Effect of magnetic unbalance coefficient in magnetron sputtering on CrN coating microstructure and properties: A multi-scale simulation and experimental study

ZH Ren and LW Zheng and GG Wang and YH Cao and HJ Chen and SS Xu, SURFACE & COATINGS TECHNOLOGY, 518, 132904 (2025).

DOI: 10.1016/j.surfcoat.2025.132904

This study systematically investigates the influence of the unbalance coefficient (K) in unbalanced magnetron sputtering (UBMS) on the microstructure and properties of chromium nitride (CrN) coatings through integrating multi-scale simulations with experimental characterization (FESEM, AFM, GIXRD, nanoindentation). Experimentally, CrN coatings prepared in high-K UBMS exhibit enhanced (200) crystallographic orientation, refined column-free grains, smoother surfaces (RMS roughness of 2.9 nm), a high hardness of 24.33 GPa and a minimized wear rate of 1.6 x 10-7mm3 center dot N-1 center dot m-1. In terms of simulation, a framework that combines PIC-MCC for plasma discharge, Monte Carlo for sputtering and transport, and molecular dynamics for coating growth, is developed to model the physical processes across scales. The simulations results reveal that the increased expansion of plasma toward the substrate under high-K configuration significantly intensifies ion bombardment on the deposited atoms, increasing ion-to- atom energy ratio (Eion) by over 36-fold. This increasing energy input drives the coating growth mechanism from the Volmer-Weber island mode to a layer-by-layer growth mode, contributing to microstructural densification and improved mechanical performance. These findings clarify the relationship between magnetic field configuration, plasma behavior, and coating performance, providing guidance for the rational UBMS design and optimizing coating properties for tribological applications.

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