Preparation and Property of α-Al ₂O ₃ Diffusion Barrier on 316SS

In this paper, a compact and adherent Al2O3 diffusion barrier was successfully obtained between a Ni coating and 316 stainless steels (316SS) through double-pulse composite plating coupled with in-situ thermal grown technique. In order to promote the formation of α-Al2O3 at a lower temperature, a Cr2O3 film was firstly prepared by the pre-oxidation of the 316SS. Then a Ni–Al/NiO composite coating was deposited on the 316SS in the modified Watts’ bath with a Zeta potential of about +21.89 mV, a favorable condition for the co-deposition of the double particles and nickel, followed by the heat treatment in Ar at 800 °C for 12 h. The results of the diffusion resistance tests conducted at 750 and 800 °C for 100 h in argon suggest that the Ni/α-Al­2O3 composite coating changes little during the annealing treatment and significantly prevents the diffusion of Fe and Cr from the 316SS substrate to the upper Ni layer.