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  • 1.
    Akhtar, Farid
    Institute of Powder Metallurgy, University of Science & Technology, Beijing.
    A new method to process high strength TiCN stainless steel matrix composites2007In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 50, no 3, p. 250-254Article in journal (Refereed)
    Abstract [en]

    Layered composites of Ti(C, N) reinforcements and stainless steel have been prepared successfully by powder technology. The layer composite consisted of two layers. The upper layer consisted of TiCN reinforcements and stainless steel as binder material. The lower layer was entirely of binder material (stainless steel). The micro structural study revealed that the upper layer (TiCN/465 stainless steel) showed core–rim microstructure of conventional cermets and the lower layer showed the structure of sintered steel. An intermediate layer was formed due to diffusion reaction of upper and lower layers. This intermediate layer showed a gradient microstructure. The bending strength of the layered material measured was remarkably higher. Ninety per cent increase in the bending strength in the case of 50 wt-% reinforcement in the upper layer was found. The fracture morphologies of upper, lower and intermediate layers are also reported

  • 2.
    Akhtar, Farid
    et al.
    Institute of Powder Metallurgy, Materials Science Department, University of Science and Technology Beijing.
    Guo, SJ
    Institute of Powder Metallurgy, Materials Science Department, University of Science and Technology Beijing.
    Shah, KA
    Institute of Powder Metallurgy, Materials Science Department, University of Science and Technology Beijing.
    Effect of Cu3P addition on sintering behaviour of elemental powders in the composition of 465 stainless steel2006In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 49, no 1, p. 28-33Article in journal (Refereed)
    Abstract [en]

    The addition of Cu3P for developing the high strength 465 maraging stainless steel from elemental powders was studied. The sintering parameters investigated were sintering temperature, sintering time and wt-%Cu3P. In vacuum sintering, effective sintering took place between 1300 and 1350°C. The maximum sintered density of 7·44 g cm−3 was achieved at 1350°C for 60 min with 4–6 wt-%Cu3P. More than 6 wt-%Cu3P content and temperature >1350°C caused slumping of the specimens. The sintered specimens were heat treated and a maximum ultimate tensile strength (UTS) of 767 MPa was achieved with 4 wt-%Cu3P content. The maximum hardness of 45·5 HRC was achieved in heat treated condition with 4 wt-%Cu3P content. Above 4 wt-%Cu3P content increase in density was observed whereas the response to heat treatment decreased. Fracture morphologies of the sintered specimens were also reported. A comparison of sintering behaviour and mechanical properties of elemental powders with prealloyed powders was also given in the present study

  • 3.
    Angré, Alexander
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea KIMAB.
    Ahlfors, Magnus
    QuintusTechnologies AB, Sweden.
    Chasoglou, Dimitri
    Höganäs AB, Sweden.
    Larsson, Linn
    AB Sandvik Technologies Material, Sweden.
    Claesson, Erik
    RISE - Research Institutes of Sweden, Swerea, Swerea KIMAB.
    Karlsson, Oskar
    RISE - Research Institutes of Sweden, Swerea, Swerea KIMAB.
    Phase transformation under isostatic pressure in HIP2017In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 60, no 3, p. 167-174Article in journal (Refereed)
    Abstract [en]

    The new HIP cooling systems enable very fast cooling rates under isostatic pressure. This does not only enable shorter HIP cycles but also allows complete heat treatment cycles to be performed in one HIP cycle. It has been shown in previous studies that extreme pressures of several thousand bar can push phase transformation towards longer times. The new URQ HIP cooling systems give the opportunity to investigate the impact of pressures up to 2000 bar on phase transformation time dependency. For each of the two materials in this study, a comparison of austenite phase transformation time at 100 and 1700 bar was performed. The study was performed by isothermal heat treatment of specimens for a specific time followed by quenching. To evaluate the influence of pressure on hardenability, the phase fractions were evaluated using grid method on SEM images. The study found significant influence of HIP pressure on hardenability.

  • 4.
    Arén, Björn
    et al.
    Luleå tekniska universitet.
    Navara, Eric
    Luleå tekniska universitet.
    Modelling shape change of parts produced by hot isostatic pressing1988In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 31, no 2, p. 101-105Article in journal (Refereed)
    Abstract [en]

    Models for analysing shape changes during the hipping of powder compacts enclosed in preshaped containers are presented. Two limiting mechanisms are considered: homogeneous densification and the motion of a sharply defined densification front through the compact as hipping proceeds. The shape changes and shrinkages occurring in a number of simple one, two, and three dimensional shapes are analysed and illustrated. Although some of the assumptions implicit in the model are at variance with the conditions found in practice, it is concluded that useful insights are provided into the shape changes occurring during hipping

  • 5.
    Arén, Björn
    et al.
    Luleå tekniska universitet.
    Navara, Eric
    Luleå tekniska universitet.
    Modelling shape change of parts produced by hot isostatic pressing of powders1988In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 31, no 2, p. 101-105Article in journal (Refereed)
    Abstract [en]

    Models for analysing shape changes during the HIPping of powder compacts enclosed in preshaped containers are presented. Two limiting mechanisms are considered: homogeneous densification and the motion of a sharply defined densification front through the compact as HIPping proceeds. The shape changes and shrinkages occurring in a number of simple one, two, and three dimensional shapes are analysed and illustrated. Although some of the assumptions implicit in the model are at variance with the conditions found in practice, it is concluded that useful insights are provided into the shape changes occurring during HIPping

  • 6.
    Arén, Björn
    et al.
    Luleå tekniska universitet.
    Nilsson, Annika
    Luleå tekniska universitet.
    Die tool dimensioning by finite element method1987In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 30, no 2, p. 87-96Article in journal (Refereed)
    Abstract [en]

    Stress and strain are studied using the finite element method in the dimensioning of prestrained die tools for powder compaction. The die geometry has been varied and the die has also been subjected to different types of load. The study shows that the mean pressure transverse to the pressing direction is a dimensioning factor, but that the distribution itself is not very important. For a linear pressure distribution, the stress and strain within the die will differ little from results produced under the assumption of an exponential pressure distribution. Attention is also paid to the possibilities of treating the three-dimensional situation in a real die by different methods of two-dimensional FEM analysis

  • 7.
    Bergman, Ola
    Product Innovation, Höganäs AB.
    Influence of oxygen partial pressure in sintering atmosphere on properties of Cr-Mo prealloyed powder metallurgy steel2007In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 50, no 3, p. 243-249Article in journal (Refereed)
    Abstract [en]

    Chromium is an attractive alloying element in low alloyed steels since it gives good hardenability at low cost. The drawback with using chromium in powder metallurgy ( PM) grades is its high affinity for oxygen. Thermodynamic calculations show that the oxygen partial pressure should be <4 x 10(-18) atm at 1120 degrees C in order to have reducing conditions for a powder grade prealloyed with 3 wt-%Cr and 0 center dot 5 wt-%Mo, which is supported by sintering experiments. With graphite added to the powder grade, conditions are reducing during sintering at higher partial pressures of oxygen ( up to 10 216 atm) due to favourable conditions locally in the material. Sintering of the powder grade with 0 center dot 35 wt-% graphite added at 1120 degrees C for 30 min at reducing conditions leads to high mechanical properties, although kinetics is insufficient for complete reduction of chromium oxides. At 1250 degrees C, kinetics is faster and practically all oxides are reduced after sintering for 30 min, with enhanced mechanical performance as result.

  • 8.
    Bergquist, B
    Linkoping Univ, Dept Mech Engn, Div Engn Mat, SE-58183 Linkoping, Sweden.
    Factor analysis of iron-phosphorus PM steel2000In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 43, no 2, p. 143-148Article in journal (Refereed)
    Abstract [en]

    Alloy design and choice of process parameters are often tasks where different investigations lead in different directions and the process of selecting the best parameter settings is difficult. Multivariate statistics are capable of bringing order in such situations, and here data from four different investigations on the Fe-P-C system are collected and evaluated. Effects of chemical composition, compaction pressure: sintering time, and sintering temperature on properties including density, tensile strength, impact energy, proof stress, and elongation are studied. The investigation is based on principal factor analysis. Dimensional reduction is presented and discussed. The study compares the different investigations and the results for the Fe-P-C system show how different properties interact.

  • 9.
    Bergquist, B
    Linkoping Univ, Div Engn Mat, Dept Engn Mech, SE-58183 Linkoping, Sweden.
    New insights into influencing variables of water atomisation of iron1999In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 42, no 4, p. 331-343Article in journal (Refereed)
    Abstract [en]

    Trace amounts of surfactants have an acute influence on measured surface tension of melts and may influence viscosity. A water atomisation experiment was performed to investigate if variations of these elements could affect quality. Effects of water pressure, melt superheat, and sulphur content, iron scrap oxygen content, and aluminium content were studied. Responses studied were particle size distribution, apparent density, flow, powder chemistry, morphology, green density, and dimensional change. A large sulphur addition reduced the particle size, as a result of a reduction of surface tension, but the largest effect came from changing water pressure. Higher water pressures also resulted in powders with lower apparent density, lower flowrate, and reduced swelling during sintering. An empirical water atomisation model is proposed. Aluminium additions reduced the powder size standard deviation and increased the carbon content of the powder. A reduced powder size standard deviation was seen also for melts with raised superheating. PM/0846 (C) 1999 IoM Communications Ltd.

  • 10.
    Bergquist, B
    et al.
    Lulea Tekniska Univ, Div Qual Technol & Stat, Dept Business Adm & Social Sci, SE-97187 Lulea, Sweden Linkoping Univ, Div Engn Mat, Dept Mech Engn, SE-58183 Linkoping, Sweden.
    Ericsson, Torsten
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Engineering Materials .
    Robustness simulation of water atomisation2000In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 43, no 1, p. 37-42Article in journal (Refereed)
    Abstract [en]

    One of the main purposes of water atomisation is to keep the powder size distribution within a close range. The process is difficult to monitor and thus the state of today's process control is poor. To investigate this process, both a laboratory scale and an industrial scale atomisation facility were modelled where melt flow and thermal flow were investigated. The results showed that metal temperature is important if stable particle sizes are to be obtained from batch to batch.

  • 11.
    Bergquist, Bjarne
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Business Administration and Industrial Engineering.
    Factor analysis of iron-phosphorus PM steel2000In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 43, no 2, p. 143-148Article in journal (Refereed)
    Abstract [en]

    Alloy design and choice of process parameters are often tasks where different investigations lead in different directions and the process of selecting the best parameter settings is difficult. Multivariate statistics are capable of bringing order in such situations, and here data from four different invesigations on the Fe-P-C system are collected and evaluated. Effects of chemical composition, comapction pressure, sintering time, and sintering temperature on properties including density, tensile strength, impact energy, proof stress, and elongation are studied. The investigation is based on principal factor analysis. Dimensional reduction is presented and discussed. The study compares the different investigations and the results for the Fe-P-C system show how different properties interact.

  • 12.
    Bergquist, Bjarne
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Business Administration and Industrial Engineering.
    New insights into influencing variables of water atomization of iron1999In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 42, no 4, p. 331-343Article in journal (Refereed)
    Abstract [en]

    Trace amounts of surfactants have an acute influence on measured surface tension of melts and may influence viscosity. A water atomisation experiment was performed to investigate if variations of these elements could affect quality. Effects of water pressure, melt superheat, and sulphur content, iron scrap oxygen content, and aluminium content were studied. Responses studied were particle size distribution, apparent density, flow, powder chemistry, morphology, green density, and dimensional change. A large sulphur addition reduced the particle size, as a result of a reduction of surface tension, but the largest effect came from changing water pressure. Higher water pressures also resulted in powders with lower apparent density, lower flowrate, and reduced swelling during sintering. An empirical water atomisation model is proposed. Aluminium additions reduced the powder size standard deviation and increased the carbon content of the powder. A reduced powder size standard deviation was seen also for melts with raised superheating.

  • 13.
    Bergquist, Bjarne
    et al.
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Business Administration and Industrial Engineering.
    Ericsson, T.
    Division of Engineering Materials, Department Mechanical Engineering, Linköpings universitet.
    Robustness simulation of water atomisation2000In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 43, no 1, p. 37-42Article in journal (Refereed)
    Abstract [en]

    One of the main purposes of water atomisation is to keep the powder size distribution within a close range. The process is difficult to monitor and thus the state of today's process control is poor. To investigate this process, both a laboratory scale and an industrial scale atomisation facility were modelled where melt flow and thermal flow were investigated. The results showed that metal temperature is important if stable particle sizes are to be obtained from batch to batch.

  • 14.
    Bergquist, Bjarne
    et al.
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Business Administration and Industrial Engineering.
    Hjortsberg, E.
    Chalmers University of Technology.
    Filling induced density variations in metal powder2002In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 45, no 2, p. 146-153Article in journal (Refereed)
    Abstract [en]

    Filling induced density variations is a problem that has long been overlooked by powder metallurgy scientists. In this paper,densityvariations are addressed, both why they occur and what problems they may cause. A test method, including a test rig, is presented that is able to link several different factors to resulting powder densities. The relations are analysed and several density affecting mechanisms are suggested. These mechanisms could be used either to minimise density differences within parts or to control density by directing powder to critical areas.

  • 15. El-Geassy, A. A.
    et al.
    Nassir, Nassier Abdul
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Ahmed, H. M.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Simultaneous reduction nitridation for the synthesis of tungsten nitrides from Ni-W-O precursors2013In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 56, no 5, p. 411-419Article in journal (Refereed)
    Abstract [en]

    Tungsten nitrides were synthesised from NiO-WO3 and NiWO 4 precursors at 973-1273 K in a flow of H2-N2 gas mixture. The reduction-nitridation reactions were carried out isothermally in fluidised bed reactor, and the off-gas from the reactions was continuously analysed by gas chromatography. The effect of reaction temperature and precursor composition on the rate of formation of Ni-W nitrides was studied. The different phases developed during the reduction-nitridation reactions were identified by X-ray diffraction analysis technique. The morphology and the grain structure of the precursors were examined by SEM, and the elemental composition in the structure was analysed by electron dispersive spectrometry. The results showed that the reduction of Ni-W-O precursors proceeded in a stepwise manner (NiWO4→Ni-WO3→Ni-WO2→Ni-W). Tungsten nitrides (WN and WN2) were formed from the reaction of the freshly reduced W metal with N2 gas and WN was the predominant phase detected at higher temperatures. The reaction mechanisms were elucidated from the apparent activation energy values and the application of different formulations derived from the gas-solid reaction model at early and later stages of reactions. It was concluded that the interfacial chemical reaction is the rate determining step at initial stages, while a combined effect of gaseous diffusion and interfacial chemical reaction controlled the reaction at later stages. At final stages, the nitridation reactions contributed to the reaction mechanism leading to produce tungsten nitrides.

  • 16.
    Eliasson, Anders
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Ceramics.
    Ekbom, L.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    Tungsten grain separation during initial stage of liquid phase sintering2008In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 51, no 4, p. 343-349Article in journal (Refereed)
    Abstract [en]

    The initial stage, the first few seconds of liquid phase sintering has been investigated in experiments using a tungsten heavy alloy with low tungsten content. The heavy alloy has been melted in a temperature gradient for short periods, similar to 9 s in an ellipsoid mirror furnace. During the liquid phase sintering at about 1470 degrees C, a penetration followed by a remarkably rapid separation and dispersion of the tungsten grains by the molten matrix occur. The suggested explanation for this grain separation and dispersion is based on the effect of composition gradients in the liquid matrix and a theory based on interagglomerate melt swelling due to a Kirkendall effect.

  • 17. Eriksson, Magnus
    et al.
    Häggblad, Hans-åke
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Berggren, C.
    Nobel Biocare AB.
    Andersson, M.
    Nobel Biocare AB.
    Holmersson, R.
    Nobel Biocare AB.
    Carlström, E.
    Swedish Ceramic Institute, PO Box 5403, SE-402 29 Göteborg.
    New semi-isostatic high velocity compaction method to prepare titanium dental copings2004In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 47, no 4, p. 335-342Article in journal (Refereed)
    Abstract [en]

    A new method to prepare titanium dental copings from titanium powder was tested, involving high velocity compaction and various elastic forms, which were used to achieve a semi-isostatic effect during the impact. The tooth preparation die (mandrel) and the powder were placed inside an elastic form. The impact struck the elastic form, and the powder was compacted against the tooth preparation die. Several different elastomers were tested to find the best one. Cross-sections of the powder bodies were studied for density variations. The soft, flexible elastomer worked best to compact the powder. The highest densification could be focused closest to the mandrel where the coping should be milled out. The density in the highest density areas could locally reach 98-99%. If the method with elastic forms could be optimised to give as high a density as without elastic forms, a lower shrinkage and possible deformation of the copings could be reached.

  • 18. Federzoni, L.
    et al.
    Riedel, H.
    Coube, O.
    Oldenburg, Mats
    Häggblad, Hans-åke
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Gethin, D.
    State of the art review - Comparison of computer models representing powder compaction process.1999In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 42, no 4, p. 301-311Article in journal (Refereed)
  • 19.
    Frisk, Karin
    et al.
    RISE, Swerea, Swerea KIMAB.
    Luo, Chunhui
    RISE, Swerea, Swerea KIMAB.
    Johansson, S.C.
    RISE, Swerea, Swerea KIMAB.
    Haglund, Sven
    RISE, Swerea, Swerea KIMAB.
    Petterson, Niklas
    RISE, Swerea, Swerea KIMAB.
    Strandell, I.
    AB SKF.
    Compound materials by PM-HIP2014In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 57, no 5, p. 341-347Article in journal (Refereed)
    Abstract [en]

    There are many applications where compound materials can be of interest, for example when different properties are needed in different parts of a component. Compound materials can be produced by hot isostatic pressing (HIP) of powder metallurgical materials. One aspect that should be considered in the design is the quality of the interface between the two different material compositions. Diffusion during HIP can cause formation of brittle phases in the interface or deteriorate properties by diffusion of alloying elements. The present work shows results from a study where different steel types were joined (quench and temper steel/air hardening steel/bearing steel with a tool steel/corrosion resistant martensitic steel). The evaluation was performed by computational predictions and by small scale HIP experiments that were evaluated by microstructure analysis and chemical analysis. © 2014 Institute of Materials, Minerals and Mining.

  • 20.
    Geassy, Abdel Hady El
    et al.
    Central Metallurgical Research and Development Institute (CMRDI), Helwan, Cairo.
    Nassir, Nassir
    Royal Institute of Technology, Stockholm.
    Ahmed, Hesham
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Seetharaman, Sishadri
    Royal Institute of Technology, Stockholm.
    Simultaneous reduction nitridation for the synthesis of tungsten nitrides from Ni–W–O precursors2013In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 56, no 5, p. 411-419Article in journal (Refereed)
    Abstract [en]

    Tungsten nitrides were synthesised from NiO–WO3 and NiWO4 precursors at 973–1273 K in a flow of H2–N2 gas mixture. The reduction–nitridation reactions were carried out isothermally in fluidised bed reactor, and the off-gas from the reactions was continuously analysed by gas chromatography. The effect of reaction temperature and precursor composition on the rate of formation of Ni–W nitrides was studied. The different phases developed during the reduction– nitridation reactions were identified by X-ray diffraction analysis technique. The morphology and the grain structure of the precursors were examined by SEM, and the elemental composition in the structure was analysed by electron dispersive spectrometry. The results showed that the reduction of Ni–W–O precursors proceeded in a stepwise manner (NiWO4RNi–WO3RNi– WO2RNi–W). Tungsten nitrides (WN and WN2) were formed from the reaction of the freshly reduced W metal with N2 gas and WN was the predominant phase detected at higher temperatures. The reaction mechanisms were elucidated from the apparent activation energy values and the application of different formulations derived from the gas–solid reaction model at early and later stages of reactions. It was concluded that the interfacial chemical reaction is the rate determining step at initial stages, while a combined effect of gaseous diffusion and interfacial chemical reaction controlled the reaction at later stages. At final stages, the nitridation reactions contributed to the reaction mechanism leading to produce tungsten nitrides.

  • 21.
    Gedda, Hans
    et al.
    Luleå tekniska universitet.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Rüstig, Katja
    Material Science and Materials Technology, Technische Universitat Bergakademie, Freiberg.
    Laser wire casting2003In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 46, no 3, p. 199-201Article in journal (Refereed)
    Abstract [en]

    A new technique has been developed for the production of solid wire or rods from powder by laser melting. Three techniques have been developed to ensure that the molten powder solidifies as a rod or wire rather than a series of droplets. The straight rods or wires produced in this way have near-circular cross-section, are several millimetres in diameter and can be pore free. The techniques can be used to produce welding rods, tensile test samples and other solid pieces from a wide range of powder mixes. The rapid thermal cycle involved means that it is now possible to produce hitherto difficult mixtures and alloys in the solid form in seconds.

  • 22. Harlin, P.
    et al.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Starch consolidation of M3/2 high speed steel powder: Influence of microstructure on mechanical properties2007In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 50, no 3, p. 232-238Article in journal (Refereed)
    Abstract [en]

    The influence of microstructure on the mechanical properties of starch consolidated super solidus liquid phase sintered AISI type M3/2 high speed steel powder has been evaluated. Hardness measurements, Rockwell C indentation and scratch testing were used to evaluate the mechanical properties and light optical microscopy and scanning electron microscopy were used for post-test characterisation. The results show that it is possible to starch consolidate and sinter large particle size high speed steel powder to obtain microstructures with high mechanical strength. However, the results show a strong correlation between the as sintered microstructure and the resulting mechanical properties and illuminate the importance of having a dense and isotropic microstructure in order to meet engineering requirements in demanding applications. Consequently, the failure mechanisms observed during indentation and scratch testing can be related to residual pores, present in the low temperature sintered samples, and a coarse microstructure with eutectic carbides, present in the high temperature sintered samples. 

  • 23.
    Harlin, Peter
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Starch consolidation of M3/2 high speed steel - Influence of sintering temperature on mechanical properties2007In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 50, no 3, p. 232-238Article in journal (Refereed)
  • 24.
    Harlin, Peter
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Starch consolidation of M3/2 high speed steel powder: influence of process parameters on resulting microstructure2007In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 50, no 4, p. 345-353Article in journal (Refereed)
    Abstract [en]

    The possibility to produce near net shape high speed steel components with an adequate microstructure by the combination of starch consolidation (SC) and super solidus liquid phase sintering (SLPS) has been evaluated using a gas atomised M3/2 high speed steel (HSS) powder. Characterisation of the green body and as sintered microstructures using light optical microscopy (LOM), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX) reveals that both the SC and SLPS processes strongly influence the resulting microstructure and thus the properties of the high speed steel material. The results obtained show that the morphology and distribution of starch to a high extent affect the green body surface strength and that the large pores remaining after sintering originates from entrapped air introduced in the fabrication process of the green body. The results illuminate the possibility to combine SC and SLPS to produce HSS components with fully dense microstructures and retained green body geometry from a powder with particle size distribution 50 - 150 mu m.

  • 25.
    Hatami, Sepehr
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Lyckfeldt, Ola
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Tönnäng, Lenny
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Fransson, Karin
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF.
    Flow properties of tool steel powders for selective laser melting -  influence of thermal and mechanical powder treatments2017In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, p. 1-10Article in journal (Refereed)
    Abstract [en]

    In powder bed fusion additive processes the flow properties of the powder influence the quality of the final component and the efficiency of the process. In this investigation an attempt is made to identify flowability indicators which can describe the flow performance of the powder during the powder layering (i.e. recoating) step; common to all powder bed fusion processes. To this end, shear tests were performed by means of a powder rheometer. Bulk density, flow function and degree of cohesion were measured. The results suggest that there is a good correlation between the aforementioned parameters and the flowability of the powder during SLM processing. In addition, it was found that thermal treatments and tumbling enhance flowability. Thermal treatments were performed at 150, 200 and 250°C for a period of 10 €…min and in air.

  • 26.
    Hedberg, Yolanda
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Norell, Mats
    Materials and Manufacturing Technology, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
    Hedberg, Jonas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Szakálos, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Linhardt, Paul
    Institute for Chemical Technologies and Analytics (CTA), Vienna University of Technology, Getreidemarkt 9/164, A-1060 Vienna, Austria.
    Odnevall Wallinder, Inger
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Surface characterisation of fine inert-gas- and water-atomised stainless steel 316L powders - formation of thermodynamically unstable surface oxide phases2013In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 56, no 2, p. 158-163Article in journal (Refereed)
    Abstract [en]

    New insights are presented on the speciation of surface oxide phases on fine inert gas atomised (GA, <45 and <4 mu m) and water atomised (WA, <45 mu m) stainless steel AISI 316L powders. X-ray photoelectron and Auger electron spectroscopy, scanning electron microscopy, Raman spectroscopy, and cyclic voltammetry were applied for the characterisation. Oxidised manganese was strongly enriched in the outermost surface oxide of the GA powders (13 and 47 wt-%), an effect increasing with reduced particle size. Manganese and sulphur were enriched in oxide nanoparticles on the surface. Oxidised silicon (59 wt-%) was enriched on the WA powder surface. Tri-or tetravalent manganese oxides were observed on the GA particles in addition to alpha-Fe2O3, and Cr2O3. The oxide of the WA powder revealed in addition the likely presence of a silicate rich phase, mainly consisting of tetravalent Si, di- and/or trivalent Fe, and hexavalent Cr, which was confirmed not present as chromate.

  • 27.
    Hjortsberg, Erik
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Bergquist, Bjarne
    Department of Quality Technology, Luleå University of Technology, Luleå, Sweden.
    Filling induced density variations in metal powder2002In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 45, no 2, p. 146-153Article in journal (Refereed)
    Abstract [en]

    Filling induced density variations is a problem that has long been overlooked by powder metallurgy scientists. In this paper,densityvariations are addressed, both why they occur and what problems they may cause. A test method, including a test rig, is presented that is able to link several different factors to resulting powder densities. The relations are analysed and several density affecting mechanisms are suggested. These mechanisms could be used either to minimise density differences within parts or to control density by directing powder to critical areas.

  • 28.
    Häggblad, Hans-åke
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Oldenburg, Mats
    Numerical simulation of powder compaction for two multilevel ferrous parts, including powder characterisation and experimental validation2002In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 45, no 4, p. 335-344Article in journal (Refereed)
    Abstract [en]

    The paper presents a summary of two case studies that were carried out by the scientific team in the Thematic Network PM Modnet. During the life of this project, the compaction of complex multilevel ferrous components was investigated. These formed a vehicle to explore methods to characterise the yield and friction properties of the powder, perform simulation of the compression stage of the forming process, complete experimental trials, and compare experimental and simulated results. Density comparisons were made with results from Archimedes, quantitative metallography, and computerised tomography and force levels were compared with recordings from the pressing trials. The results highlight differences between equipment and experimental techniques used in characterising powders. They also show that hardness, metallographic analysis, and computerised tomography may be used to measure density variations throughout the compact. The prediction of density variation was reasonably consistent when using different simulations, whereas punch force prediction showed good consistency. It was found that predicted and measured density distributions agree within 0·05 to 0·5 g cm-3 and that punch force levels may be predicted within 10 to 30%. The study effectively establishes a benchmark with which to compare and improve future simulations.

  • 29.
    Khraisat, Walid
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Graphite pore filling and surface blistering of sintered Fe-C-Si2012In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 55, no 3, p. 242-247Article in journal (Refereed)
    Abstract [en]

    Different alloys of the system Fe-C-Si were sintered to obtain a grey iron microstructure and then hardened by post-sintering heat treatment to obtain a martensitic structure. The main problem in the development of this approach is related to the occurrence of surface blistering in the as sintered material when sintering in N2 atmosphere. Surface blistering is explained by the increase in entrapped gas pressure in pores caused by graphite pore filling. A mechanism has been proposed to explain graphite pore filling. According to this mechanism, graphite pore filling is caused by the C activity difference between the gas entrapped in pores and the matrix, which is a consequence of Boudouard’s reaction. This difference in C activity causes C to diffuse from the matrix to the pores, thus filling pores with graphite. © 2012 Institute of Materials, Minerals and Mining.

  • 30.
    Leisner, Peter
    et al.
    Jönköping University, School of Engineering, JTH, Computer and Electrical Engineering.
    Leu, R. Leu
    Møller, Patrick
    Electroplating of Porous Powder Metallugical Compacts1997In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 40, no 3, p. 207-210Article in journal (Refereed)
  • 31. Li, W.B.
    et al.
    Häggblad, Hans-åke
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Constitutive laws for hot isostatic pressing of powder compact1997In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 40, no 4, p. 279-281Article in journal (Refereed)
    Abstract [en]

    The present state of hipping modelling is briefly reviewed using the principles of densification theory and plastic deformation theory for porous materials on the basis of a macro- and microscopic approach. The features of these two approaches are discussed. The constitutive equation for a porous compact relating the strains and stresses (macroscopic approach) is modified by incorporating the rate equations for densification mechanisms (microscopic approach). A new modified constitutive equation is then derived which combines the advantages of both approaches. Based on this equation, the hipping process can be simulated. The density and shape change of a porous compact during densification or deformation processes under conditions of either isostatic or nonisostatic pressure can be predicted

  • 32.
    Li, Wei-Bin
    et al.
    Luleå tekniska universitet.
    Easterling, Kenneth E.
    Luleå tekniska universitet.
    Cause and effect of non-uniform densification during hot isostatic pressing1992In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 35, no 1, p. 47-52Article in journal (Refereed)
    Abstract [en]

    Hot isostatic pressing (hipping) is an extremely efficient way of densifying ceramic and high alloy metallic powders, or for healing porosity in castings. However, depending on the parameters of pressure, temperature, rate of heating, and sample size, hipping can result in a non-uniform mode of densification. This mainly occurs when a rapidly heated sample, or a sample of large dimensions, densifies quickly at the surface to produce, if effect, a fully dense, hard shell. It is shown that there can be a number of negative factors resulting from this, including reduced rates of densification, sample sample shape change, non-uniform shrinkage, and the development of residual stresses in the sample. Criteria for predicting whether or not non-uniform densification will occur are presented and evaluated. Steel and Cu are discussed.

  • 33.
    Luukkonen, Petri
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Hjortsberg, Erik
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Ericsson, Torsten
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Potential drop measurements of porosity in PM green bodies2003In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 46, no 4, p. 335-341Article in journal (Refereed)
    Abstract [en]

    The direct current potential drop method (DCPD) has been applied to four differently shaped green bodies made of iron based powders. The density and porosity has been measured in the bodies and correlated with potential drop. When the porosity is well known, a good correlation between potential drop and porosity is found. By comparison with literature it is concluded that the potential drop in green bodies varies more with porosity than in sintered bodies.

  • 34.
    Mellin, Pelle
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea KIMAB.
    Shvab, Ruslan
    Chalmers University of Technology, Sweden.
    Strondl, Annika
    RISE - Research Institutes of Sweden, Swerea, Swerea KIMAB.
    Randelius, Mats
    RISE - Research Institutes of Sweden, Swerea, Swerea KIMAB.
    Brodin, Håkan
    Siemens, Sweden.
    Hryha, Eduard
    Chalmers University of Technology, Sweden.
    Nyborg, Lars
    Chalmers University of Technology, Sweden.
    COPGLOW and XPS investigation of recycled metal powder for selective laser melting2017In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901Article in journal (Refereed)
    Abstract [en]

    The purpose of this paper is to compare, in terms of depth composition profile, a recycled hastelloy X powder and a virgin powder of the same alloy. We compare also the COPGLOW (compacted powder glow discharge analysis) method to the more established XPS (X-ray photoelectron spectroscopy) technique, in terms of similarity in reported elemental contents. A good match between the two methods was obtained on the surface of the powder particles (using an etching depth of 1 nm). Similar oxide layer thickness, of about 0.5–1 nm, was found on both powders by COPGLOW. Oxidation sensitive elements, such as Cr, were found on the surfaces by both XPS and COPGLOW on both powders. Surface content of Si appears to have decreased during use in selective laser melting. Finally, the two methods did not otherwise reveal any unexpected features in the depth profiles.

  • 35.
    Nabeel, Muhammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Frykholm, R.
    Hedström, Peter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Influence of alloying elements on Ni distribution in PM steels2014In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 57, no 2, p. 111-118Article in journal (Refereed)
    Abstract [en]

    Powder metallurgical (PM) steels with elemental Ni additions exhibit non-homogenous microstructures with soft Ni rich areas, lean in C, after conventional sintering. Though, the exact correlation between the distribution of Ni and mechanical properties is not well known and depends on the conditions, e.g. the load state, it is desirable to be able to control the distribution of Ni since it plays a major role in the properties of Ni PM components. By introducing other alloying elements, the microstructure homogeneity of Ni containing PM steels, can be influenced. Thus, the effect of common alloying elements on the homogeneity of sintered microstructures has been investigated in the present work. It is found that additions of either C or Mo have minor effect on Ni distribution in the Fe-Ni system. However, addition of both C and Mo to Fe-Ni improves the Ni distribution. In addition, a strong interaction between Ni and Cu is observed and it enhances the Ni homogeneity. Furthermore, the influence of Cu is more pronounced in presence of C.

  • 36.
    Persson, Fredrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Eliasson, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Prediction of particle size for water atomised metal powders: parameter study2012In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 55, no 1, p. 45-53Article in journal (Refereed)
    Abstract [en]

    This work aims to investigate how some significant atomising parameters influence the mass median particle size d50 of water atomised metal powders. More specifically, these were water pressure, melt flowrate, water jet angle, liquid metal viscosity and surface tension. Existing models for the prediction of d50 during water atomisation were reviewed. The selected models were fitted and compared with atomising experiments of liquid iron containing 0.5–4.4%C. Experimental results and model calculations were used in a parameter study to investigate how the different parameters influenced d50. The effect on d50 was large for the water pressure, medium for the viscosity and low for the melt flowrate and surface tension. Model calculations indicate that the jet angle has a large effect on d50, which should be verified by additional studies. The model proposed by Bergquist (B. Bergquist: Powder Metall., 1999, 42, 331–343) showed the best agreement with the current experimental data.

  • 37.
    Solimanjad, Naghi
    Luleå tekniska universitet.
    New method for measuring and characterisation of friction coefficient at wide range of densities in metal powder compaction2003In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 46, no 1, p. 49-54Article in journal (Refereed)
    Abstract [en]

    In order to investigate the friction behavior of powder during compaction, a new method has been developed. Compaction is a complicated process and direct and continuous measurement of the coefficient of friction is not easy, because the coefficient of friction varies due to changes in such process parameters as pressure distributions, powder surface deformation etc. In this paper, a new device for measuring the coefficient of friction between metal powder particles in contact with the die wall during compaction is presented. Using the conventional methods for direct measurement of the radial pressure during compaction is very difficult. The new device offers the possibility of investigating the normal pressure on the powder particles directly and continuously by keeping the green density constant. The measurements are performed using strain gauges mounted on the upper punch. The upper punch surface in the new device corresponds to the die wall in a conventional press. The sliding velocity, compaction velocity, normal load and temperature can be monitored and controlled. Measurement of the coefficient of friction at low densities is one of the advantages and possible applications of this apparatus. The investigation shows that the powder compaction is controlled by a combination of powder rearrangement and elastic and plastic deformation of particles. At densities below 4 g cm-3 the dominant process is particle rearrangement. No plastic deformation occurs at such low values of density. At densities above 4.5 g cm-3 the plastic deformation of the powder surface in contact with the die wall seems to be completed and the coefficient of friction is more or less constant

  • 38.
    Staf, Hjalmar
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.). AB Sandvik Coromant, R&D, Stockholm, Sweden.;Royal Inst Technol, Dept Solid Mech, SE-10044 Stockholm, Sweden..
    Nyrot, Elias Forssbeck
    AB Sandvik Coromant, R&D, Stockholm, Sweden..
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.). Royal Inst Technol, Dept Solid Mech, SE-10044 Stockholm, Sweden..
    On the usage of a neutron source to determine the density distribution in compacted cemented carbide powder compounds2018In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 61, no 5, p. 389-394Article in journal (Refereed)
    Abstract [en]

    Density variations in pressed powder materials are of substantial importance and will affect shrinkage and geometry after sintering. It is therefore important to accurately measure this quantity in green bodies. This is emphasised by the fact that the density variation can be used for determining material properties in constitutive mechanical models of compaction. An obvious method to determine the density variation is X-ray tomography. For cemented carbides this is not a possible alternative due to the very high X-ray absorption of tungsten making the samples impossible to penetrate. Neutron radiation has a much higher penetration and this suggests that a neutron source could be used for density distribution determination in such materials. This was investigated currently showing promising results when compared with finite element predictions. It is clear that this approach must be improved to be able to use neutron radiation as a tool for density determination. Improvements are suggested.

  • 39.
    Staf, Hjalmar
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Olsson, Erik
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Lindskog, P.
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    On rate-dependence of hardmetal powder pressing of cutting inserts2017In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 60, no 1, p. 7-14Article in journal (Refereed)
    Abstract [en]

    The rate-dependence of hardmetal powder pressing in cutting insert production is investigated experimentally and numerically. In the latter case, the finite element method is relied upon using a continuum mechanics approach. In particular, possible rate-dependency due to creep deformation and rate-dependent friction is discussed with the experimental investigation focusing mainly on dimensional changes during sintering but also pressing forces. The results indicate that rate-dependent frictional effects are the dominating feature and accordingly, it can be argued that for the metal powders investigated here, creep deformations do not have to be accounted for in the constitutive description at the timescales relevant for powder pressing and when the shape after sintering is concerned. For the present powder, the apparent frictional effect decreases at higher pressing rates. Additional details of the friction behavior are studied comparing finite element simulations with experiments.

  • 40.
    Tahir, Abdul Malik
    et al.
    KTH.
    Amberg, Gustav
    KTH.
    Hedström, Peter
    KTH.
    Bergman, O.
    Höganäs AB.
    Chasoglou, D.
    Swerea KIMAB AB.
    Frisk, K.
    Swerea KIMAB AB.
    Behaviour of master alloy during sintering of PM steels: redistribution and dimensional variations2015In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 58, no 2, p. 133-141Article in journal (Refereed)
    Abstract [en]

    The addition of alloying elements in low alloyed PM steels in the form of a master alloy gives the advantage of introducing oxidation sensitive but less expensive elements and also allows manipulation in composition adjustment to achieve desired properties. In this work, interrupted sintering trials of the Fe-2MA-0.5C (%) (MA = Cu based master alloy) are performed. The behaviour of the liquid forming master alloy, for instance in terms of liquid phase formation, alloying element redistribution and effect on the dimensional changes, is investigated. The results show that master alloy particles melt over a range of temperature, which is also supported by the thermodynamic calculations. The low swelling in the master alloy system, compared to a reference system of Fe-2Cu-0.5C, is attributed to the progressive melting of the master alloy. The mean diffusion distance of Cu in Fe at the interparticle boundaries is 5.8 mu m after 34 min of isothermal holding.

  • 41.
    Tahir, Abdul Malik
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Physicochemical Fluid Mechanics.
    Amberg, Gustav
    KTH, School of Engineering Sciences (SCI), Mechanics, Physicochemical Fluid Mechanics.
    Hedström, Peter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Bergman, O.
    Chasoglou, D.
    Frisk, K.
    Behaviour of master alloy during sintering of PM steels: redistribution and dimensional variations2015In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 58, no 2, p. 133-141Article in journal (Refereed)
    Abstract [en]

    The addition of alloying elements in low alloyed PM steels in the form of a master alloy gives the advantage of introducing oxidation sensitive but less expensive elements and also allows manipulation in composition adjustment to achieve desired properties. In this work, interrupted sintering trials of the Fe-2MA-0.5C (%) (MA = Cu based master alloy) are performed. The behaviour of the liquid forming master alloy, for instance in terms of liquid phase formation, alloying element redistribution and effect on the dimensional changes, is investigated. The results show that master alloy particles melt over a range of temperature, which is also supported by the thermodynamic calculations. The low swelling in the master alloy system, compared to a reference system of Fe-2Cu-0.5C, is attributed to the progressive melting of the master alloy. The mean diffusion distance of Cu in Fe at the interparticle boundaries is 5.8 mu m after 34 min of isothermal holding.

  • 42.
    Tahir, Abdul Malik
    et al.
    KTH Royal Institute of Technology, Sweden.
    Amberg, Gustav
    KTH Royal Institute of Technology, Sweden.
    Hedström, Peter
    KTH Royal Institute of Technology, Sweden.
    Bergman, Ola
    Höganäs AB, Sweden.
    Chasoglou, Dimitris
    RISE - Research Institutes of Sweden, Materials and Production, KIMAB.
    Frisk, Karin
    RISE - Research Institutes of Sweden, Materials and Production, KIMAB.
    Behaviour of master alloy during sintering of PM steels: Redistribution and dimensional variations2015In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 58, no 2, p. 133-141Article in journal (Refereed)
    Abstract [en]

    The addition of alloying elements in low alloyed PM steels in the form of a master alloy gives the advantage of introducing oxidation sensitive but less expensive elements and also allows manipulation in composition adjustment to achieve desired properties. In this work, interrupted sintering trials of the Fe-2MA-0.5C (%) (MA=Cu based master alloy) are performed. The behaviour of the liquid forming master alloy, for instance in terms of liquid phase formation, alloying element redistribution and effect on the dimensional changes, is investigated. The results show that master alloy particles melt over a range of temperature, which is also supported by the thermodynamic calculations. The low swelling in the master alloy system, compared to a reference system of Fe-2Cu-0.5C, is attributed to the progressive melting of the master alloy. The mean diffusion distance of Cu in Fe at the interparticle boundaries is 5.8 μm after 34 min of isothermal holding.

  • 43.
    Tahir, Abdul Malik
    et al.
    KTH.
    Amberg, Gustav
    KTH.
    Hedström, Peter
    KTH.
    Bergman, Ola
    Höganäs AB.
    Frisk, Karin
    Swerea KIMAB AB.
    Cu redistribution during sintering of Fe–2Cu and Fe–2Cu–0·5C compacts2014In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 57, no 5, p. 373-379Article in journal (Refereed)
    Abstract [en]

    The effective use of alloying elements in powder metallurgical steels requires a deep understanding of their redistribution kinetics during sintering. In this work, interrupted sintering trials of Fe–2Cu and Fe–2Cu–0·5C compacts were performed. Moreover, diffusion simulations of Cu in γ-Fe using Dictra were performed. It is found that transient liquid phase penetrates the Fe interparticle and grain boundaries in less than 3 min of holding time. However, C addition limits the penetration of liquid Cu, particularly into grain boundaries of large Fe particles. The results also show that the mean diffusion distance of Cu in γ-Fe in the C added system is slightly lower than that in the C-free system at 3 min of holding time; however, after 33 min, the mean diffusion distance is similar in both systems. The diffusion distances of Cu in γ-Fe, predicted by Dictra, are in good agreement with the measured values.

  • 44.
    Tahir, Abdul Malik
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Physicochemical Fluid Mechanics.
    Amberg, Gustav
    KTH, School of Engineering Sciences (SCI), Mechanics, Physicochemical Fluid Mechanics.
    Hedström, Peter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Bergman, Ola
    Frisk, Karin
    Cu redistribution during sintering of Fe–2Cu and Fe–2Cu–0·5C compacts2014In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 57, no 5, p. 373-379Article in journal (Refereed)
    Abstract [en]

    The effective use of alloying elements in powder metallurgical steels requires a deep understanding of their redistribution kinetics during sintering. In this work, interrupted sintering trials of Fe–2Cu and Fe–2Cu–0·5C compacts were performed. Moreover, diffusion simulations of Cu in γ-Fe using Dictra were performed. It is found that transient liquid phase penetrates the Fe interparticle and grain boundaries in less than 3 min of holding time. However, C addition limits the penetration of liquid Cu, particularly into grain boundaries of large Fe particles. The results also show that the mean diffusion distance of Cu in γ-Fe in the C added system is slightly lower than that in the C-free system at 3 min of holding time; however, after 33 min, the mean diffusion distance is similar in both systems. The diffusion distances of Cu in γ-Fe, predicted by Dictra, are in good agreement with the measured values.

  • 45.
    Tahir, A.M.
    et al.
    KTH Royal Institute of Technology.
    Amberg, G.
    KTH Royal Institute of Technology.
    Hedström, P.
    KTH Royal Institute of Technology.
    Bergman, O.
    Höganäs AB.
    Frisk, Karin
    RISE, Swerea, Swerea KIMAB.
    Cu redistribution during sintering of Fe-2Cu and Fe-2Cu-0·5C compacts2014In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 57, no 5, p. 373-379Article in journal (Refereed)
    Abstract [en]

    The effective use of alloying elements in powder metallurgical steels requires a deep understanding of their redistribution kinetics during sintering. In this work, interrupted sintering trials of Fe-2Cu and Fe-2Cu-0·5C compacts were performed. Moreover, diffusion simulations of Cu in c-Fe using Dictra were performed. It is found that transient liquid phase penetrates the Fe interparticle and grain boundaries in less than 3 min of holding time. However, C addition limits the penetration of liquid Cu, particularly into grain boundaries of large Fe particles. The results also show that the mean diffusion distance of Cu in c-Fe in the C added system is slightly lower than that in the C-free system at 3 min of holding time; however, after 33 min, the mean diffusion distance is similar in both systems. The diffusion distances of Cu in c-Fe, predicted by Dictra, are in good agreement with the measured values. © 2014 Institute of Materials, Minerals and Mining.

  • 46. Uhrenius, B.
    et al.
    Bergstrom, L.
    Ågren, John
    KTH, Superseded Departments, Metallurgy.
    Westin, G.
    Nygren, M.
    Salwen, A.
    Inorganic interfacial engineering: processing of hard materials2004In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 47, no 4, p. 317-331Article in journal (Refereed)
    Abstract [en]

    Inorganic interfacial engineering may be regarded as the core of powder metallurgical processing of hard materials. The present paper reviews recent results from an interdisciplinary research effort, BRIIE ( the Brinell Centre for Inorganic Interfacial Engineering), a joint effort between five industrial companies, three universities, two research institutes and VINNOVA ( the Swedish Agency for Innovation Systems). The research involves experimental work on the aqueous processing of powders and the use of surface actants is reviewed as well as the colloidal processing of ceramics. Pressing and sintering of agglomerated powders have been studied both theoretically and experimentally. Models for the simulation of pressing and sintering of hard metal powders are developed. Results on ceramic materials obtained by spark plasma sintering and their resistance to thermal shock are reported.

  • 47. Wikman, Bengt
    et al.
    Solimannezhad, N.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Oldenburg, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Häggblad, Hans-åke
    Wall friction coefficient estimation through modelling of powder die pressing experiment2000In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 43, no 2, p. 132-138Article in journal (Refereed)
    Abstract [en]

    Forming of PM components through powder pressing is a process, which is influenced by the friction between the powder and the tool walls. For good performance of the pressing process it is of great interest to understand and estimate the effects of powder-wall friction. However, quantification of the friction coefficient between the powder and the tool is a delicate task. Local contact conditions, such as contact stress, must be measured or otherwise estimated in order to evaluate the coefficient of friction. Here, the friction coefficient is estimated by combining an experiment with modelling of the experiment. Two methods for assessment of friction are presented, an optimization approach using finite element analyses and an analytical approach. Experimental data are taken from the single action cold pressing of a cylinder shaped component.

  • 48.
    Yang, Jie
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Univ Politecn Cataluna, Spain; AMES Sintered Met Components, Spain.
    Roa, J. J.
    Univ Politecn Cataluna, Spain; Univ Politecn Cataluna, Spain.
    Schwind, M.
    SECO Tools AB, Sweden.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Johansson-Jöesaar, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Esteve, J.
    Univ Barcelona, Spain.
    Llanes, L.
    Univ Politecn Cataluna, Spain; Univ Politecn Cataluna, Spain.
    Implementation of advanced characterisation techniques for assessment of grinding effects on the surface integrity of WC-Co cemented carbides2018In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 61, no 2, p. 100-105Article in journal (Refereed)
    Abstract [en]

    Grinding is a key step on the manufacturing process of WC-Co cemented carbides (hardmetals). In this work, an investigation of grinding effects on the surface integrity of hardmetals is conducted. It is done by combining diverse advanced characterisation techniques: X-ray diffraction, field emission-scanning electron microscopy, electron back scatter diffraction, focused ion beam - 3D tomography and transmission electron microscopy. The study is carried out in a fine-grained WC-Co grade. Besides ground state, polished surface finish condition is assessed for comparison purposes. It is evidenced that grinding induces significant alterations: 3D tomography illustrates microcracking exists down to 2.5 mu m depth with a highly anisotropic distribution at the subsurface, large compressive residual stresses extending until subsurface levels of about 12 mu m, and phase transformation of binder from the original fcc phase into the hcp one, as well as severe plastic deformation observed within the binder at the surface level.

  • 49.
    Zhang, Zongyin
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Frisk, K.
    Salwen, A.
    Sandström, Rolf
    KTH, Superseded Departments, Materials Science and Engineering.
    Mechanical properties of Fe-Mo-Mn-Si-C sintered steels2004In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 47, no 3, p. 239-246Article in journal (Refereed)
    Abstract [en]

    Four Fe-Mn-Si master alloy powders with the compositions Fe-35%Mn-14%Si, Fe-35%Mn-20%Si, Fe-45%Mn-20%Si and Fe-60%Mn-14%Si were made by the cast milling method, and used to produce Fe-Mo-Mn-Si-C sintered steels. The effects of master alloy composition and sintering atmosphere on the mechanical properties and dimensional change of the sintered steels were studied. The steels were sintered either at 1250 degreesC for 30 min in hydrogen-30% nitrogen or at 1120 degreesC for 30 min in hydrogen and nitrogen-10% hydrogen with different dewpoints. After transient liquid phase sintering, the ultimate tensile strength, yield strength and hardness increase and elongation decreases with increasing contents of manganese and carbon. The dewpoint of sintering atmospheres had little effect on the properties, probably as the addition of manganese and silicon was in the form of a master alloy. The highest tensile strength and smallest dimensional change were obtained in a steel with a composition of Fe-0.85%Mo-1.40% Mn-0-8%Si-0.7%C.

1 - 49 of 49
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