Wetting and brazing characteristic of high nitrogen austenitic stainless steel and 316L austenitic stainless steel by Ag–Cu filler

Abstract In the present work, wetting behaviour of Ag–Cu eutectic filler on high nitrogen austenitic stainless steel (HNS) and 316L austenitic stainless steel (316L) base metals was firstly studied using a sessile drop method in high vacuum. The Ag–Cu eutectic filler exhibits completely different dynamic wetting process on the surface of HNS and 316L. The equilibrium contact angle of Ag–Cu/HNS system is lower and its wetting time is shorter than that of Ag–Cu/316L system. Subsequently, brazing experiments were carried out for HNS and 316L base metals using the same filler at 840 °C for a holding period of 5–30 min under high vacuum. Microstructural analysis shows that the 316L/316L joints are composed of α-Cu and fine Ag–Cu eutectic. The HNS/HNS joints consist of β-Ag and coarse Ag–Cu eutectic. The optimal shear strength of HNS/HNS joints (290 MPa) is significantly higher than that of 316L/316L joints (175 MPa) because of the formation of diffusion layer. Therefore, HNS has tremendous potential to take the place of the traditional austenitic stainless steels for industry application.