Microstructural evolution and mechanical properties of micro-deformation diffusion bonding Inconel 617 superalloy

This study explicates the microstructural evolution and mechanical properties of the Inconel 617 joint, prepared through micro-deformation diffusion bonding. The joints were fabricated with a uniaxial deformation less than 2%. An interface without interfacial voids was achieved when the bonding temperature was increased from 1100 to 1150 degrees C. The microstructure of the joint devolved at 1150 degrees C under a holding time of 60 min, comprised of grain boundaries (GB), Cr-rich M23C6 carbides, and alpha-Al2O3 oxides. The similar microstructure was also observed in the joint prepared at 1150 degrees C with an incubation time of 180 min. As the bonding temperature was increased to 1180 degrees C, a continuous network of the M23C6 carbide was nucleated along the bonding interface, accompanied by the grain coarsening, up to 3 times that of pre-bond substrate. The formation of the M23C6 and Al2O3 particles was governed by the diffusion and segregation of Cr, C, Al, and O along the bonding interface. The pinning effect of interfacial precipitates, the M23C6 and Al2O3 particles, inhibited the migration of GB across the bonding interface. The cracks were initiated and propagated along the bond line. The optimum combinations of strength, plasticity, and impact toughness were obtained for the two joint configurations, prepared at 1150 degrees C with the holding times of 60 and 180 min, respectively. A quasi-cleavage mode of fracture was revealed, consisting of cleavage planes as well as ductile dimples.