Joining of stainless steel (SS304) and OFE copper by vacuum brazing

Abstract This paper describes the vacuum brazing process for joining OFE copper with stainless steel (SS 304) using silver based filler material (68Ag27Cu5Pd). Vacuum brazing of SS304 and OFE copper was carried out in a vacuum furnace at a vacuum level of 10−6 mbar. The peak brazing temperature was kept as 920 °C with a soaking time of 10 min. This combination is often used in bi-metallic joints for high vacuum applications. Optimization of brazing parameters was done to produce defect free joints. Micro structural analysis of the brazed joint was carried out using optical and scanning electron microscope. The flow of filler material and diffusion of its elements into substrates was observed. The brazed joint was found to be of good quality and free from any major cracks. The micro hardness was evaluated across the interface and it was observed that hardness decreases towards the interface. The hermeticity of the joint was investigated using helium spray method.