A way to evaluate the residual stress of ZrO ₂ coating deposited on GH3128 alloy by image relative method

Abstract The evaluation of residual stress originating from thermal expansion mismatch is very important to the reliability and durability of coated components in engineering applications. However, the way to evaluate the residual stress at high temperatures is full of challenges because of the limitations of the method and equipment. In this work, the image relative method was carried out to evaluate the residual stress of ZrO ₂ coating deposited on one side of GH3128 alloys with different thicknesses at high temperatures. Via the image relative method, residual stress at different temperatures could be calculated by using the contour method, which is based on the traditional Stoney's formula according to the measured curvature radius. Then, the temperature dependence of residual stress of specimens with different ratios of the cross‐sectional area of substrates to coating ( S _s / S _c ) was achieved. The findings demonstrate that residual stress decreased with the increase in temperature because of the stress relaxation. Moreover, the residual stress increased with the increasing value of S _s / S _c at the same test temperature. In addition, from the comparison of the pictures of specimens during the secondary cooling process, the temperature at which the coating starts to break off could be found intuitively to be 750°C.