X-Ray and Scanning Electron Microscopy Study of the Microstructure of Thermal Barrier Coatings

The thickness, cracks, pores, and porosity of high-temperature ceramic thermal barrier coatings are critical parameters for evaluating their thermal barrier performance. This study focuses on three-layer thermal barrier coatings, investigating their morphology, thickness, pores, and porosity from two-dimensional and three-dimensional perspectives using 3D X-ray microscopy and scanning electron microscopy. Secondary electron and backscattered electron scanning analyses of the coatings before and after service reveal a dense self-healing layer structure and the existence of porous defect areas in the inner layer. The three-dimensional images collected by 3D X-ray microscopy reveal microstructural information, such as cracks and pores, on a large scale. Through grayscale value analysis, the density and strong oxygen resistance of the self-healing layer were evaluated, and the bonding strength between the functional coatings was estimated by comparing their grayscale value differences. The results indicate that the findings from the two techniques are basically consistent, providing a feasible strategy for the comprehensive analysis of the microstructural characteristics of high-temperature ceramic thermal barrier composite coatings.