Microstructure development during transient liquid phase bonding of GTD-111 nickel-based superalloy

Abstract

Transient liquid phase (TLP) bonding was used to join a nickel-based superalloy GTD-111 using a Ni–Si–B amorphous interlayer, MBF30. Bonding was carried out at 1100 °C with different holding time under vacuum. Joint region microstructure was studied by optical and scanning electron microscopy. Microstructural studies showed that before completion of isothermal solidification, bond region consists of four distinct zones: centerline eutectic structure due to athermal solidification, solid solution phase due to isothermal solidification, diffusion-induced boride precipitates and base metal. Complete isothermal solidification, which prevents formation of centerline eutectic constituent, occurred within 75 min at 1100 °C. Homogenization of isothermally solidified bonds at 1150 °C for 240 min resulted in reducing of secondary precipitates in diffusion affected zone and formation of significant γ′ precipitates in the bond region.