Current-enhanced long-range diffusion of interface atoms to tailor coating structure and properties

Abstract

Coating modification is an important step for some engineering materials to achieve specific service performance indicators. However, most traditional technologies have disadvantages such as poor diffusion kinetics, degradation of substrate performance under high-temperature, and complex processes. Here, a general approach is proposed to realize coating structure and performance tuning via electromigration, taking 316 stainless steel with aluminide coating as an example. After the pulsed electric current treatment, the α-Al2O3 layer with high resistance tritium factor was formed on the surface of the coating at lower-temperature and shorter-time (about 1000 °C for a few minutes), while the conventional heat treatment required long-time and high-temperature treatment (above 1200 °C for several hours). Moreover, electropulsing apparently accelerated the interdiffusion of atoms. Numerical simulation results show that through the coupling of current density gradient and chemical potential gradient, the diffusion flux of atoms at the interface is significantly increased, which promotes long-range diffusion of atoms and improves the bonding force between interfaces. Pulsed current not only optimizes the structure of the interface by accelerating the diffusion of atoms, but also forms a α-Al2O3 layer due to the long-range diffusion of atoms, which is of great significance to the research and application of aluminide tritium permeation barrier coatings.