Formation of Kirkendall Pores in Aluminized Steel Sheets and Effect of Si in Aluminizing Bath

Aluminized steel sheets are highly resistant to elevated temperature. When they are heated for several hours above 800°C, part of the coating layer may delaminate owing to the presence of continuous Kirkendall pores, which are formed between the bcc_A2 and bcc_B2 phases because of the differences in the diffusion coefficients of Al and Fe in each phase. In this study, a numerical simulation was performed to predict the occurrence of Kirkendall pores, and the simulation results were compared with experimental results. The Si in the aluminizing bath significantly increased the number of Kirkendall pores owing to its effect on the ratio of the intrinsic diffusion coefficients (DFe/DAl) in the bcc_B2 phase.