Removing of Surface Oxide Film of SUS316 and Improvement of Diffusion-Bondability of A6061 Aluminum Alloy to SUS316 Stainless Steel using Surface-Activated Pre-Coating Technique

Study on Diffusion Bonding of Aluminum Alloy to Stainless Steel (Report 3)

Abstract

The diffusion-bondability of A6061 aluminum alloy to SUS316 stainless steel has been improved by using surface-activated pre-coating technique for SUS316 stainless steel. The surface-activated treatment for SUS316 was carried out by series of steps as alkaline cleaning → electrolytic cleaning HCl activating → metal-striking prior to diffusion bonding. Diffusion bonding of A6061/SUS316 was conducted at 758 K-823 K for 0.6 ks-7.2 ks applying 9.8 MPa in vacuum. ESCA analyses revealed that the surface oxide film could be removed by surface-activated pre-coating treatment and that striking insert metals would act as a barrier to reoxidation of SUS316. The tensile strength of A6061/SUS316 joints using Ag, Cu and Ni striking insert metals was risen up to about 100 MPa bonded at 758 K for 0.6 ks indicating nil joint strength in direct-bonding situation. The reaction layer growth in A6061/Ag striking/SUS316 joint was followed by the parabolic growth law, and the incubation time for reaction layer growth using Ag striking insert metal was shortened compared with direct-bonding situation.