Unveiling the effect of Ni interlayer on diffusion bonded reduced activation Cr0.8FeMnNi medium entropy alloy/316 stainless steel joint: Interfacial microstructure, diffusion behavior and mechanical properties

Abstract

This study explored the diffusion bonding of Cr0.8FeMnNi medium entropy alloy to 316SS with and without a Ni interlayer using spark plasma sintering. Direct bonding led to the formation of Cr2O3 and Mn3O4 oxides at the interface, resulting in stress concentration and reduced tensile strength. However, the introduction of a Ni interlayer effectively reduced oxide size and improved mechanical properties by accelerating diffusion and relieving stress concentrations. Optimal joints were achieved at 820 °C / 60 min / 25 MPa, producing joints with tensile strength and elongation comparable to 316SS. Furthermore, diffusion behavior, growth kinetics of diffusion layers, and activation energy of diffusion in various atoms and layers were analyzed. The activation energy of each element in the joints with Ni interlayer was decreased compared to direct diffusion bonding. This research highlights the significance of interlayer in enhancing diffusion bonding outcomes for nuclear power applications.