Feasability Investigation for Laser Powder Bed Fusion of High-Speed Steel AISI M50 with Base Preheating System

Laser Powder Bed Fusion (LPBF) is an additive manufacturing process employed in the aerospace, automotive, and medical industries. In these sectors, nickel-, aluminium-, and titanium-based alloys are mainly used for various applications. Yet, only few of the commonly used steels have been qualified for the LPBF process in the mechanical engineering industry, which normally uses hot work tool steels with less than 0.5 wt.-% carbon content. However, many applications need high wear-resistant steel alloys with high hardness, both of which can be achieved with a higher carbon content, like in high-speed steels. But when processed with LPBF, these steels often form cracks, making the process very challenging. In this feasibility investigation, we demonstrate that LPBF can be used to manufacture dense and crack-free specimens with a hardness of over 62 HRC (as built) from high-speed steel AISI M50 (carbon content of 0.8 wt.-%). Furthermore, we evaluate the influence of typical LPBF process parameters, especially of preheating temperatures up to 500 ℃, on the microstructure of the specimens.