Microstructure and mechanical properties of Si3N4/42CrMo joints brazed with TiNp modified active filler

Si3N4 ceramic/42CrMo steel joints were obtained by employing TiNp modified Ag–Cu–Ti active filler and subsequently the effect of TiNp content on the microstructure and mechanical properties of the joints was investigated. Microstructural examination revealed that TiN+Ti5Si3 reaction layer was adjacent to the Si3N4 ceramic while a TiC reaction layer was close to the steel substrate. With the increase of TiNp content, more fine grains and less Ag–Cu eutectic appeared in the joint and the reaction layers near the two base materials became thinner. The flexural strength of the joint obtained by four-point bending test climbed about 100% with the optimum TiNp content of 5 vol%, comparing with the case without TiNp. Thermal stress distributions in the joint were analyzed using finite element modeling computations, which accorded well with the bending test results.