Microstructure design of the laser glazed layer on thermal barrier coatings and its effect on the CMAS corrosion

Highlights: • As-sprayed thermal barrier coatings (TBCs) are severely attacked by CMAS. • Laser glazing could improve CMAS resistance of TBCs, but the open channels provide the path for melt penetration. • TBCs are designed to have double laser-glazed layers, in which the vertical cracks are bifurcated and staggered. • TBCs with double laser-glazed layers highly resist to CMAS penetration. • Laser surface modification combining with double laser-glazed layers design is a promising method to alleviate CMAS attack to TBCs. Calcium-magnesium-alumina-silicate (CMAS) corrosion is a great challenge for the long lifetime of thermal barrier coatings (TBCs). In this study, the surface microstructure of TBCs is tailored by laser glazing to improve the CMAS resistance, and the modified coatings are designed to have single and double laser-glazed layers. In the double laser-glazed coating, the vertical cracks in the glazed layer which penetrate directly for the case of the single laser-glazed coating become bifurcated and staggered. Under molten CMAS conditions, the coating with double laser-glazed layers highly resists to melt penetration, and the glazed layer exhibits excellent phase stability and structural integrity.