Effect of substrate bias on the microstructure, defect evolution and mechanical properties of Cr coatings during magnetron sputtering

Chromium (Cr) coatings on Zircaloy alloys are a leading candidate for accident tolerant fuel (ATF) cladding, where their performance under normal and loss-of-coolant accident (LOCA) conditions is governed by microstructure and defects. This work systematically investigates the effect of substrate bias (−30 V, −70 V, and −110 V) on the microstructure and mechanical properties of Cr coatings. Results demonstrate that increasing bias promotes significant grain coarsening within the coatings while concurrently reducing the density of internal defects. This phenomenon is attributed to the enhanced adatom surface diffusion induced by higher bias, which progressively mitigates the shadowing effect during deposition. Based on these findings, a mechanistic model elucidating the relationship between bias and coating growth evolution is established, providing a valuable reference for the practical design and optimization of Cr coatings for advanced nuclear fuel cladding applications.