High Temperature Behavior of Tungsten-Based Powder Alloy Joints Brazed with CuAgNi Solder

The microstructures of CuAgNi filler metals and tungsten-based powder alloy brazing joints were investigated by OM, SEM and XRD, to compare and analyze the high temperature shear strength of tungsten based powder alloy joints brazed with CuAg and CuAgNi filler metals, and the thermal fatigue properties of the brazed joints of CuAgNi brazed filler metal were further analyzed. The results show that Ni promotes the shear strength of brazed joints at room temperature and high temperature. When the temperature is close to room temperature, the shear strength of the brazed joint is 214.7 MPa, which is 32.37% higher than that without Ni. At 400 degrees C, the shear strength is 121.9 MPa, which is 91.67% higher than that without Ni. Moreover, when the temperature is beyond 300 degrees C, the oxidation of the bonding interface causes the bonding strength of the joint to drastically decrease. In the thermal fatigue test, as the number of thermal cycle increases, the cracks gradually expand after the initiation of alpha-Cu and beta-Ag bonding, which gradually reduces the shear strength of the joint.