Preparation and Characterization of Nickel-Based Brazing Powder and Paste for Wide Gap Repair on IN738 Alloy

In the present study, a nickel-based brazing paste were prepared and characterized. The mechanical alloying method was utilized to prepare the initial powder, and the commercial IN625 powder in different ratios was utilized for producing brazing pastes and wide gap brazing of IN738. Using the Taguchi method, a water-based binder was optimized to prepare the pastes. Then, the brazing pastes and related brazed joints were characterized. The joints' microstructure revealed the formation of three different zones. As the filler metals' low melting point particles (LMPs) increased, the number of chromium-rich boride phases increased. The binder with the composition includes 82.6 wt.% distilled water, 12.4 wt.% glycerin, 2.5 wt.% mineral oil, and 2.5 wt.% CMC has the optimal composition to convert nickel-based powders into brazing pastes. The preferable joints with minimum porosity are achieved using a filler composition containing 40 and 50 wt.% LMPs.