A modified M2 high-speed steel enhanced by in-situ synthesized core-shell MC carbides

With high-energy wet ball milling M2 high-speed steel (HSS) powder and ferrovanadium alloy, an in-situ synthesized core-shell MC carbides reinforced M2 HSS was prepared via vacuum sintering. The phase, morphology and composition distribution of the milled composite powders, and the evolution of the sintered microstructure with the temperature and the associated mechanical properties before and after heat treatment were investigated. The ground powders were fully refined into lamellae and aggregates with V-element evenly distributed inside. Almost full densification (similar to 99.2% relative density) of the modified M2 steel was achieved at 1180 degree celsius by supersolidus liquid phase sintering. Near-spherical MC carbides and irregular M6C carbides were dispersed within the HSS matrix, and the MC developed a core-shell structure due to the solidification of the sintering liquid. Both the matrix grains and carbides of the sintered alloy had been refined by heat treatment, reaching satisfactory bending strength of 3580 MPa and hardness of HRC58, and enhancing the scratch resistance significantly.