Wear-Induced Interfacial Diffusion in TiN Coatings: A Molecular Dynamics Study

Understanding the relationship between structural degradation and atomic diffusion is essential for elucidating coating failure at solid interfaces. However, the atomic-scale connection between wear and diffusion remains unclear under coupled thermo-mechanical conditions. In this work, molecular dynamics (MD) simulations combined with first-principles calculations are employed to investigate the wear behavior and interfacial diffusion mechanisms in TiN coatings. The results reveal that wear originates from the coupled effects of mechanical loading and plastic deformation, accompanied by dislocation evolution and work hardening in the adjacent material, thereby enhancing interfacial interactions. More importantly, the coating failure is governed by atomic-scale amorphization, where progressive distortion and breaking of Ti-N bonds lead to the loss of long-range crystalline order. This structural degradation not only represents the intrinsic origin of wear but also facilitates atomic diffusion by reducing local lattice constraints. Furthermore, the diffusion of Ni, Cr, and Fe atoms is not spontaneous but is driven by wear-induced structural degradation, which occurs preferentially in amorphous and defect-rich regions. In these locally destabilized regions, the diffusion formation energies of the atoms are significantly reduced, thereby promoting interfacial atomic migration. These findings establish a clear atomic-scale correlation between wear and interfacial diffusion in TiN coatings.