Effect of bonding temperature on transient liquid phase bonding behavior of a Ni-based oxide dispersion-strengthened superalloy

The effect of joining temperature on the transient liquid phase (TLP) bonding of MA758 superalloy was investigated. The TLP bonds were made at temperatures of 1100 and 1200 °C. Analysis was undertaken to determine the changes within the joint microstructure. The bonding temperature affected the extent of parent metal dissolution, the time for isothermal solidification, and the attainment of microstructural continuity across the joint region. Bonding at 1100 °C did not result in extensive parent metal dissolution, and subsequent shear testing showed failure through the center of the joint. However, bonding at 1200 °C increased parent metal dissolution resulting in significant agglomeration of Y2O3 particles at the joint interface. Failure was observed along the joint interface in regions depleted of strengthening particles. Bonding at a higher temperature reduced the time for isothermal solidification but also reduced the strain energy of the oxide dispersion-strengthened alloy so that grain growth across the joint region could not be achieved.