Evaluation of the Residual Stress in ZrO₂ Coatings Deposited on Different Substrates Through Image Relative Method

In this work, the influences of substrate characteristics on the deformation and residual stress in ZrO₂ coatings deposited on one side carbon steel, 316 stainless steel and 304 stainless steel are analysed via the image relative method. Based on the changes in bending deflection at different temperatures, temperature dependence of the residual stresses in the above three specimens was achieved through Stoney's formula. Results show that a compressive residual stress is generated during the cooling process because the ZrO₂ coating has a lower coefficient of thermal expansion (CTE) than that of the substrates. Additionally, by comparing the images of specimens under different temperatures, it can be found that the difference in CTE (∆α) between coating and substrate, as well as the temperature difference (∆T) between zero-stress temperature and testing temperature, determine the residual stresses in the coated specimens. And the higher the ∆α and ∆T, the higher the residual compressive stress and bending deflection. Moreover, temperature dependence of the residual stress could also be found through the image relative method.