Influence of powder nitriding on the mechanical behavior of laser-powder bed fusion processed tool steel X30CrMo7-2

Stern, F. and Grabienski, F. and Walther, F. and Boes, J. and Röttger, A. and Theisen, W.

Volume: 62 Pages: 19-26
DOI: 10.3139/120.111446
Published: 2020

Additive manufacturing allows for the production of highly complex structures due to its layer-wise local melting of powder material. For this reason, this technique has a high potential for manufacturing extremely lightweight components potential. However, laser based additive manufacturing is still restricted due to the limited amount of processable alloys, especially Fe-based materials. A main object in current research is to expand the varieties for steel that may be used. Additionally, the modification and optimization of steel powder is seen as an interesting aspect for improving the material properties of additively manufactured parts. In this work, secondary hardenable martensitic tool steel X30CrMo7-2 is investigated, starting from the raw powder which is enriched with nitrogen by gas nitriding and subsequently characterized to ensure the usability of the modified powder for laser-powder bed fusion. In a next step, the raw and nitrided powder are used to generate cylindrical specimens to allow for further analysis of the microstructure and for a mechanical characterization of compression behavior. Moreover, a variety of heat treatments is carried out. The higher content of nitrogen leads to an increase in porosity. However, the addition of nitrogen causes an increase in hardness and in the compressive yield point, especially after heat treatment. After tempering, compressive yield stress is increased from 1,111 MPa to 1990 MPa, while for conventional material it is slightly reduced from 1,316 MPa to 1225 MPa. © Carl Hanser Verlag GmbH & Co. KG

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