Phase and Microstructural Evolutions and Fracture Behavior of Nimonic 75 Transient Liquid Phase Joints at Different Temperatures

In this research, the transient liquid phase bonding process on Nimonic alloy 75 was investigated using an AWS BNi-2 interlayer with a 32 μm thickness. The transient liquid phase bonding process was performed at 1050 °C, 1100 °C, and 1150 °C for 60 min. X- ray diffraction (XRD) technique was employed to identify the Boride phases in the joint area. For the Nimonic 75 alloy, the experimental results showed that the temperature and time have an evident effect on the phase constituents of the Boride phases, i.e., CrB and Ni2B. Also, the shear strength of TLP joints was measured. The results indicated that the joint microstructure consisted of three zones, including isothermal solidification zone (ISZ), thermal solidification zone, and diffusion affected zone. The diffusion affected zone of the Nimonic 75 alloy was vanished and the homogenization process occurred by increasing the bonding time. The results of shear strength showed that the bonding strength was increased from 63 MPa to 152 MPa with increasing the bonding temperature from 1050 to 1150 °C, respectively. Analysis of fracture surfaces showed that the fracture mode changed from brittle, semi-brittle and finally ductile mode by increase in bonding temperature which is due to the decrease in volume fraction of brittle intermetallic phases and eutectic structureany sort of image, illustration, figure, or table.