Epitaxial Stabilization and Radiation-Stimulated Segregation in CA-PVD AlN/CrN Multilayer Coatings Under Ion Bombardment

Abstract

This paper investigates the regularities governing the formation of the atomic-crystalline architecture, surface topography, and chemical composition of AlN/CrN multilayer coatings deposited via cathodic arc physical vapor deposition onto AISI 321 austenitic stainless-steel substrates. The synergistic effect of the negative substrate bias voltage (–50, –100, and –200 V) and the deposition duration of individual AlN layers (10, 40, and 60 s) on the kinetics of phase competition and the evolution of radiation-stimulated nanostructures was analyzed. Using X-ray diffraction and scanning electron microscopy, combined with energy-dispersive X-ray spectroscopy, it was established that at low deposition energies (–50 V, 10 s), the epitaxial template effect of the c-CrN matrix dominates, thereby stabilizing the metastable cubic c-AlN phase. Increasing both the layer thickness and the substrate bias to –100 V leads to the breakdown of pseudomorphic growth and transitions the system into a possible nanocrystalline or quasi-amorphous state. At high bias potential of ‑200 V, complete thermal relaxation occurs, accompanied by a textured phase transition of AlN into its stable hexagonal wurtzite modification (h-AlN). A counterintuitive decrease in the aluminum concentration (from 46.88 to 33.72 at. %) despite the prolonged growth time was observed. This phenomenon is driven by the selective re-sputtering of lighter Al atoms under the influence of a high-energy ion flux. Furthermore, radiation-stimulated interdiffusion of iron from the substrate into the coating, along with an ion-cleaning effect that removes interstitial carbon impurities from the matrix, was recorded. The insights obtained expand current understanding of non-equilibrium solid-state thermodynamics and open new possibilities for the precision tailoring of nanostructured protective coatings by optimizing ion-plasma parameters.