Abstract

Thermal barrier coatings (TBCs) protect turbine engine components by enabling operation at high temperatures, thereby improving turbine efficiency and fuel economy. Suspension plasma spraying (SPS) enables the formation of columnar microstructures with controlled porosity, thermal stresses, and low thermal conductivity. However, the columnar structure also promotes calcium–magnesium–alumino‑silicate (CMAS) penetration, which accelerates TBC degradation. To address this limitation, laser post‑treatment has been proposed to re‑melt and densify the coating surface.
In this study, columnar yttria‑stabilized zirconia (8YSZ) topcoats were deposited using SPS. A CO₂ laser was employed to produce a re‑melted surface layer on the columnar coatings. Laser glazing significantly reduced surface roughness, sealed open porosity, generated a dense microstructure, and increased microhardness. The effects of key laser parameters, including scanning speed and laser power, on the microstructure of the re‑melted layer were systematically investigated. Results showed that increasing scanning speed led to an increase in crack width within the re‑melted zone. Phase analysis confirmed that the phase composition remained stable, with the metastable tetragonal (t′) phase retained after laser treatment.
CMAS corrosion tests revealed extensive CMAS penetration in as‑sprayed coatings due to their porous microstructure, whereas laser‑glazed coatings exhibited significantly reduced infiltration. CMAS elements were detected only within vertical cracks in the glazed layer, which served as the primary penetration pathways. Notably, the laser‑glazed layer maintained its structural integrity even after four hours of CMAS exposure.