81 / 2024-09-27 16:52:35

Improving the thermal cycling-CMAS lifetime of TBCs by adjusting porosity

Keywords: Thermal barrier coatings; Thermal cycling-CMAS lifetime; Failure behavior; porosity

Atmospheric plasma spraying (APS) was used to fabricate 8YSZ (6-8 wt% Y₂O₃-ZrO₂) series coatings with different spraying parameters. Effects of spraying power and powder feed distance on the microstructure, performance and CMAS (calcium-magnesium-alumino-silicate) corrosion resistance of thermal barrier coatings (TBCs) is investigated. The application of coatings at higher spraying powers resulted in enhanced thermal conductivity, hardness, and elastic modulus. It is noteworthy that coatings sprayed at 39-40 kW displayed the highest thermal cycling-CMAS lifetime and CMAS penetration depth. Additionally, a series of embedded micro-aggregated particles (EMAP) coatings was created using different powder feed distances. The porosity of EMAP coatings was significantly higher than that of conventional YSZ coatings, with the EMAP coating produced at a 30 mm powder feed distance showing the highest porosity—approximately 2.5 times greater than that of traditional YSZ coatings. Compared to conventional YSZ coatings, the thermal cycling-CMAS lifetime for the coatings with 30 mm and 40 mm powder feed distances improved by 30% and 55%, respectively. This enhancement is attributed to the increased porosity, which boosts the strain tolerance of the coatings. However, the higher porosity also facilitates CMAS penetration, accelerating the corrosion rate. Therefore, optimizing porosity within the coatings is crucial for enhancing the lifetime and CMAS resistance of TBCs.