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Experimental and Theoretical Investigation of Selective Laser Melted Uddeholm Dievar ®
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
2019 (English)Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
Abstract [en]

The main problem encountered in this thesis is the lack of research and knowledge of selective laser melted-printing with Uddeholm Dievar®. This absence of information could cause issues regarding quality and properties of the alloy as well as uncertainty regarding an appropriate heat treatment cycle.

This thesis mainly focuses on observing the changes that occur in the microstructure when Uddeholm Dievar® is manufactured through the additive manufacturing (AM) method known as selective laser melting (SLM). The SLM- method consists of a high-power laser that melts together thin layers of powder, one layer at a time, until a three-dimensional product is created according to selected drawings.

The methodology on which this thesis is based on is the execution of a theoretical study, scientific experiments and thermodynamic calculations. Analysis of the microstructure is performed using a scanning electron microscope with techniques such as Energy-dispersive X-ray spectroscopy (EDS) and Electron backscatter diffraction (EBSD). The purpose of the methods are to map the constituent elements of the alloy and observe the orientation of the crystallographic phases in the atomic lattice respectively.

The results show that the powder, both before and after printing, mainly consists of martensite with a low amount of residual austenite. The amount of primary carbides is relatively low and has been classified as MC (V-rich) and/or M6C (Mo- rich) type. The remaining residual austenite could be explained by the segregation of constituent alloying elements, where the carbon content is a dominant factor to why the MS -temperature lowers significantly causing the presence of retained austenite even though SLM has a cooling rate that varies between 103 and 108 [K/s].

Abstract [sv]

Det huvudsakliga problemet som denna avhandling behandlar är bristen på forskning och kunskap inom selective laser melting (SLM) 3D-printing med Uddeholm Dievar®. Avsaknaden kan leda till sämre kvalité och produktegenskaper hos legeringen. Det kan även leda till ovisshet gällande val av lämplig värmebehandling.

Arbetet fokuserar på att dokumentera utformningen av stålets mikrostruktur när Uddeholm Dievar® tillverkas med den additiva tillverkningsmetoden SLM. Tillverkningsprocessen består av en högeffektslaser som detaljerat smälter samman tunna lager pulver, ett lager i taget, tills att en tredimensionell produkt skapats utefter valda ritningar.

Använda metoder är; utförandet av en teoretisk studie, vetenskapliga experiment och thermodynamiska beräkningar. Analys av mikrostrukturen genomförs med hjälp av svepelektronmikroskåp där teknikerna Energy-dispersive X-ray spectroscopy (EDS) och Electron backscatter diffraction (EBSD) används. Syftet med EDS är att kartlägga de ingående elementen i legeringen, syftet med EBSD är att se orientering av de kristallografiska faserna i atomgittret.

Resultaten visar på att legeringen, både före och efter printing, till största del består av martensit med en låg mängd restaustenit. Mängden primärkarbider är relativt låg och har klassifiserats som typen MC (V-rik) och/eller M6C (Mo- rik). Den kvarstående restausteniten kan möjligen förklaras av segringen av ingående legeringsämnen där kolhalten är en dominerande faktor som sänker MS-temperaturen. Detta gör att restaustenit förekommer trots den höga kylhastigheten som varierar mellan 103 och 108 [K/s] i SLM.

Place, publisher, year, edition, pages
2019. , p. 47
Series
TRITA-ITM-EX ; 2019:521
Keywords [en]
Uddeholm Dievar®, Additive manufacturing, AM, Selective laser melting, SLM, Gas-atomization, Hot-work tool steel
Keywords [sv]
Uddeholm Dievar®, Additiv tillverkning, AM, Selective laser melting, SLM, Gas- atomisering, Varmarbetsverktygsstål
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-254247OAI: oai:DiVA.org:kth-254247DiVA, id: diva2:1329763
Educational program
Master of Science in Engineering - Materials Design and Engineering
Supervisors
Examiners
Available from: 2019-07-09 Created: 2019-06-24 Last updated: 2019-07-09Bibliographically approved

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