Effect of transient liquid phase diffusion bonding on properties of ODS nickel alloy MA758

An oxide dispersion strengthened (ODS) MA758 nickel alloy was bonded in the fine grain and recrystallised conditions using transient liquid phase diffusion bonding at 1100 degreesC for various hold times. A microstructural study was undertaken to investigate the effect of post-bond heat treatments at 1360 degreesC for 1 h and changes in parent metal grain size on developments of bond microstructure. Shear and fatigue tests were carried out to determine the mechanical integrity of the bonded samples. Results showed that shear and fatigue strengths of diffusion bonds made in the recrystallised condition were higher than those of bonds made in the fine grain condition. The results from oxidation tests performed at 1000 degreesC show that the oxidation rate for samples bonded in the fine grain condition is higher than for those bonded in the recrystallised condition. However, localised oxidation of the joint region was not observed and this indicated that compositional homogeneity across the diffusion bonds had been attained.