Corrosion resistance evaluation of thermal barrier coatings using sol–gel-derived CMAS sol-precursor mixture

Thermal barrier coatings (TBCs) protect gas turbine components from high-temperature environments. However, molten calcium magnesium aluminosilicate (CMAS), formed from ingested debris during operation, can infiltrate TBCs and cause failure. In this study, a CMAS sol-precursor mixture was synthesized via a sol–gel method by combining SiO₂ sol with chloride-based precursors under controlled pH conditions. The resulting CMAS sol-precursor mixture, in slurry form, was uniformly and quantitatively coated on freestanding yttria-stabilized zirconia (YSZ) specimens. After coating, the specimens underwent high-temperature heat treatment to simulate CMAS-induced corrosion. After high-temperature treatment, microstructural and phase analyses revealed that CMAS infiltration increased with longer heat treatment and greater coating amounts. This infiltration caused a reduction in porosity and a phase transformation from tetragonal to monoclinic YSZ. These results demonstrate that the synthesized CMAS sol-precursor mixture enables reliable and precise evaluation of CMAS corrosion in TBCs and offers an effective method for reproducing degradation behavior under controlled conditions.