Effect of strip entry temperature on the formation of interfacial layer during hot-dip galvanizing of press-hardened steel

Strip entry temperature is one of the important factors that affect alloying reactions at the steel/coating interface. This study focuses on the influence of strip entry temperature on phase formation at the press-hardened steel (PH) substrate/coating interface in zinc baths with 0.12 wt.% and 0.2 wt.% Al content respectively. The microstructure of the interfacial layer was characterized by Scanning Electron Microscope (SEM) and Glow Discharge Optical Emission Spectrometer (GDOES). It was determined that the microstructure components of steel/coating interface are significantly influenced by the strip entry temperature within 440-480 °C. In the zinc bath with 0.12 wt.% Al, the interfacial layer consists of mainly ζ phase (FeZn13), and the size of the ζ phase increases with the strip temperature. However, the amount of ζ phases and the Al content of the interfacial layer decreases with the strip temperature. Meanwhile, in the zinc bath with 0.2 wt.% Al, a continuous inhibition layer Fe2Al5 was formed on the steel surface. The Al enrichment at the interfacial layer increased with increasing strip temperature, accompanied with which is the coarser inhibition layer morphology.