Residual stresses in materials modified by plasma electrolytic oxidation: Insights and implications for performance

This review explores the significance of residual stresses determination in the performance and durability of materials modified by plasma electrolytic oxidation (PEO). The study highlights how residual stresses can critically affect mechanical properties and the fatigue behavior of PEO-coated components, based on different aluminum alloys, where a direct correlation between residual stress levels and fatigue performance has been established. The review also discusses residual stresses and their implications in magnesium and titanium-based materials. In the former, residual stresses have been shown to influence not only mechanical properties but also corrosion resistance, making the materials attractive for lightweight structures and biomedical applications. Overall, the review highlights the potency of the sin 2 Ψ method using X-ray diffraction for non-destructive measurement of residual stresses in PEO coatings. While this technique has gained popularity due to its relative simplicity, its application can be limited by measurement errors, particularly in multilayered microstructures, typical of PEO-coated samples. Therefore, advancements such as the extended sin 2 Ψ method, which allows for more localized sampling and analysis, are necessary for a comprehensive understanding of stress distributions. Future research directions are proposed, focusing on enhancing coating functionality and understanding the relationship between residual stresses and material properties across various substrates.