Creep Behavior of Diffusion-Welded Alloy 617

Plate-type heat exchangers are anticipated to be used in the next-generation nuclear industry, and solid-state diffusion welding is a critical technology for building plate-type heat exchangers with high integrity. In this study, we manufactured a diffusion weldment and evaluated its creep behavior. Microscopic analysis revealed that Al-rich oxides were developed along the interface, significantly impeding grain-boundary movement across the interface. Oxide-containing planar grain boundaries resulted in premature brittle fracture at the interface with less than 9% creep strain under all test conditions. The time to rupture and time to 1% creep strain of the diffusion weldment were less than those of the as-received alloy, while the slopes in double-logarithmic plots were almost identical for both alloys. In a Larson–Miller parameter study, the stress to rupture of the diffusion weldment reached 95.59% of that of the as-received alloy, whereas the stress to 1% creep strain steeply decreased in the low-stress range.