Microstructure and Microhardness of 316L Stainless Steel Joint Seam Vacuum Brazed by BNi7 Ni-Based Filler Metal

Vacuum brazing of 316L stainless steel with BNi7 Ni-based filler metal was carried out. The influences of brazing clearance and holding time on microstructure, element distribution and microhardness of the joint seam were studied by optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and microhardness test. The results show that the joint seam was comprised of Ni-Fe based solid solution and intermetallic compounds. The content of intermetallic compounds decreased with the increase of brazing clearance, and decreased with the prolongment of brazing holding time. When the brazing clearance and holding time were 40 μm and 60 min respectively, the content of intermetallic compounds was the least and the hardness distribution was more uniform.