Study on overlapping process in laser transformation hardening of stamping die

Microhardness, surface roughness and phase transformation of overlapping zone in multi-track laser hardening on a ductile cast iron QT700-2 were tested. The experimental results show that with proper processing parameters, the microhardness of treated layer can be higher than 50HRC. The temper softening in overlapping zone can be prevented by changing the overlapping ratio. The interlaced distribution of martensite and non-uniform, multi-scale structure in hardened zone after multi-track laser hardening led to a good wear and fatigue resistance of surface. Processing parameters of laser hardening on ductile cast iron were optimized.