Influence of Preheating Temperature on Microstructure Evolution and Hardness of High‐Speed Steel AISI M50 Processed by Laser Powder Bed Fusion

steel research international, vol. 94

Abstract

The laser powder bed fusion (LPBF) technology has been involved in the tooling industry to produce tools with complex geometry and integrated functions. However, tool steels with high carbon content tend to crack due to the thermal stresses during the LPBF process. One solution is increasing the powder bed temperature to avoid large thermal gradients. In the present study, the influence of the preheating temperature on microstructure and corresponding hardness is systematically investigated. With the help of time–temperature–transformation diagram, the phase evolution during the LPBF process is systematically explained. AISI M50 samples are produced by LPBF from room temperature to a preheating temperature of 650 °C. Higher preheating temperatures shift the optimal laser parameter window to lower volume energy densities. A cellular/dendritic microstructure formed during the rapid solidification with retained austenite is located at the interdendritic regions. Moreover, a high preheating temperature reduces the retained austenite fraction, specifically from 39% without preheating to 7.6% at 650 °C preheating temperature.

Authors 7

1. Siyuan Qin corresponding Aachen chair Institute for Materials Applications in Mechanical Engineering

   RWTH Aachen University

   Affiliation as printed

   Chair and Institute for Materials Applications in Mechanical Engineering RWTH Aachen University (IWM) 52064 Aachen Germany

   Chair and Institute for Materials Applications in Mechanical Engineering, RWTH Aachen University (IWM), 52064 Aachen, Germany

2. Jasmin Saewe Aachen Laser Technology Fraunhofer Institute for Laser Technology (ILT)

   Fraunhofer Institute for Laser Technology

   Affiliation as printed

   Laser Technology Fraunhofer Institute for Laser Technology (ILT) 52074 Aachen Germany

   Laser Technology, Fraunhofer Institute for Laser Technology (ILT), 52074 Aachen, Germany

3. Johannes Kunz Aachen Institute of Applied Powder Metallurgy and Ceramics

   RWTH Aachen University

   Affiliation as printed

   Institute of Applied Powder Metallurgy and Ceramics RWTH Aachen University e.V. (IAPK) 52064 Aachen Germany

   Institute of Applied Powder Metallurgy and Ceramics, RWTH Aachen University e.V. (IAPK), 52064 Aachen, Germany

4. Simone Herzog Aachen chair Institute for Materials Applications in Mechanical Engineering

   RWTH Aachen University

   Affiliation as printed

   Chair and Institute for Materials Applications in Mechanical Engineering RWTH Aachen University (IWM) 52064 Aachen Germany

   Chair and Institute for Materials Applications in Mechanical Engineering, RWTH Aachen University (IWM), 52064 Aachen, Germany

5. Anke Kaletsch Aachen chair Institute for Materials Applications in Mechanical Engineering Institute of Applied Powder Metallurgy and Ceramics

   RWTH Aachen University

   Affiliation as printed

   Chair and Institute for Materials Applications in Mechanical Engineering RWTH Aachen University (IWM) 52064 Aachen Germany

   Institute of Applied Powder Metallurgy and Ceramics RWTH Aachen University e.V. (IAPK) 52064 Aachen Germany

   Chair and Institute for Materials Applications in Mechanical Engineering, RWTH Aachen University (IWM), 52064 Aachen, Germany

   Institute of Applied Powder Metallurgy and Ceramics, RWTH Aachen University e.V. (IAPK), 52064 Aachen, Germany

6. Johannes Henrich Schleifenbaum Aachen Digital Additive Production (DAP)

   RWTH Aachen University

   Affiliation as printed

   Digital Additive Production RWTH Aachen University (DAP) 52074 Aachen Germany

   Digital Additive Production, RWTH Aachen University (DAP), 52074 Aachen, Germany

7. Christoph Broeckmann Aachen chair Institute for Materials Applications in Mechanical Engineering Institute of Applied Powder Metallurgy and Ceramics

   RWTH Aachen University

   Affiliation as printed

   Chair and Institute for Materials Applications in Mechanical Engineering RWTH Aachen University (IWM) 52064 Aachen Germany

   Institute of Applied Powder Metallurgy and Ceramics RWTH Aachen University e.V. (IAPK) 52064 Aachen Germany

   Chair and Institute for Materials Applications in Mechanical Engineering, RWTH Aachen University (IWM), 52064 Aachen, Germany

   Institute of Applied Powder Metallurgy and Ceramics, RWTH Aachen University e.V. (IAPK), 52064 Aachen, Germany