Thickness-dependent dual-failure mechanisms of chromium coatings on gun barrel under high temperature thermal shock test

This study investigates the thickness-dependent failure of chromium coatings under thermal shock, designed to simulate the firing process of gun barrel. Using a thermal shock testing system on specimens with coating thicknesses of 50 μm, 80 μm, and 110 μm, we characterised the microstructural evolution and interfacial stress via SEM, EDS, and XRD. Results show that failure is dominated by transverse oxygen diffusion at thicknesses ≤ 50 μm, whereas macro-delamination occurs at ≥100 μm due to elevated interfacial thermal stress. An optimal thickness of ≈80 μm balances oxidation resistance and mechanical integrity. This work develops a mechanistic model that characterises these non-linear failure processes to define an optimised thickness range of 60–100 μm for ballistic reliability.