Microstructure and shear strength of brazed joints between Ti(C,N)-based cermet and steel with Cu[sbnd]Ag[sbnd]Ti filler metal

Abstract

Microstructure and shear strength of Ti(C,N)-based cermet/Cu30Ag3Ti filler metal/W9Mo3Cr4V steel joints were investigated after brazing in vacuum at 870, 910, and 950 °C for 20 min, and 910 °C for 10, 20, 30 and 40 min. The reaction layer of CuNiTi solid solution between cermet and filler metal was difficult to form during brazing at 870 °C, leading to very low shear strength of joints. During brazing at 910 °C, CuNiTi solid solution was formed between cermet and filler metal, and it became thick with the increase of holding time. Shear strength of joints reached a peak value for 30 min, due to the appropriate thickness of CuNiTi solid solution. During brazing at 950 °C, CuNiTi solid solution was formed and then grew on the whole along with Ag-based solid solution in filler metal, but was not formed between cermet and filler metal, thus deteriorating shear strength of joints.