Modification of AISI M2 high-speed tool steels after laser-surface melting under different operating conditions

We applied a laser-surface melting treatment to AISI M2 high-speed steel – hardened and tempered – and studied the resulting surface characteristics (microstructure) and mechanical behaviour (hardness and wear performance). The steel was treated using a Nd:YAG continuous-wave laser with different operation conditions. The influence of the laser processing parameters on the individual beads and on the characteristics of the molten surface layer obtained using the multipass system with 50% overlap was studied. The microstructure characterization for all conditions is formed of MC- and M2C-type carbides, martensite, and retained austenite; the quantities of this phase depend on the operating conditions. It has been determined that low levels of power density and high scanning speeds of the beam lead to greater homogeneity in the microstructure with high hardness values and wear resistance.