The effect of diffusion treatment on the mechanical properties of hot-dip aluminum coating on AISI P20 steel

AISI P20 steel was coated by dipping it into a molten Al-7Si (wt.%) bath at 700 °C for 2 minutes. The aluminized steel specimens were subjected to diffusion treatment at 750 °C for 1-49 h. The mechanical properties of aluminized steel were tested with tensile and impact tests. The microstructure and elemental compositions (at.%) of intermetallic compounds formed in the aluminide layer were examined via SEM and EDS. Many pores were generated by phase transformation of τ5-Fe2Al8Si to form the Fe3(Al,Si)5 phase as well as the transformation of Fe3(Al,Si)5 to form FeAl islands in the outer aluminide layer after diffusion treatment. This formed a stress concentration in the aluminide layer. Therefore, the mechanical properties of aluminized AISI P20 steel decreased with time and temperature.