Regulation of Ag atom diffusion in CrAlN-Ag coatings based on diffusion mechanism

Abstract

The diffusion of solute atoms at grain boundaries significantly impacts material properties. This study employed magnetron sputtering to prepare CrAlN-Ag coatings on silicon nitride substrates. Comprehensive characterization was conducted on the surface and cross-sectional morphologies of the coatings, as well as the concentration distribution of Ag elements along the coating depth direction. The diffusion mechanism of Ag atoms at the Σ5(012)[100] grain boundary and CrAlN(100) surface was analyzed using ab initio calculations. Based on this understanding, the distribution of Ag elements in the coatings was regulated. The results indicate that the Ag nanoparticles on the coating surface originate from the migration of Ag atoms from within a 260 nm depth range of the coating. The energy barrier for Ag atoms migrating along grain boundaries is .98 eV, suggesting that grain boundaries serve as rapid pathways for Ag atoms migrating toward the surface. Additionally, vacancy defects at grain boundaries and surfaces create energy traps that restrict the free diffusion of Ag atoms. Based on this mechanism, the stoichiometric deviation of N elements in the coatings was regulated. For the coatings after regulation, the size of surface Ag particles decreased, and the mechanical properties and wear resistance were improved.