature evolution during cooling were evaluated. Characteristic parameters related to the quality of contact between the splat and the substrate were retrieved. The flattening speed was introduced to characterize wetting, while the cooling rate was used to characterize solidification. The idea was to get a signature of particle impact for a given surface roughness and oxidation state by identifying parameters which strongly affect the splat behavior. Sieved Ni5%Al powder in a narrow range (+65 −75 μm) was sprayed on four sets of titanium alloy surfaces, consisting of polished and grit-blasted samples, one set had a nonoxidized surface and the other one was oxidized in an oven at 600 °C for two hours. Resulting splats after impact were characterized by scanning electron microscopy, the splats on oxidized surface showed pores in their core and detached fingers at the periphery. The cooling rate and flattening degree significantly increased on the oxidized smooth surface compared to the nonoxidized one. This trend was not found in grit-blasted surfaces, which implies that impact phenomena are different on grit-blasted surfaces than on smooth surfaces thus further work is needed.

  • 4.
    Bahbou, M. Fouzi
    et al.
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Nylén, Per
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    On-Line measurement of plasma-sprayed ni-particles during impact on a ti-surface: influence of surface oxidation2007In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 16, no 6, p. 506-511Article in journal (Refereed)
    Abstract [en]

    The objective of this study was to analyze the impact of plasma-sprayed Ni5%Al particles on polished and grit-blasted Ti6Al4V samples under oxidized and nonoxidized conditions. For this purpose, measurements of thermal radiation and velocity of individual plasma-sprayed particles were carried out. From the thermal radiation at impact, splat diameter during flattening and temperature evolution during cooling were evaluated. Characteristic parameters related to the quality of contact between the splat and the substrate were retrieved. The flattening speed was introduced to characterize wetting, while the cooling rate was used to characterize solidification. The idea was to get a signature of particle impact for a given surface roughness and oxidation state by identifying parameters which strongly affect the splat behavior. Sieved Ni5%Al powder in a narrow range (+65 −75 μm) was sprayed on four sets of titanium alloy surfaces, consisting of polished and grit-blasted samples, one set had a nonoxidized surface and the other one was oxidized in an oven at 600 °C for two hours. Resulting splats after impact were characterized by scanning electron microscopy, the splats on oxidized surface showed pores in their core and detached fingers at the periphery. The cooling rate and flattening degree significantly increased on the oxidized smooth surface compared to the nonoxidized one. This trend was not found in grit-blasted surfaces, which implies that impact phenomena are different on grit-blasted surfaces than on smooth surfaces thus further work is needed.

  • 5.
    Bahbou, M. Fouzi
    et al.
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Nylén, Per
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Wigren, J.
    Volvo Aero, Trollhättan.
    Effect of grit blasting and spraying angle on the adhesion strength of a plasma-sprayed coating2004In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 13, no 4, p. 508-514Article in journal (Refereed)
  • 6.
    Choquet, Isabelle
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Johansson, Jimmy
    Volvo Aero Corporation, Trollhättan.
    Wigren, Jan
    Volvo Aero Corporation, Trollhättan.
    Clogging and lump formation during atmospheric plasma spraying with powder injection downstream the plasma gun2007In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 16, no 4, p. 512-523Article in journal (Refereed)
    Abstract [en]

    This study aimed to numerically and experimentally investigate lump formation during atmospheric plasma spraying with powder injection downstream the plasma gun exit. A first set of investigations was focused on the location and orientation of the powder port injector. It turned out impossible to keep the coating quality while avoiding lumps by simply moving the powder injector. A new geometry of the powder port ring holder was designed and optimized to prevent nozzle clogging, and lump formation using a gas screen. This solution was successfully tested for applications with Ni-5wt.%Al and ZrO2-7wt.%Y2O3 powders used in production. The possible secondary effect of plasma jet shrouding by the gas screen, and its consequence on powder particles prior to impact was also studied.

  • 7.
    Curry, Nicholas
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Janikowski, Wysomir
    University of Manchester.
    Pala, Zdenek
    Academy of Sciences of the Czech Republic, Institute of Plasma Physics.
    Vilémová, Monica
    Academy of Sciences of the Czech Republic, Institute of Plasma Physics.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Impact of Impurity Content on the Sintering Resistance and Phase Stability of Dysprosia- and Yttria-Stabilized Zirconia Thermal Barrier Coatings2014In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 23, no 1-2, p. 160-169Article in journal (Refereed)
    Abstract [en]

    Dysprosia-stabilized zirconia (DySZ) is a promising candidate to replace yttria-stabilized zirconia (YSZ) as a thermal barrier coating due to its lower inherent thermal conductivity. It is also suggested in studies that DySZ may show greater stability to high temperature phase changes compared to YSZ, possibly allowing for coatings with extended lifetimes. Separately, the impurity content of YSZ powders has been proven to influence high-temperature sintering behavior. By lowering the impurity oxides within the spray powder, a coating more resistant to sintering can be produced. This study presents both high purity and standard purity dysprosia and YSZ coatings and their performance after a long heat treatment. Coatings were produced using powder with the same morphology and grain size; only the dopant and impurity content were varied. Samples have been heat treated for exposure times up to 400 h at a temperature of 1150 °C. Samples were measured for thermal conductivity to plot the evolution of coating thermal properties with respect to exposure time. Thermal conductivity has been compared to microstructure analysis and porosity measurement to track structural changes. Phase analysis utilizing x-ray diffraction was used to determine differences in phase degradation of the coatings after heat treatment. © 2013 ASM International.

  • 8.
    Curry, Nicholas
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Li, Xin-Hai
    Siemens Turbomachinery.
    Tricoire, Aurelien
    Volvo Aero Corp.
    Dorfman, Mitch
    Sulzer Metco.
    Next Generation Thermal Barrier Coatings for the Gas Turbine Industry2010In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, ISSN 1059-9630, Vol. 20, no 1-2, p. 108-115Article in journal (Refereed)
    Abstract [en]

    The aim of this study is to develop the next generation of production ready air plasma sprayed thermalbarrier coating with a low conductivity and long lifetime. A number of coating architectures wereproduced using commercially available plasma spray guns. Modifications were made to powder chemistry,including high purity powders, dysprosia stabilized zirconia powders, and powders containingporosity formers. Agglomerated & sintered and homogenized oven spheroidized powder morphologieswere used to attain beneficial microstructures. Dual layer coatings were produced using the two powders.Laser flash technique was used to evaluate the thermal conductivity of the coating systems from roomtemperature to 1200 C. Tests were performed on as-sprayed samples and samples were heat treated for100 h at 1150 C. Thermal conductivity results were correlated to the coating microstructure using imageanalysis of porosity and cracks. The results show the influence of beneficial porosity on reducing thethermal conductivity of the produced coatings.

  • 9.
    Curry, Nicholas
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Östergren, Lars
    Volvo Aero Corporation, Trollhättan.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery, Finspång.
    Dorfman, Mitch
    Sulzer Metco, Westbury, USA.
    Evaluation of the Lifetime and Thermal Conductivity of Dysprosia-Stabilized Thermal Barrier Coating Systems2013In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 22, no 6, p. 864-872Article in journal (Refereed)
    Abstract [en]

    The aim of this study was the further development of dysprosia stabilised zirconia coatings for gas turbine applications. The target for these coatings was a longer lifetime and higher insulating performance compared to today's industrial stan dard thermal barrier coating. Two morphologies of ceramic top coat were studied; one using a dual layer systems and the second using a polymer to generate porosity. Evaluations were carried out using laser flash technique to measure thermal properties. Lifetime testing was conducted using thermal shock testing and thermo-cyclic fatigue testing. Microstructure was assessed with SEM and Image analysis used to characterise porosity content. The results show that coatings with an engineered microstructure give performance twice that of the present reference coating.

  • 10.
    Ekberg, Johanna
    et al.
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Ganvir, Ashish
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Klement, Uta
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Creci, Simone
    Chalmers University of Technology, Department of Chemistry and Chemical Engineering, Gothenburg, Sweden.
    Nordstierna, Lars
    Chalmers University of Technology, Department of Chemistry and Chemical Engineering, Gothenburg, Sweden.
    The Influence of Heat Treatments on the Porosity of Suspension Plasma-Sprayed Yttria-Stabilized Zirconia Coatings2018In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 27, no 3, p. 391-401Article in journal (Refereed)
    Abstract [en]

    Suspension plasma-sprayed coatings are produced using fine-grained feedstock. This allows to control the porosity and to achieve low thermal conductivity which makes the coatings attractive as topcoats in thermal barrier coatings (TBCs). Used in gas turbine applications, TBCs are exposed to high temperature exhaust gases which lead to microstructure alterations. In order to obtain coatings with optimized thermomechanical properties, microstructure alterations like closing of pores and opening of cracks have to be taken into account. Hence, in this study, TBC topcoats consisting of 4 mol.% yttria-stabilized zirconia were heat-treated in air at 1150 °C and thereafter the coating porosity was investigated using image analysis (IA) and nuclear magnetic resonance (NMR) cryoporometry. Both IA and NMR cryoporometry showed that the porosity changed as a result of the heat treatment for all investigated coatings. In fact, both techniques showed that the fine porosity decreased as a result of the heat treatment, while IA also showed an increase in the coarse porosity. When studying the coatings using scanning electron microscopy, it was noticed that finer pores and cracks disappeared and larger pores grew slightly and achieved a more distinct shape as the material seemed to become more compact.

  • 11.
    Eriksson, Robert
    et al.
    Siemens Industrial Turbomachinery AB, Berlin, Germany.
    Gupta, Mohit
    University West, Trollhättan, Sweden.
    Broitman, Esteban
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Jonnalagadda, Krisha Praveen
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Nylén, Per
    University West, Trollhättan, Sweden.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Stresses and Cracking During Chromia-Spinel- NiO Cluster Formation in TBC Systems2015In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 24, no 6, p. 1002-1014Article in journal (Refereed)
    Abstract [en]

    Thermal barrier coatings (TBC) are used in gas turbines to reduce the temperatures in the underlying substrate. There are several mechanisms that may cause the TBC to fail; one of them is cracking in the coating interface due to extensive oxidation. In the present study, the role of so called chromia-spinel-NiO (CSN) clusters in TBC failure was studied. Such clusters have previously been found to be prone to cracking. Finite element modeling was performed on a CSN cluster to find out at which stage of its formation it cracks and what the driving mechanisms of cracking are. The geometry of a cluster was obtained from micrographs and modeled as close as possible. Nanoindentation was performed on the cluster to get the correct Young’s moduli. The volumetric expansion associated with the formation of NiO was also included. It was found that the cracking of the CSN clusters is likely to occur during its last stage of formation as the last Ni-rich core oxidizes. Furthermore, it was shown that the volumetric expansion associated with the oxidation only plays a minor role and that the main reason for cracking is the high coefficient of thermal expansion of NiO.

  • 12.
    Eriksson, Robert
    et al.
    Siemens AG, Large Gas Turbines, Huttenstr. 12, 10553, Berlin, Germany.
    Gupta, Mohit Kumar
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Broitman, Esteban
    Linköping University. IFM, 58183, Linköping, Sweden.
    Jonnalagadda, Krishna Praveen
    Linköping University, IEI, 58183, Linköping, Sweden.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Lin Peng, Ru
    Linköping University, IEI, 58183, Linköping, Sweden.
    Stresses and Cracking During Chromia-Spinel-NiO Cluster Formation in TBC Systems2015In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 24, no 6, p. 1002-1014Article in journal (Refereed)
    Abstract [en]

    Thermal barrier coatings (TBC) are used in gas turbines to reduce the temperatures in the underlying substrate. There are several mechanisms that may cause the TBC to fail; one of them is cracking in the coating interface due to extensive oxidation. In the present study, the role of so called chromia-spinel-NiO (CSN) clusters in TBC failure was studied. Such clusters have previously been found to be prone to cracking. Finite element modeling was performed on a CSN cluster to find out at which stage of its formation it cracks and what the driving mechanisms of cracking are. The geometry of a cluster was obtained from micrographs and modeled as close as possible. Nanoindentation was performed on the cluster to get the correct Young’s moduli. The volumetric expansion associated with the formation of NiO was also included. It was found that the cracking of the CSN clusters is likely to occur during its last stage of formation as the last Ni-rich core oxidizes. Furthermore, it was shown that the volumetric expansion associated with the oxidation only plays a minor role and that the main reason for cracking is the high coefficient of thermal expansion of NiO. © 2015 ASM International

  • 13. Eriksson, Robert
    et al.
    Gupta, Mohit Kumar
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Broitman, Esteban
    Linköping University.
    Jonnalagadda, Krishna Praveen
    Linköping University.
    Nylén, Per
    University West, Department of Engineering Science, Research Environment Production Technology West.
    Peng, Ru Lin
    Linköping University.
    Stress and Cracking during Chromia-Spinel-NiO Cluster Formation in Thermal Barrier Coating Systems2015In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 24, no 6, p. 1002-1014Article in journal (Refereed)
    Abstract [en]

    Thermal barrier coatings (TBC) are used in gas turbines to reduce the temperatures in the underlying substrate. There are several mechanisms that may cause the TBC to fail; one of them is cracking in the coating interface due to extensive oxidation. In the present study, the role of so called chromia-spinel-NiO (CSN) clusters in TBC failure was studied. Such clusters have previously been found to be prone to cracking. Finite element modeling was performed on a CSN cluster to find out at which stage of its formation it cracks and what the driving mechanisms of cracking are. The geometry of a cluster was obtained from micrographs and modeled as close as possible. Nanoindentation was performed on the cluster to get the correct Young's moduli. The volumetric expansion associated with the formation of NiO was also included. It was found that the cracking of the CSN clusters is likely to occur during its last stage of formation as the last Ni-rich core oxidizes. Furthermore, it was shown that the volumetric expansion associated with the oxidation only plays a minor role and that the main reason for cracking is the high coefficient of thermal expansion of NiO.

  • 14.
    Eriksson, Robert
    et al.
    Siemens AG, Energy Sector, Berlin, Germany.
    Yuan, Kang
    Linköping University, Department of Management and Engineering. Linköping University, Faculty of Science & Engineering.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Corrosion of NiCoCrAIY Coatings and TBC Systems Subjected to Water Vapor and Sodium Sulfate2015In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 24, no 6, p. 953-964Article in journal (Refereed)
    Abstract [en]

    Thermal barrier coating (TBC) systems are commonly used in gas turbines for protection against high-temperature degradation. Penetration of the ceramic top coat by corrosive species may cause corrosion damage on the underlying NiCoCrAlY bond coat and cause failure of the TBC system. In the current study, four oxidation/corrosion conditions were tried: (i) lab air, (ii) water vapor, (iii) sodium sulfate deposited on the specimens, and (iv) water vapor + sodium sulfate. The test was done at 750 °C in a cyclic test rig with 48 h cycles. The corrosion damage was studied on NiCoCrAlY-coated specimens, thin APS TBC specimens, and thick APS TBC specimens. Water vapor was found to have very minor influence on the oxidation, while sodium sulfate increased the TGO thickness both for NiCoCrAlY specimens and TBC-coated specimens; the influence of the TBC thickness was found to be very small. Sodium sulfate promoted thicker TGO; more Cr-rich TGO; the formation of Y oxides, and internally, Y sulfides; pore formation in the coating as well as in the substrate; and the formation of a Cr-depleted zone in the substrate.

  • 15.
    Ganvir, Ashish
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Characterization of Microstructure and Thermal Properties of YSZ Coatings Obtained by Axial Suspension Plasma Spraying (ASPS)2015In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 24, no 7, p. 1195-1204Article in journal (Refereed)
    Abstract [en]

    The paper aims at demonstrating various microstructures which can be obtained using the suspension spraying technique and their respective significance in enhancing the thermal insulation property of a thermal barrier coating. Three different types of coating microstructures are discussed which were produced by the Axial Suspension Plasma Spraying. Detailed characterization of coatings was then performed. Optical and scanning electron microscopy were utilized for microstructure evaluations; x-ray diffraction for phase analysis; water impregnation, image analysis, and mercury intrusion porosimetry for porosity analysis, and laser flash analysis for thermal diffusivity measurements were used. The results showed that Axial Suspension Plasma Spraying can generate vertically cracked, porous, and feathery columnar-type microstructures. Pore size distribution was found in micron, submicron, and nanometer range. Higher overall porosity, the lower density of vertical cracks or inter-column spacing, and higher inter-pass porosity favored thermal insulation property of the coating. Significant increase in thermal diffusivity and conductivity was found at higher temperature, which is believed to be due to the pore rearrangement (sintering and pore coarsening). Thermal conductivity values for these coatings were also compared with electron beam physical vapor deposition (EBPVD) thermal barrier coatings from the literature and found to be much lower. © 2015 ASM International

  • 16.
    Ganvir, Ashish
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Joshi, Shrikant
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Vilemova, Monika
    IPP.
    Pala, Zdenek
    IPP.
    Influence of Microstructure on Thermal Properties of Axial Suspension Plasma-Sprayed YSZ Thermal Barrier Coatings2016In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 25, no 1-2, p. 202-212Article in journal (Refereed)
    Abstract [en]

    Suspension plasma spraying is a relatively new thermal spaying technique to produce advanced thermal barrier coatings (TBCs) and enables production of coatings with a variety of structures—highly dense, highly porous, segmented, or columnar. This work investigates suspension plasma-sprayed TBCs produced using axial injection with different process parameters. The influence of coating microstructure on thermal properties was of specific interest. Tests carried out included microstructural analysis, phase analysis, determination of porosity, and pore size distribution, as well as thermal diffusivity/conductivity measurements. Results showed that axial suspension plasma spraying process makes it possible to produce various columnar-type coatings under different processing conditions. Significant influence of microstructural features on thermal properties of the coatings was noted. In particular, the process parameter-dependent microstructural attributes, such as porosity, column density, and crystallite size, were shown to govern the thermal diffusivity and thermal conductivity of the coating.

  • 17.
    Ganvir, Ashish
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Kumara, Chamara
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Gupta, Mohit Kumar
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Nylen, Per
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Thermal Conductivity in Suspension Sprayed Thermal Barrier Coatings: Modeling and Experiments2017In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 26, no 1-2, p. 71-82Article in journal (Refereed)
    Abstract [en]

    Axial suspension plasma spraying (ASPS) can generate microstructures with higher porosity and pores in the size range from submicron to nanometer. ASPS thermal barrier coatings (TBC) have already shown a great potential to produce low thermal conductivity coatings for gas turbine applications. It is important to understand the fundamental relationships between microstructural defects in ASPS coatings such as crystallite boundaries, porosity etc. and thermal conductivity. Object-oriented finite element (OOF) analysis has been shown as an effective tool for evaluating thermal conductivity of conventional TBCs as this method is capable of incorporating the inherent microstructure in the model. The objective of this work was to analyze the thermal conductivity of ASPS TBCs using experimental techniques and also to evaluate a procedure where OOF can be used to predict and analyze the thermal conductivity for these coatings. Verification of the model was done by comparing modeling results with the experimental thermal conductivity. The results showed that the varied scaled porosity has a significant influence on the thermal conductivity. Smaller crystallites and higher overall porosity content resulted in lower thermal conductivity. It was shown that OOF could be a powerful tool to predict and rank thermal conductivity of ASPS TBCs.

  • 18.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Dwivedi, Gopal
    Stony Brook University, USA.
    Nylén, Per
    University West, Department of Engineering Science, Research Environment Production Technology West.
    Vackel, Andrew
    Stony Brook University, USA.
    Sampath, Sanjay
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    An Experimental Study of Microstructure: Property Relationships in Thermal Barrier Coatings2013In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 22, no 5, p. 659-670Article in journal (Refereed)
    Abstract [en]

    The thermal-mechanical properties of thermal barrier coatings are highly influenced by the defects present in coating microstructure. The aim of this study was to meet the future needs of the gas turbine industry by further development of zirconia coatings through the assessment of microstructure-property relationships. A design of experiments was conducted for this purpose with current, spray distance, and powder feed rate as the varied parameters. Microstructure was assessed with SEM and image analysis was used to characterize porosity content. Evaluations were carried out using laser flash technique to measure thermal properties. A bi-layer beam curvature technique in conjunction with controlled thermal cycling was used to assess the mechanical properties, in particular their nonlinear elastic response. Coating lifetime was evaluated by thermo-cyclic fatigue testing. Relationships between microstructure and coating properties are discussed. Dense vertically cracked microstructure and highly porous microstructure with large globular pores were also fabricated. Correlations between parameters obtained from nonlinear measurements and lifetime based on a priori established microstructural analysis were attempted in an effort to develop and identify a simplified strategy to assess coating durability following sustained long-term exposure to high temperature thermal cycling.

  • 19.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Kumara, Chamara
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Nylén, Per
    University West, Department of Engineering Science, Research Enviroment Production Technology West. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Bilayer Suspension Plasma-Sprayed Thermal Barrier Coatings with Enhanced Thermal Cyclic Lifetime: Experiments and Modeling2017In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 26, no 6, p. 1038-1051Article in journal (Refereed)
    Abstract [en]

    Suspension plasma spraying (SPS) has been shown as a promising process to produce porous columnar strain tolerant coatings for thermal barrier coatings (TBCs) in gas turbine engines. However, the highly porous structure is vulnerable to crack propagation, especially near the topcoat-bondcoat interface where high stresses are generated due to thermal cycling. A topcoat layer with high toughness near the topcoat-bondcoat interface could be beneficial to enhance thermal cyclic lifetime of SPS TBCs. In this work, a bilayer coating system consisting of first a dense layer near the topcoat-bondcoat interface followed by a porous columnar layer was fabricated by SPS using Yttria-stabilised zirconia suspension. The objective of this work was to investigate if the bilayer topcoat architecture could enhance the thermal cyclic lifetime of SPS TBCs through experiments and to understand the effect of the column gaps/vertical cracks and the dense layer on the generated stresses in the TBC during thermal cyclic loading through finite element modeling. The experimental results show that the bilayer TBC had significantly higher lifetime than the single-layer TBC. The modeling results show that the dense layer and vertical cracks are beneficial as they reduce the thermally induced stresses which thus increase the lifetime.

  • 20.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Li, X. -H
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Östergren, Lars
    GKN Aerospace, Trollhättan, Sweden.
    Influence of Bondcoat Spray Process on Lifetime of Suspension Plasma-Sprayed Thermal Barrier Coatings2018In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 27, no 1-2, p. 84-97Article in journal (Refereed)
    Abstract [en]

    Development of thermal barrier coatings (TBCs) manufactured by suspension plasma spraying (SPS) is of high commercial interest as SPS has been shown capable of producing highly porous columnar microstructures similar to the conventionally used electron beam–physical vapor deposition. However, lifetime of SPS coatings needs to be improved further to be used in commercial applications. The bondcoat microstructure as well as topcoat–bondcoat interface topography affects the TBC lifetime significantly. The objective of this work was to investigate the influence of different bondcoat deposition processes for SPS topcoats. In this work, a NiCoCrAlY bondcoat deposited by high velocity air fuel (HVAF) was compared to commercial vacuum plasma-sprayed NiCoCrAlY and PtAl diffusion bondcoats. All bondcoat variations were prepared with and without grit blasting the bondcoat surface. SPS was used to deposit the topcoats on all samples using the same spray parameters. Lifetime of these samples was examined by thermal cyclic fatigue testing. Isothermal heat treatment was performed to study bondcoat oxidation over time. The effect of bondcoat deposition process and interface topography on lifetime in each case has been discussed. The results show that HVAF could be a suitable process for bondcoat deposition in SPS TBCs.

  • 21.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Rocchio-Heller, R.
    Oerlikon Metco, Westbury, USA.
    Liu, J.
    Oerlikon Metco, Westbury, USA.
    Li, X. -H
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Östergren, L.
    GKN Aerospace, Trollhättan, Sweden.
    Failure Analysis of Multilayered Suspension Plasma-Sprayed Thermal Barrier Coatings for Gas Turbine Applications2018In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 27, no 3, p. 402-411-Article in journal (Refereed)
    Abstract [en]

    Improvement in the performance of thermal barrier coatings (TBCs) is one of the key objectives for further development of gas turbine applications. The material most commonly used as TBC topcoat is yttria-stabilized zirconia (YSZ). However, the usage of YSZ is limited by the operating temperature range which in turn restricts the engine efficiency. Materials such as pyrochlores, perovskites, rare earth garnets are suitable candidates which could replace YSZ as they exhibit lower thermal conductivity and higher phase stability at elevated temperatures. The objective of this work was to investigate different multilayered TBCs consisting of advanced topcoat materials fabricated by suspension plasma spraying (SPS). The investigated topcoat materials were YSZ, dysprosia-stabilized zirconia, gadolinium zirconate, and ceria–yttria-stabilized zirconia. All topcoats were deposited by TriplexPro-210TM plasma spray gun and radial injection of suspension. Lifetime of these samples was examined by thermal cyclic fatigue and thermal shock testing. Microstructure analysis of as-sprayed and failed specimens was performed with scanning electron microscope. The failure mechanisms in each case have been discussed in this article. The results show that SPS could be a promising route to produce multilayered TBCs for high-temperature applications.

  • 22.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Skogsberg, Kristoffer
    University West, Department of Engineering Science.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Influence of Topcoat-Bondcoat Interface Roughness on Stresses and Lifetime inThermal Barrier Coatings2014In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 23, no 1-2, p. 170-181Article in journal (Refereed)
    Abstract [en]

    Failure in Atmospheric Plasma Sprayed (APS) Thermal Barrier Coatings (TBCs) is associated with the thermo-mechanical stresses developing due to the Thermally Grown Oxide (TGO) layer growth and thermal expansion mismatch during thermal cycling. The interface roughness has been shown to play a major role in the development of these induced stresses and lifetime of TBCs. Modeling has been shown as an effective tool to understand the effect of interface roughness on induced stresses. In previous work done by our research group, it was observed that APS bondcoats performed better than the bondcoats sprayed with High Velocity Oxy-Fuel (HVOF) process which is contrary to the present literature data. The objective of this work was to understand this observed difference in lifetime with the help of finite element modeling by using real surface topographies. Different TGO layer thicknesses were evaluated. The modeling results were also compared with existing theories established on simplified sinusoidal profiles published in earlier works. It was shown that modeling can be used as an effective tool to understand the stress behavior in TBCs with different roughness profiles.

  • 23.
    Jafari, Reza
    et al.
    Tarbiat Modares University, Department of Material Science and Engineering, Tehran, Iran.
    Sadeghimeresht, Esmaeil
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Shahrabi Farahani, Taghi
    Tarbiat Modares University, Department of Material Science and Engineering, Tehran, Iran.
    Huhtakangas, Matti
    M. H. Engineering AB, Karlskoga, Sweden .
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    KCl-Induced High Temperature Corrosion Behavior of HVAF-Sprayed Ni-Based Coatings in Ambient Air2018In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 27, no 3, p. 500-511Article in journal (Refereed)
    Abstract [en]

    KCl-induced high temperature corrosion behavior of four HVAF-sprayed Ni-based coatings (Ni21Cr, Ni5Al, Ni21Cr7Al1Y, and Ni21Cr9Mo) under KCl deposit has been investigated in ambient air at 600°C up to 168h. The coatings were deposited onto 16Mo3 steel - a widely used boiler tube material.Uncoated substrate, 304L and Sanicro25 were used as reference materials in the test environment.SEM/EDS and XRD techniques were utilized to characterize the as-sprayed and exposed samples.The results showed that the small addition of KCl significantly accelerated degradation to the coatings. All coatings provided better corrosion resistance compared to the reference materials. The alumina-forming Ni5Al coating under KCl deposit was capable of forming a more protective oxide scale compared to the chromia-forming coatings as penetration of Cl through diffusion paths was hindered. Both active corrosion and chromate formation mechanisms were found to be responsible for Page 1 of 23ASM the corrosion damages. The corrosion resistance of the coatings based on the microstructure analysis and kinetics had the following ranking (from the best to worst): Ni5Al >Ni21Cr> Ni21Cr7Al1Y>Ni21Cr9Mo.

  • 24.
    Jiang, Janna
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Fasth, Angelica
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylen, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Choi, W.B.
    Center for Thermal Spray Research, Stony Brook, NY, USA.
    Microindentation and Inverse Analysis to Characterize Elastic-Plastic Properties for Thermal Sprayed Ti2AlC and NiCoCrAlY2009In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 18, no 2, p. 194-200Article in journal (Refereed)
    Abstract [en]

    Elastic-plastic material properties for HVOF sprayed Ti2AlC (sprayed with Maxthal 211 powder) and plasma sprayed NiCoCrAlY coatings were investigated using modeling and experimental Berkovich microindentation. Optical microstructure evaluations were also performed. The theories of Hertz, Oliver and Pharr were combined with finite element analysis for extracting the material properties. Empirically based material models for both thermal sprayed Ti2AlC and NiCoCrAlY coatings are proposed.

  • 25.
    Jonnalagadda, Krisha Praveen
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Mahade, Satyapal
    Department of Engineering ScienceUniversity West, Trollhättan, Sweden.
    Curry, Nicholas
    Treibacher Industrie AG, Althofen, Austria.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Markocsan, Nicolaie
    Department of Engineering Science University West, Trollhättan, Sweden.
    Nylén, Per
    Department of Engineering Science University West, Trollhättan, Sweden.
    Björklund, Stefan
    Department of Engineering Science University West, Trollhättan, Sweden.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Hot Corrosion Mechanism in Multi-Layer Suspension Plasma Sprayed Gd2Zr2O7 /YSZ Thermal Barrier Coatings in the Presence of V2O5 + Na2SO42017In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 26, no 1, p. 140-149Article in journal (Refereed)
    Abstract [en]

    This study investigates the corrosion resistance of two-layer Gd2Zr2O7/YSZ, three-layer dense Gd2Zr2O7/ Gd2Zr2O7/YSZ, and a reference single-layer YSZ coating with a similar overall top coat thickness of 300-320 µm. All the coatings were manufactured by suspension plasma spraying resulting in a columnar structure except for the dense layer. Corrosion tests were conducted at 900 °C for 8 h using V2O5 and Na2SO4 as corrosive salts at a concentration of approximately 4 mg/cm2. SEM investigations after the corrosion tests show that Gd2Zr2O7-based coatings exhibited lower reactivity with the corrosive salts and the formation of gadolinium vanadate (GdVO4), accompanied by the phase transformation of zirconia was observed. It is believed that the GdVO4 formation between the columns reduced the strain tolerance of the coating and also due to the fact that Gd2Zr2O7 has a lower fracture toughness value made it more susceptible to corrosion-induced damage. Furthermore, the presence of a relatively dense layer of Gd2Zr2O7 on the top did not improve in reducing the corrosion-induced damage. For the reference YSZ coating, the observed corrosion-induced damage was lower probably due to combination of more limited salt penetration, the SPS microstructure and superior fracture toughness of YSZ.

  • 26.
    Jonnalagadda, Krishna Praveen
    et al.
    Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Mahade, Satyapal
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Curry, Nicholas
    Treibacher Ind AG, Althofen, Austria.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Nylen, Per
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Hot Corrosion Mechanism in Multi-Layer Suspension Plasma Sprayed Gd2Zr2O7 /YSZ Thermal Barrier Coatings in the Presence of V2O5 + Na2SO42017In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 26, no 1-2, p. 140-149Article in journal (Refereed)
    Abstract [en]

    This study investigates the corrosion resistance of two-layer Gd2Zr2O7/YSZ, three-layer dense Gd2Zr2O7/ Gd2Zr2O7/YSZ, and a reference single-layer YSZ coating with a similar overall top coat thickness of 300-320 µm. All the coatings were manufactured by suspension plasma spraying resulting in a columnar structure except for the dense layer. Corrosion tests were conducted at 900 °C for 8 h using V2O5 and Na2SO4 as corrosive salts at a concentration of approximately 4 mg/cm2. SEM investigations after the corrosion tests show that Gd2Zr2O7-based coatings exhibited lower reactivity with the corrosive salts and the formation of gadolinium vanadate (GdVO4), accompanied by the phase transformation of zirconia was observed. It is believed that the GdVO4 formation between the columns reduced the strain tolerance of the coating and also due to the fact that Gd2Zr2O7 has a lower fracture toughness value made it more susceptible to corrosion-induced damage. Furthermore, the presence of a relatively dense layer of Gd2Zr2O7 on the top did not improve in reducing the corrosion-induced damage. For the reference YSZ coating, the observed corrosion-induced damage was lower probably due to combination of more limited salt penetration, the SPS microstructure and superior fracture toughness of YSZ.

  • 27.
    Jonnalagadda, Krishna Praveen
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Mahade, Satyapal
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Kramer, Stephanie
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Zhang, Pimin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Curry, Nicholas
    Treibacher Industrie AG, Althofen, Austria.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Failure of Multilayer Suspension Plasma Sprayed Thermal Barrier Coatings in the Presence of Na2SO4 and NaCl at 900 degrees C2019In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 28, no 1-2, p. 212-222Article in journal (Refereed)
    Abstract [en]

    The current investigation focuses on understanding the influence of a columnar microstructure and a sealing layer on the corrosion behavior of suspension plasma sprayed thermal barrier coatings (TBCs). Two different TBC systems were studied in this work. First is a double layer made of a composite of gadolinium zirconate+yttria stabilized zirconia (YSZ) deposited on top of YSZ. Second is a triple layer made of dense gadolinium zirconate deposited on top of gadolinium zirconate+YSZ over YSZ. Cyclic corrosion tests were conducted between 25 and 900 degrees C with an exposure time of 8h at 900 degrees C. 75wt.% Na2SO4+25wt.% NaCl were used as the corrosive salts at a concentration of 6mg/cm(2). Scanning electron microscopy analysis of the samples cross sections showed that severe bond coat degradation had taken place for both the TBC systems, and the extent of bond coat degradation was relatively higher in the triple-layer system. It is believed that the sealing layer in the triple-layer system reduced the number of infiltration channels for the molten salts which resulted in overflowing of the salts to the sample edges and caused damage to develop relatively more from the edge.

  • 28.
    Jonnalagadda, Krishna Praveen
    et al.
    Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Mahade, Satyapal
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Kramer, Stephanie
    Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Zhang, Pimin
    Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Curry, Nicholas
    Treibacher Industrie AG, Althofen, Austria.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB,Finspång,Sweden.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Failure of Multilayer Suspension Plasma Sprayed Thermal Barrier Coatings in the Presence of Na2SO4 and NaCl at 900 °C2019In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 28, no 1-2, p. 212-222Article in journal (Refereed)
    Abstract [en]

    The current investigation focuses on understanding the influence of a columnar microstructure and a sealing layer on the corrosion behavior of suspension plasma sprayed thermal barrier coatings (TBCs). Two different TBC systems were studied in this work. First is a double layer made of a composite of gadolinium zirconate + yttria stabilized zirconia (YSZ) deposited on top of YSZ. Second is a triple layer made of dense gadolinium zirconate deposited on top of gadolinium zirconate + YSZ over YSZ. Cyclic corrosion tests were conducted between 25 and 900 °C with an exposure time of 8 h at 900 °C. 75 wt.% Na2SO4 + 25 wt.% NaCl were used as the corrosive salts at a concentration of 6 mg/cm2. Scanning electron microscopy analysis of the samples’ cross sections showed that severe bond coat degradation had taken place for both the TBC systems, and the extent of bond coat degradation was relatively higher in the triple-layer system. It is believed that the sealing layer in the triple-layer system reduced the number of infiltration channels for the molten salts which resulted in overflowing of the salts to the sample edges and caused damage to develop relatively more from the edge.

  • 29.
    Jonnalagadda, Krishna Praveen
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Mahade, Satyapal
    Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Kramer, Stephanie
    Linköping University, Department of Management and Engineering. Linköping University, Faculty of Science & Engineering.
    Zhang, Pimin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Curry, Nicholas
    Treibacher Industrie AG, Althofen, Austria.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery AB,Finspång,Sweden.
    Peng, Ru Lin
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Failure of Multilayer Suspension Plasma Sprayed Thermal Barrier Coatings in the Presence of Na2SO4 and NaCl at 900 °C2019In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 28, no 1-2, p. 212-222Article in journal (Refereed)
    Abstract [en]

    The current investigation focuses on understanding the influence of a columnar microstructure and a sealing layer on the corrosion behavior of suspension plasma sprayed thermal barrier coatings (TBCs). Two different TBC systems were studied in this work. First is a double layer made of a composite of gadolinium zirconate + yttria stabilized zirconia (YSZ) deposited on top of YSZ. Second is a triple layer made of dense gadolinium zirconate deposited on top of gadolinium zirconate + YSZ over YSZ. Cyclic corrosion tests were conducted between 25 and 900 °C with an exposure time of 8 h at 900 °C. 75 wt.% Na2SO4 + 25 wt.% NaCl were used as the corrosive salts at a concentration of 6 mg/cm2. Scanning electron microscopy analysis of the samples’ cross sections showed that severe bond coat degradation had taken place for both the TBC systems, and the extent of bond coat degradation was relatively higher in the triple-layer system. It is believed that the sealing layer in the triple-layer system reduced the number of infiltration channels for the molten salts which resulted in overflowing of the salts to the sample edges and caused damage to develop relatively more from the edge.

  • 30. Joshi, S. V.
    et al.
    Sivakumar, G.
    Raghuveer, T.
    Dusane, R. O.
    Hybrid Plasma-Sprayed Thermal Barrier Coatings Using Powder and Solution Precursor Feedstock2014In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 23, no 4, p. 616-624Article in journal (Refereed)
    Abstract [en]

    A novel approach of hybridizing the conventional atmospheric plasma spraying (APS) technique with the solution precursor plasma spray (SPPS) route to achieve thermal barrier coatings (TBCs) with tailored configurations is presented. Such a hybrid process can be conveniently adopted for forming composite, multi-layered and graded coatings employing simultaneous and/or sequential feeding of solution precursor as well as powder feedstock, yielding distinct TBC microstructures that bear promise to further extend coating durability. TBC specimens generated using conventional APS technique, the SPPS method and through APS-SPPS hybrid processing have been comprehensively characterized for microstructure, phase constitution, hardness and thermal cycling life, and the results were compared to demonstrate the advantages that can ensue from hybrid processing.

  • 31.
    Kovářík, Ondrej
    et al.
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Haušild, Petr
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Medřický, Jan
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic..
    Tomek, Libor
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Siegl, Jan
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Mušálek, Radek
    Institute of Plasma Physics CAS.
    Nicholas, Curry
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Fatigue Crack Growth in Bodies with Thermally Sprayed Coating2016In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 25, no 1-2, p. 311-320Article in journal (Refereed)
    Abstract [en]

    Many applications of thermally sprayed coatings call for increased fatigue resistance of coated parts. Despite the intensive research in this area, the influence of coating on fatigue is still not completely understood. In this paper, the localization of crack initiation sites and the dynamics of crack propagation are studied. The resonance bending fatigue test was employed to test flat specimens with both sides coated. Hastelloy-X substrates coated with classical thermal barrier coating consisting of yttria stabilized zirconia and NiCoCrAlY layers. The strain distribution on the coating surface was evaluated by the Digital Image Correlation method through the whole duration of the fatigue test. Localization of crack initiation sites and the mode of crack propagation in the coated specimen are related to the observed resonance frequency. The individual phases of specimen degradation, i.e., the changes of material properties, crack initiation, and crack propagation, were identified. The tested coatings strongly influenced the first two phases, and the influence on the crack propagation was less significant. In general, the presented crack detection method can be used as a sensitive nondestructive testing method well suited for coated parts. © 2015 ASM International

  • 32.
    Kumar, S.
    et al.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad, India.
    Vidyasagar, V.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad,India.
    Jyothirmayi, A.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad, India.
    Joshi, Shrikant
    University West, Department of Engineering Science, Research Enviroment Production Technology West. International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad, India.
    Effect of Heat Treatment on Mechanical Properties and Corrosion Performance of Cold-Sprayed Tantalum Coatings2016In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 25, no 4, p. 745-756Article in journal (Refereed)
    Abstract [en]

    The cold-spray technique is of significant interest to deposit refractory metals with relatively high melting point for a variety of demanding applications. In the present study, mechanical properties of cold-sprayed tantalum coatings heat treated at different temperatures were investigated using microtensile testing, scratch testing, and nanoindentation. The corrosion performance of heat-treated coatings was also evaluated in 1 M KOH solution, and potentiodynamic polarization as well as impedance spectroscopy studies were carried out. Assessment of structure–property correlations was attempted based on microstructure, porosity, and intersplat bonding state, together with mechanical and corrosion properties of the heat-treated cold-sprayed tantalum coatings. Coatings annealed at 1500 °C, which is very close to the recrystallization temperature of tantalum, were found to perform almost as bulk tantalum, with exciting implications for various applications.

  • 33.
    Lemlikchi, Safia
    et al.
    Division milieu ionisés et lasers, Centre de Developpement des Technologies Avancees, Algiers, Algeria.
    Martinsson, Jesper
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Hamrit, Ahmed
    ALGESCO, Blida, Algeria.
    Djelouah, Hakim
    Universite´ des Sciences et de la Technologie Houari Boumediene, Algiers, Algeria.
    Asmani, Mohammed
    Université d’Alger 1, Algiers, Algeria.
    Carlson, Johan E.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Correction to: Ultrasonic Characterization of Thermally Sprayed Coatings2019In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 28, no 3, p. 591-Article in journal (Refereed)
    Abstract [en]

    The first name of author Ahmed Hamrit was misspelled as “Ahmet” in the original article. Please note that the correct spelling of his name is “Ahmed” as shown in this correction. 

  • 34.
    Lemlikchi, Safia
    et al.
    Division milieu ionisés et lasers, Centre de Developpement des Technologies Avancees, Algiers, Algeria.
    Martinsson, Jesper
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Hamrit, Ahmet
    ALGESCO, Blida, Algeria.
    Djelouah, Hakim
    Universite´ des Sciences et de la Technologie Houari Boumediene, Algiers, Algeria.
    Asmani, Mohammed
    Université d’Alger 1, Algiers, Algeria.
    Carlson, Johan E.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Ultrasonic Characterization of Thermally Sprayed Coatings2019In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 28, no 3, p. 391-404Article in journal (Refereed)
    Abstract [en]

    This paper describes the simultaneous determination of the ultrasonic parameters in thermally sprayed coatings. The parameters of interest are the longitudinal wave velocity and the ultrasonic attenuation. The test materials are two cobalt-based coatings (FSX 414 and Diamalloy 4060), both deposited onto stainless steel (310SS) substrates. The ultrasonic measurements were carried out in the pulse-echo configuration using several transducers. The ultrasonic signals reflected from the coatings were successfully estimated using the combined model, together with the maximum likelihood estimation and the Levenberg–Marquardt approach. The best estimate was obtained for 20 MHz measurements. Once the model was validated, the ultrasonic parameters of the thermally sprayed coatings were extracted. Model validation is based on the analysis of the residual between measured and estimated signals. Results showed non-dispersive ultrasonic velocities with average values of (3940±50)m/s" role="presentation" style="box-sizing: border-box; display: inline-table; line-height: normal; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">(3940±50)m/s(3940±50)m/s in Diamalloy 4060 and (4260±20)m/s" role="presentation" style="box-sizing: border-box; display: inline-table; line-height: normal; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">(4260±20)m/s(4260±20)m/s in FSX 414. High ultrasonic attenuation with a quadratic frequency dependence was observed for both materials. Moreover, it was found that the ultrasonic parameters in thermally sprayed materials are microstructure dependent. For close densities, the harder the coating, the higher the ultrasonic wave velocity and attenuation.

  • 35.
    Lyphout, Christophe
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Internal Diameter HVAF Spraying for Wear and Corrosion Applications2015In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 24, no 1-2, p. 235-243Article in journal (Refereed)
    Abstract [en]

    Electrolytic hard chrome (EHC) methods are still widely utilized in the printing, automotive and off-shore industries. Alternative methods to EHC have been widely developed in the past decade by conventional HVOF processes and more recently HVAF systems, which are processing at higher kinetic energy and more particularly at lower temperature, significantly increasing wear and corrosion resistance properties. A dedicated internal diameter HVAF system is here presented, and coatings characteristics are compared to the one obtained by standard HVAF coatings. Specially R&D designed fixtures with inside bore of 200 mm have been manufactured for this purpose, with a possibility to spray samples at increasing depth up to 400 mm while simulating closed bottom bore spraying. WC-based and Cr3C2-based powder feedstock materials have been deposited onto high-strength steel substrates. Respective coating microstructures, thermally induced stresses and corrosion resistance are discussed for further optimization of coating performances. The fact that the ID-HVAF system is utilized both for spraying and gritblasting procedures is also given a particular interest.

  • 36.
    Lyphout, Christophe
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Karlsson, M.
    Oerlikon Metco WOKA GmbH, Barchfeld-Immelborn, Germany.
    Runte, M
    Oerlikon Metco WOKA GmbH, Barchfeld-Immelborn, Germany.
    Reisel, G.
    Oerlikon Metco WOKA GmbH, Barchfeld-Immelborn, Germany.
    Boccaccio, P.
    University of Modena and Reggio Emilia, Modena, Italy .
    Screening Design of Supersonic Air Fuel Processing for Hard Metal Coatings2014In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 23, no 8, p. 1323-1332Article in journal (Refereed)
    Abstract [en]

    Replacement of electrolytic hard chromium method by thermal spray technology has shown a growing interest in the past decades, mainly pioneered by depositing WC-based material by conventional HVOF processes. Lower thermal energy and higher kinetic energy of sprayed particles achieved by newly developed Supersonic Air Fuel system, so-called HVAF-M3, significantly reduces decarburization, and increases wear and corrosion resistance properties, making HVAF-sprayed coatings attractive both economically and environmentally. In the present work, full factorial designs of experiments have been extensively utilized to establish relationships between hardware configurations, process and engineering variables, and coatings properties. The relevance of those process factors is emphasized and their significance is discussed in the optimization of coatings for improved abrasion wear and corrosion performances. © 2014 ASM International.

  • 37.
    Lyphout, Christophe
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Fasth, Angelica
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Mechanical Property of HVOF Inconel 718 Coating for Aeronautic Repair2014In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 23, no 3, p. 380-388Article in journal (Refereed)
    Abstract [en]

    The module of elasticity is one of the most important mechanical properties defining the strength of a material which is a prerequisite to design a component from its early stage of conception to its field of application. When a material is to be thermally sprayed, mechanical properties of the deposited layers differ from the bulk material, mainly due to the anisotropy of the highly textured coating microstructure. The mechanical response of the deposited layers significantly influences the overall performance of the coated component. It is, therefore, of importance to evaluate the effective module of elasticity of the coating. Conventional experimental methods such as microindentation, nanoindentation and four-point bending tests have been investigated and their results vary significantly, mainly due to inhomogeneous characteristics of the coating microstructure. Synchrotron radiation coupled with a tensile test rig has been proposed as an alternative method to determine the coating anisotropic elastic behavior dependence on crystallographic orientations. The investigation was performed on Inconel 718 (IN718) HVOF coatings sprayed on IN718 substrates. Combining these experimental techniques yield a deeper understanding of the nature of the HVOF coating Young’s modulus and thus a tool for Design Practice for repair applications. © 2013 ASM International.

  • 38.
    Lyphout, Christophe
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Manescu, A.
    Università Politecnica delle Marche, Ancona, Italy.
    Pirling, T.
    Laue-Langevin Institute (ILL), Grenoble, France.
    Erratum  Residual stresses distribution through thick HVOF sprayed inconel 718 coatings: (Journal of Thermal Spray Technology DOI: 10.1007/s11666-008-9242- 9)2011In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 20, no 5, p. 1140-Article in journal (Refereed)
  • 39.
    Lyphout, Christophe
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Manescu, A
    Università Politecnica delle Marche, Ancona, Italy.
    Pirling, T.
    Laue-Langevin Institute (ILL), Grenoble, France.
    Residual stresses distribution through thick HVOF sprayed inconel 718 coatings2008In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 17, no 5-6, p. 915-923Article in journal (Refereed)
  • 40.
    Lyphout, Christophe
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Östergren, L.G.
    Volvo Aero Corporation, Trollhättan.
    Adhesion strength of HVOF sprayed IN718 coatings2012In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 21, no 1, p. 86-95Article in journal (Refereed)
    Abstract [en]

    The adhesion strength of high-velocity oxyfuel thermally sprayed coatings is of prime importance when thick coatings are to be sprayed in repair applications. In this study, relationships between process parameters, particle in-flight characteristics, residual stresses, and adhesion strength were explored. The most important process parameters that influence HVOF sprayed IN718 coating adhesion strength on IN718 substrate material were identified. Residual stress distributions were determined using the modified layer removal method, and adhesion strength was measured using an in-house-developed tensile test. Relationships between process parameters, particle in-flight characteristics, coating microstructure, and adhesion strength were established. Particle temperature, particle velocity, substrate preparation, and deposition temperature were identified as critical parameters to attain high adhesion strength. Controlling these parameters can significantly improve the adhesion strength, thus enabling thick coatings to be sprayed for repair applications. © 2011 ASM International.

  • 41.
    Lyphout, Christophe
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Sato, K.
    Fujimi Incoporated.
    Houdkova, S.
    University of West Bohemia.
    Smazalova, E.
    University of West Bohemia.
    Lusvarghi, L.
    University of Modena and Reggio Emilia.
    Bolelli, G.
    University of Modena and Reggio Emilia.
    Sassatelli, P.
    University of Modena and Reggio Emilia.
    Tribological Properties of Hard Metal Coatings Sprayed by High-Velocity Air Fuel Process2016In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 25, no 1-2, p. 331-345Article in journal (Refereed)
    Abstract [en]

    Lowering the thermal energy and increasing the kinetic energyof hard metal particles sprayed by the newly developed HVAF systems can significantly reduce their decarburization, and increases the sliding wear and corrosion resistance of the resulting coatings, making the HVAF technique attractive, both economically and environmentally, over its HVOF predecessors. Two agglomerated and sintered feedstock powder chemistries, WC-Co (88/12) and WC-CoCr (86/10/4), respectively, with increasing primary carbides grain size from 0.2 to 4.0 microns, have been deposited by the latest HVAF-M3 process onto carbon steel substrates. Their dry sliding wear behaviors and friction coefficients were evaluated at room temperature via Ball-on-disk (ASTM G99-90) wear tests against Al<inf>2</inf>O<inf>3</inf> counterparts, and via Pin-on-disk (ASTM G77-05) wear tests against modified martensitic steel counterparts in both dry and lubricated conditions. Sliding wear mechanisms, with the formation of wavy surface morphology and brittle cracking, are discussed regarding the distribution and size of primary carbides. Corrosion behaviors were evaluated via standard Neutral Salt Spray, Acetic Acid Salt Spray, accelerated corrosion test, and electrochemical polarization test at room temperature. The optimization of the tribological properties of the coatings is discussed, focusing on the suitable selection of primary carbide size for different working load applications. © 2015 ASM International

  • 42.
    Mahade, Satyapal
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Curry, Nicholas
    Treibacher Industrie AGAlthofenAustria.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Nylén, Per
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Vaßen, Robert
    Institute of Energy and Climate Research (IEK-1) Forschungszentrum Jülich GmbHJülich Germany.
    Erosion Performance of Gadolinium Zirconate-Based Thermal Barrier Coatings Processed by Suspension Plasma Spray2017In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 26, no 1-2, p. 108-115Article in journal (Refereed)
    Abstract [en]

    7-8 wt.% Yttria-stabilized zirconia (YSZ) is the standard thermal barrier coating (TBC) material used by the gas turbines industry due to its excellent thermal and thermo-mechanical properties up to 1200 °C. The need for improvement in gas turbine efficiency has led to an increase in the turbine inlet gas temperature. However, above 1200 °C, YSZ has issues such as poor sintering resistance, poor phase stability and susceptibility to calcium magnesium alumino silicates (CMAS) degradation. Gadolinium zirconate (GZ) is considered as one of the promising top coat candidates for TBC applications at high temperatures (>1200 °C) due to its low thermal conductivity, good sintering resistance and CMAS attack resistance. Single-layer 8YSZ, double-layer GZ/YSZ and triple-layer GZdense/GZ/YSZ TBCs were deposited by suspension plasma spray (SPS) process. Microstructural analysis was carried out by scanning electron microscopy (SEM). A columnar microstructure was observed in the single-, double- and triple-layer TBCs. Phase analysis of the as-sprayed TBCs was carried out using XRD (x-ray diffraction) where a tetragonal prime phase of zirconia in the single-layer YSZ TBC and a cubic defect fluorite phase of GZ in the double and triple-layer TBCs was observed. Porosity measurements of the as-sprayed TBCs were made by water intrusion method and image analysis method. The as-sprayed GZ-based multi-layered TBCs were subjected to erosion test at room temperature, and their erosion resistance was compared with single-layer 8YSZ. It was shown that the erosion resistance of 8YSZ single-layer TBC was higher than GZ-based multi-layered TBCs. Among the multi-layered TBCs, triple-layer TBC was slightly better than double layer in terms of erosion resistance. The eroded TBCs were cold-mounted and analyzed by SEM.

  • 43.
    Markocsan, Nicolaie
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Gupta, Mohit Kumar
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Nylén, Per
    University West, Department of Engineering Science, Research Enviroment Production Technology West. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery, Finspång, Sweden.
    Wigren, Jan
    GKN Aerospace,Trollhättan,Sweden.
    Liquid Feedstock Plasma Spraying: An Emerging Process for Advanced Thermal Barrier Coatings2017In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 26, no 6, p. 1104-1114Article in journal (Refereed)
    Abstract [en]

    Liquid feedstock plasma spraying (LFPS) involves deposition of ultrafine droplets of suspensions or solution precursors (typically ranging from nano- to submicron size) and permits production of coatings with unique microstructures that are promising for advanced thermal barrier coating (TBC) applications. This paper reviews the recent progress arising from efforts devoted to development of high-performance TBCs using the LFPS approach. Advancements in both suspension plasma spraying and solution precursor plasma spraying, which constitute the two main variants of LFPS, are presented. Results illustrating the different types of the microstructures that can be realized in LFPS through appropriate process parameter control, model-assisted assessment of influence of coating defects on thermo-mechanical properties and the complex interplay between pore coarsening, sintering and crystallite growth in governing thermal conductivity are summarized. The enhancement in functional performances/lifetime possible in LFPS TBCs with multilayered architectures and by incorporating new pyrochlore chemistries such as gadolinium zirconate, besides the conventional single 8 wt.% yttria-stabilized zirconia insulating ceramic layer, is specifically highlighted.

  • 44.
    Markocsan, Nicolaie
    et al.
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Nylén, Per
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Turunen, Erja
    Tampere University of Technology.
    Vuoristo, Petri
    Tampere University of Technology.
    Wigren, Jan
    Volvo Aero Corporation, Trollhättan.
    Thermal spraying in Europe’s Nordic region2007In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 16, no 4, p. 463-464Article in journal (Refereed)
  • 45.
    Markocsan, Nicolaie
    et al.
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Nylén, Per
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Wigren, Jan
    Volvo Aero Corporation, Surface Technology,Trollhättan.
    Li, X.-H
    Siemens Industrial Turbomachinery,Department of GRDM, Finspång.
    Low thermal conductivity coatings for gas turbine applications2007In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 16, no 4, p. 498-505Article in journal (Refereed)
  • 46.
    Medricky, Jan
    et al.
    Czech Technical University in Prague, Prague, Czech Republic.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Pala, Zdenek
    Institute of Plasma Physics AS CR, Prague, Czech Republic.
    Vilemova, Monika
    Institute of Plasma Physics AS CR, Prague, Czech Republic.
    Chraska, Tomas
    Institute of Plasma Physics AS CR, Prague, Czech Republic.
    Johansson, Jimmy
    GKN Aerospace Engine Systems, Trollhättan, Darrasa, Sweden.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Optimization of High Porosity Thermal Barrier Coatings Generated with a Porosity Former2015In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 24, no 4, p. 622-628Article in journal (Refereed)
    Abstract [en]

    Yttria-stabilized zirconia thermal barrier coatings are extensively used in turbine industry; however, increasing performance requirements have begun to make conventional air plasma sprayed coatings insufficient for future needs. Since the thermal conductivity of bulk material cannot be lowered easily; the design of highly porous coatings may be the most efficient way to achieve coatings with low thermal conductivity. Thus the approach of fabrication of coatings with a high porosity level based on plasma spraying of ceramic particles of dysprosia-stabilized zirconia mixed with polymer particles, has been tested. Both polymer and ceramic particles melt in plasma and after impact onto a substrate they form a coating. When the coating is subjected to heat treatment, polymer burns out and a complex structure of pores and cracks is formed. In order to obtain desired porosity level and microstructural features in coatings; a design of experiments, based on changes in spray distance, powder feeding rate, and plasma-forming atmosphere, was performed. Acquired coatings were evaluated for thermal conductivity and thermo-cyclic fatigue, and their morphology was assessed using scanning electron microscopy. It was shown that porosity level can be controlled by appropriate changes in spraying parameters.

  • 47.
    Musalek, Radek
    et al.
    Institute of Plasma Physics AS CR, Department of Materials Engineering , v.v.i, Za Slovankou 3, 182 00, Praha 8, Czech Republic.
    Kovarik, Ondrej
    Czech Technical University in Prague, Department of Materials, Faculty of Nuclear Sciences and Physical Engineering, Trojanova 13, 120 00, Praha 2, Czech Republic.
    Medricky, Jan
    Czech Technical University in Prague, Department of Materials, Faculty of Nuclear Sciences and Physical Engineering, Trojanova 13, 120 00, Praha 2, Czech Republic.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nylén, Per
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Fatigue Testing of TBC on Structural Steel by Cyclic Bending2015In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 24, no 1-2, p. 168-174Article in journal (Refereed)
    Abstract [en]

    For applications with variable loading, fatigue performance of coated parts is of utmost importance. In this study, fatigue performance of conventional structural steel coated with thermal barrier coating (TBC) was evaluated in cyclic bending mode by “SF-Test” device. Testing was carried out at each stage of the TBC preparation process, i. e., for as-received and grit-blasted substrates, as well as for samples with Ni-based bond-coat and complete TBC: bond-coat with YSZ-based top-coat. Comparison of results obtained for different loading amplitudes supplemented by fractographic analysis enabled identification of dominating failure mechanisms and demonstrated applicability of the high-frequency resonant bending test for evaluation of fatigue resistance alteration at each stage of the TBC deposition process.

  • 48.
    Musalek, Radek
    et al.
    Institute of Plasma Physics AS CR, Department of Materials Engineering, v.v.i..
    Kovarik, Ondrej
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Tomek, Libor
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Medricky, Jan
    Institute of Plasma Physics AS CR, Department of Materials Engineering, v.v.i..
    Pala, Zdenek
    Institute of Plasma Physics AS CR, Department of Materials Engineering, v.v.i..
    Hausild, Petr
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Department of Materials.
    Capek, Jiri
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Department of Solid State Engineering.
    Kolarik, Kamil
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Department of Solid State Engineering.
    Nicholas, Curry
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Fatigue Performance of TBCs on Hastelloy X Substrate During Cyclic Bending2016In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 25, no 1-2, p. 231-243Article in journal (Refereed)
    Abstract [en]

    Our previous experiments with low-cost steel substrates confirmed that individual steps of conventional thermal barrier coating (TBC) deposition may influence fatigue properties of the coated samples differently. In the presented study, testing was carried out for TBC samples deposited on industrially more relevant Hastelloy X substrates. Samples were tested after each step of the TBC deposition process: as-received (non-coated), grit-blasted, bond-coated (NiCoCrAlY), and bond-coated + top-coated yttria-stabilized zirconia (YSZ). Conventional atmospheric plasma spraying (APS) was used for deposition of bond coat and top coat. In addition, for one half of the samples, dual-layer bond coat was prepared by combination of high-velocity air-fuel (HVAF) and APS processes. Samples were tested in the as-sprayed condition and after 100 hours annealing at 980 °C, which simulated application-relevant in-service conditions. Obtained results showed that each stage of the TBC manufacturing process as well as the simulated in-service heat exposure may significantly influence the fatigue properties of the TBC coated part. HVAF grit-blasting substantially increased the fatigue performance of the uncoated substrates. This beneficial effect was suppressed by deposition of APS bond coat but not by deposition of dual-layer HVAF + APS bond coat. All heat-treated samples showed again enhanced fatigue performance. © 2015 ASM International

  • 49. Nylen, Per
    et al.
    Hansbo, Anita
    Friis, Martin
    Pejryd, Lars
    Investigation of particle in-flight characteristics during atmospheric plasma spraying of yttria stabilized ZrO2: Part 2. Modeling2001In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 10, no 2, p. 359-366Article in journal (Refereed)
    Abstract [en]

    Yttria stabilized ZrO2 particle in-flight characteristics in an Ar-H2 atmospheric plasma jet have been studied using analytical and experimental techniques. In the previous article,[1] the primary gas flow, plasma composition, current, and powder feed rate were systematically varied and particle surface temperatures, velocities, and size distributions measured and statistically analyzed. In this paper, a mathematical model for the plasma flow and particle characteristics is presented. Model predictions are compared with the experimental results in Ref 1 and a reasonable correlation is found. A statistical investigation (composite cubic face (CCF)) is performed on the particle predictions, giving fast and simple relationships between gun parameters and particle in-flight properties. The statistical and theoretical models that are presented here combine to form a powerful and cost-effective tool, which can be used in the evaluation and optimization of spray parameters off-line.

  • 50. Raman, S. G. S.
    et al.
    Raiasekaran, B.
    Joshi, S. V.
    Sundararajan, G.
    Influence of substrate material on plain fatigue and fretting fatigue behavior of detonation gun sprayed Cu-Ni-In coating2007In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 16, no 4, p. 571-579Article in journal (Refereed)
    Abstract [en]

    Cu-Ni-In coating was formulated on two substrate materials-Ti-alloy (Ti-6Al-4V) and Al-alloy (AA 6063) fatigue test specimens using detonation gun (D-gun) spray process. Coating on both substrates was dense with low porosity, high hardness, and high surface roughness. Relatively higher surface compressive residual stress was present at the coating on Ti-alloy specimens. In case of the coating on Al-alloy samples, tensile residual stress was also present in some places. Uniaxial plain fatigue and fretting fatigue experiments were conducted on uncoated and coated specimens. The detrimental effect of life reduction due to fretting was relatively larger in the Al-alloy compared to the Ti-alloy. While Cu-Ni-In coating was found to be beneficial on the Ti-alloy, it was deleterious on the Al-alloy substrate under both plain fatigue and fretting fatigue loading. The results were explained in terms of differences in the values of surface hardness, surface roughness, surface residual stress, and friction stress.

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