Microstructural evolution and failure mechanisms of thermal barrier coatings under extreme environmental conditions

To study the failure mechanisms of thermal barrier coatings under extreme conditions, GYYSZ and GYYSZ/YSZ TBCs with different porosity were prepared on a GH3536 substrate via atmospheric plasma spraying. Samples were evaluated using a burner rig test at high temperatures with a large temperature gradient. The microstructural evolution and the failure mechanisms were discussed. Results show that the surface temperature of the coatings reaches 2350℃, leading to sintering in the upper region. SCL TBC lifespan is 2 cycles, with early delamination caused by sintering-induced transverse cracks and overall coating spalling of coating resulting from thermal mismatch–induced transverse cracks. Low-, middle-, and high-porosity DCL TBC's lifespans are 1, 3, and 3 cycles, respectively. The failure of DCL TBC is primarily due to delamination caused by sintering. Increasing the porosity of the top layer can delay the sintering process and enhance the anti-sintering ability of the coating.