Microstructure, corrosion behavior and mechanical properties of 1Cr18Ni9Ti 1 stainless-steel joints brazed with BNi-2 filler metal

This study investigates the corrosion behavior and mechanical property degradation of BNi-2 vacuum-brazed 1Cr18Ni9Ti joints under salt spray exposure. Shorter holding times (10–30 min at 1050 °C) promote blocky Cr-borides formation within the brazing seam center, along with finer Cr-borides at the braze interface and base material diffusion zone. In contrast, extended holding times (60 min) significantly suppress the formation of borides. Corrosion initiates at the interface zone before propagating into the adjacent diffusion zone, driven primarily by micro-galvanic coupling between Cr-borides and the surrounding Cr-depleted substrate. Macro-galvanic effects between the joint and base material are negligible. Increasing holding time enhances corrosion resistance by reducing Cr-boride formation. Critically, prolonged holding time (60 min) minimizes post-corrosion mechanical degradation, yielding optimal properties: 291 MPa yield strength, 505 MPa tensile strength, and 11.2% elongation.