Laser surface hardening of H13 steel in the melt case

Laser heating caused a melting layer to form on the H13 steel, which usually has bad thermal conductivity and diffusivity. Therefore, the modified Ashby-Eastering heat-transfer equation was used to provide the temperature field for laser surface hardening in the melt. When the laser hardened H13 steel through surface melting, the basic microstructure of the dendrites was surrounded by an extremely fine lamellar structure in the melt layer. It is clear that the contours of the melting point isotherms and the critical phase transition temperature of H13 in the quenched and as-received conditions were comparable in the temperature distribution field under different laser energy densities. When the laser moves on, the phase transition temperature of H13 is raised and it becomes higher than the A1 temperature because the heating rate during laser processing is usually >104 °C/s. The larger the grain size or the more heterogeneous the structure, the higher the temperature and the longer the duration required for transforming the steel into austenite.