IN-738LC nickel-based superalloy was joined by transient liquid phase diffusion bonding
using AMS 4777 filler alloy. The bonding process was carried out at 1050 °C under vacuum
atmosphere for various hold times. Microstructures of the joints were studied by optical and
scanning electron microscopy. Continuous centerline eutectic phases, characterized as
nickel-rich boride, chromium-rich boride and nickel-rich silicide were observed at the
bonds with incomplete isothermal solidification. In addition to the centerline eutectic
products, precipitation of boron-rich particles was observed in the diffusion affected zone.
The results showed that, as the bonding time was increased to 75 min, the width of the
eutectic zone was completely removed and the joint was isothermally solidified.
Homogenization of isothermally solidified joints at 1120 °C for 300 min resulted in the
elimination of intermetallic phases formed at the diffusion affected zone and the formation
of significant γ′ precipitates in the joint region.