Wide gap brazing of NIMONIC 105 superalloy using BNi-2 filler and the effect of post braze heat treatment on joint properties

Wide gap brazing is a critical, cost-effective, and widely used technique for repairing superalloy components. However, even with careful control of the braze filler and brazing variables, formation of intermetallic phases cannot be completely avoided. In this work, wide gap brazing of NIMONIC 105 superalloy was performed in a vacuum chamber using BNi-2 alloy as filler at two different brazing temperatures of 1050 degrees C and 1170 degrees C. Then, the innovative approach of post braze heat treatment (PBHT) of diffusion-brazed bonds performed at 1000 degrees C to improve the joints' microstructural characteristics and mechanical properties. The phases formed in the diffusion-affected zone (DAZ), isothermally solidified zone (ISZ), and athermally solidified zone (ASZ) were comparatively studied. The investigation confirms PBHT led to a more uniform hardness profile across the joint and a more homogenous interface region via dissolution of intermetallic phases that, in turn, increases the resistance to oxidation. The shear strength of joints made at brazing temperature of 1170 degrees C remarkably increased from 40 to 83.8 MPa and finally reached the maximum value of 92.2 MPa via PBHT. The ductility of this specimen was as high as 19.0%, which is approximately 75% of the ductility of the base metal.