Effects of Heat-treatment Process on Microstructure and Surface Oxide of GI Coating on Hot Stamped Steel

Effects of heat-treatment process on phase structure of GI coating on hot stamped steel were studied by FE-SEM and EDS. The phase of coating surface after heating was analyzed by element distribution and XRD. The results showed that the coating consists of oxide layer, Γ phase and α-Fe(Zn) after heated at high temperature. With the increase of the heating temperature and holding time, zinc oxides were formed and became a continuous zinc oxide layer in the last. With the increase of heating temperature and holding time, the coating surface oxides gradually increased, but the continuous alumina layer disappeared and Γ phase gradually reduced.