Creep properties of Ni-based superalloy GTD-111 joints produced by transient liquid phase method using BNi-3 filler

In this paper, the effects of temperature and bonding time on creep behavior of nickel-based superalloy GTD-111 joints produced by transient liquid phase (TLP) process were studied. The bonding process was performed using BNi-3 filler at temperatures of 1080, 1120, and 1160 degrees C and isothermal solidification times of 195, 135, and 90 min, respectively. Homogenization heat treatment was also applied to all joints. Afterward, creep test was performed in 982 degrees C/152 MPa condition on the base metal and joint samples. The microstructure of joints fractured in the creep test was investigated by optical and scanning electron microscopy. Microhardness results of the TLP-bonded samples showed that the hardness decreases with increasing the distance from the bonding interface to the substrate at all the three bonding temperatures. It was observed that creep failure of all specimens occurs in the joint region and the creep ductility of the joint samples is much lower than that of the base metal. Moreover, it was observed that with increasing bonding temperature from 1080 to 1160 degrees C, the creep failure time decreases from 26 to 6 h, the percentage of primary gamma' phase after creep deformation decreases from 35.08-31.12 vol.%, and the size of primary gamma' precipitates increases from 907 to 1251 nm.