Effect of bonding time and temperature on microstructure of GTD-111/ BNi-3 /GTD-111 systemduring the Transient Liquid Phase (TLP)

In this paper, the effect of bonding temperature and time on the microstructure of transient liquid phase bonding of GTD-111 nickel-based superalloy was studied. The bonding process was performed at temperatures of 1080, 1120 and 1160 °C at different times and the microstructure of the various bonding regions was analyzed by light and scanning electron microscopy. The results show that by increasing the bonding temperature from 1080 to 1160 °C, solidification time was reduced from 195 to 90 min and the dissolution rate of the base metal and the bonding width increased. Also, at all holding times, the bonding zone containing secondary phases included nickel-rich and chromium-rich borides and nickel silicide in a  matrix. These phases were observed in the centerline and adjacent of the interface. By increasing the bonding time, the volume fraction of the precipitates in the bonding zone decreased and the brittle boride phases were completely removed. This process is due to the strong dependence of the diffusional behavior of the TLP-joint on temperature and time. It was observed that with increasing the bonding temperature, the bonding width and the rate of dissolution of the base metal increase. The results showed that with increasing holding time at all three bonding temperatures, the thickness of the ASZ zone and the volume fraction of precipitates in the bonding area decreased and the DAZ width increased.