Microstructure and Properties of SKD61 Die Steel Strengthened by Biomimetic Laser-Remelting

In order to improve the surface hardness and anti-fatigue properties, the SKD61 die steel was strengthened by laser-remelting. The microstructure and chemical composition distribution of SKD61 steel after laser-remelting were observed and analyzed by optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDS). The hardness of laser melted zone and the service life of the processed die-casting die were also tested. The results show that SKD61 steel had three layer structures, including the melting zone, heat affected zone and base metal. The microstructure of melted zone was very fine equiaxial crystal and columnar crystal, and the impurity phase was eliminated. The alloying elements distributed uniformly after laser-remelting process. Compared with conventional heat treatment, the microhardness of melted zone increased significantly. The service life of SKD61 steel top cover die-casting die had more than doubled after laser-remelting.