A Study Of Residual Stress Of The Brazing Joint Between Cemented Carbide And Steel

Residual stress of the brazing joints between YG8 cemented carbide and A3 steel were studied in this paper by using CuZnMn filler alloys. Through numerical simulation and measurements, the magnitude and distribution of residual stress was analyzed. The effects of deep-cooling treatment and applied loads on the residual stress, interfacial microstructure and bond strength were also examined. The mechanism to reduce residual stress was discussed.By means of finite element analysis method, distribution of residual stress was analyzed. The results showed that a large stress gradient existed in the cemented carbide at room temperature, and there was a maximum residual stress in the cemented carbide near the filler alloys.Using nano-indentation method, residual stress in the cemented carbide near breakpoint was measured for the first time. The result was consistent with the finite element analysis. Near the filler alloys, the maximum residual stress in cemented carbide was the main reason for the break of the cemented carbide. According to the SEM backscattered electron images, the molten filler alloys can effectively wet YG8 and A3 steel. And there were no microcracks, inclusions, intermetallic compound etc. nearby the interface. The joints combined well.The residual stress after a postweld deep-cooling treatment was investigated. It was found that after the deep-cooling treatment, the residual stress reduced and the shear strength enhanced. Annealing treatment further enhanced the shear strength of the joint. The enhanced shear strength by once temper and twice temper was 49.2% and 56.2% respectively. At the cemented carbide and filler alloys interface, there was diffusion of Cu and Zn elements.For the applied loads during brazing time, it was found that the thickness of the joint reduced with increasing pressure. When the load was applied at 200℃, the residual stress reduced with increasing pressure and the shear strength enhanced. With the pressure was 160MPa, the maximum shear strength reached 247MPa. When the load was applied at 800℃, with increasing the pressure, the residual stress reduced and then increased, while, the shear strength enhanced and reduced later.