Ni-based superalloys are used in applications requiring high creep resistance and good oxidation and corrosion resistance. After long-time exposure to service condition, they may need to be repaired by joining or welding. In this research, the effects of joining temperature (TJ) and time (tJ) on microstructure of the transient liquid phase (TLP) bonding of GTD-111 superalloy were investigated. The bonding process was applied using BNi-3 filler at temperatures of 1080, 1120, and 1160 °C for isothermal solidification times of 195, 135, and 90 min, respectively. Homogenization heat treatment was also applied to all of the joints. The results showed that intermetallic and eutectic compounds such as Ni-rich borides, Ni-B-Si ternary compound and eutectic-γ continuously are formed in the joint region during cooling. By increasing tJ, intermetallic phases were firstly reduced and eventually eliminated and isothermal solidification was completed as well. The results showed that with the increase of the holding time at all of the three bonding temperatures the thickness of the athermally solidified zone (ASZ) and the volume fraction of precipitates in the bonding area decrease and the diffusion affected zone (DAZ) width increases. Similar results were also obtained by increasing TJ from 1080 to 1160 °C at tJ = 90 min. Furthermore, increasing the TJ from 1080 to 1160 °C led to the faster elimination of intermetallic phases from the ASZ however, these phases were again observed in the joint region at 1180 °C. It was observed that by increasing the bonding temperature, the bonding width and the rate of dissolution of the base metal increase. Based on the results, increasing the homogenization time from 180 to 300 min led to the elimination of boride precipitates in the DAZ and a highly uniformity of the concentration of alloying elements in the joint region and the base metal.

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