Microstructural evolution of Al-Si coating and its influence on high temperature tribological behavior of ultra-high strength steel against H13 steel

Al-Si coated ultra-high strength steel (UHSS) has been commonly applied in hot stamping process. The influence of austenitizing temperature on microstructure of Al-Si coating of UHSS during hot stamping process and its tribological behavior against H13 steel under elevated temperature were simulatively investigated. The austenitizing temperature of Al-Si coated UHSS and its microstructual evolution were confirmed and analyzed by differential scanning calorimetry and scanning electron microscopy. A novel approach to tribological testing by replicating hot stamping process temperature history was presented. Results show that the hard and stable phases Fe2Al5 + FeAl2 formed on Al-Si coating surface after exposure to 930 °C for 5 min, which was found to be correlated to the tribological behavior of coating. The friction coefficient of coated steel was more stable and higher than that of uncoated one. The main wear mechanism of Al-Si coated UHSS was adhesion wear, while abrasive wear was dominant for the uncoated UHSS.