Microstructure and strength of high nitrogen steel joints brazed with Ni-Cr-B-Si filler

Abstract

Brazing of high nitrogen austenitic stainless steels was carried out by using Ni-Cr-B-Si filler metal. The effects of brazing temperature (1020–1100°C) on the microstructure and shear strength of the joints were investigated. The results show that BN compounds with hexagonal structure are formed at the interface by the reaction of N from substrate and B from filler. The brittle Cr5B3 compounds with high microhardness are observed in the centre of brazing seam. The BN content increases and the Cr5B3 content decreases with the increase in brazing temperature. However, the content of BN compounds played a determinable role on the joint strength. The optimal shear strength of joints was 176.7 MPa when the joining temperature was 1020°C.