Structure and Properties of Plasma Phase Transformation Strengthening Layer of W18Cr4V

W18Cr4V high-speed steel was strengthened by compressed arc plasma, the microstructure and microhardness were investigated. The results showed that strengthening layer was consisted of mixed lathy and acicular martensites, a small amount retained austenite and carbides, and there was a relationship of α-Fe[111]∥γ-Fe[110], carbides referred to M_6C、M_(23)C_6、MC、M_2C etc. The structure of the strengthening layer was obviously refined, and the grade of grain size increased from 7~8 to 11~12 after plasma strengthening. The microhardness of strengthening layer showed a nonlinear relationship with the depth, and the maximum microhardness was 1000HV_(0.1).The depth of strengthening layer was increased with increasing working electric current, but the microhardness of the top surface was decreased.