Laser additive manufacturing of M2 high-speed steel

M2 high-speed steel samples were fabricated by laser additive manufacturing and tempered at different times at a temperature of 560 degrees C. The microstructures of deposited samples were characterised by fine equiaxial grains, dendrites and inter-dendritic network-shape eutectic carbides and were composed of supersaturated martensite, retained austenite and M-2 C-type carbides. The content of retained austenite gradually decreased with increasing tempering times. Meanwhile, the micro-hardness of deposited samples was 688 +/- 10 HV, while the first, second and third tempering times were 833 +/- 13 Hv, 710 +/- 6 Hv and 740 +/- 7 Hv, respectively (standard deviations). Wear resistances of all samples showed an adhesive wear mechanism, and M2 HSS without tempering had a lower friction coefficient with an average of 0.52. M2 HSS after tempering twice at 560 degrees C/2 h had a larger wear volume loss than others.