Layering Ni to mediate the Kirkendall effect (KE) in cu/ta nonequilibrium diffusion for enhanced abrasion resistance

Abstract

This study delves into the KE occurring at the interface of the Cu/Ta system during thermal diffusion, along with the mediating impact of integrating a Ni interlayer on the nonequilibrium diffusion of Cu/Ta. In the Cu/Ta system, nonequilibrium thermal diffusion results in the generation and aggregation of Cu side Kirkendall voids (KVs). In the Cu/Ni/Ta system, the Ni interlayer ensures the equilibrium of system atom migration through the movement and annihilation of vacancies, thereby enhancing the bonding between the layers. Calculations of interdiffusion coefficients using the Boltzmann-Matano (B-M) method reveal that interdiffusion coefficients at the coating-substrate interface are 4–5 orders of magnitude higher for the Cu/Ta system compared to the Cu/Ni/Ta system. The analysis of mean square displacement (MSD) and radial distribution function (RDF) provides insights into the role of the Ni interlayer as a potential barrier mediating the atomic-level diffusion behavior of the system. Moreover, the Cu/Ni coating exhibits superior abrasion resistance and bond strength compared to the Cu coating, attributed to the inhibition of KVs generation at the interface. This exploration introduces a novel approach to inhibit defects stemming from the KE and advances comprehension of interfacial phenomena in composites.