Microstructural evolution and tribological properties of M2 high-speed steel fabricated under various selective electron beam melting processing parameters

Abstract

In the current study, crack-free M2 high-speed steel (HSS) was produced by selective electron beam melting (SEBM) under different volumetric energy densities (VED, 40–56.3 J mm−3) and high powder bed preheating temperatures (PBPT, 750 °C and 820 °C). Results show that fully dense M2 HSS can be achieved under the VED of 43.6–47.9 J mm−3 and PBPT of 820 °C. Moreover, SEBM M2 HSS mainly consists of less than 7 µm α-Fe matrix grain as well as fine carbide, which were induced by high cooling rate of the molten pool. The fully dense sample presents ultra-high hardness (∼70 HRC) and excellent tribological properties. Its wear rate is 13.7 % lower than that of quenched and tempered wrought bulk counterpart.