Investigation of the effect of calcium-alumina-magnesium-silicate (CMAS) infiltration on the microstructural characteristics of thermal barrier coatings (TBCs)

Thermal barrier coatings (TBCs) are protective coating systems that are mostly used to improve the thermal insulation and functional performance of gas turbine engines and stable and moving components of aircrafts. These coatings protect underlying materials against structural failures under various severe conditions occurring under high temperatures such as corrosion, oxidation, CaO-MgO-Al2O3-SiO2 (CMAS), thermal shock/cycle, volcanic ash, and vermiculite deposits. In this study, CoNiCrAlY metallic bond coats were deposited onto Inconel 718 superalloy using high-velocity oxygen fuel (HVOF) deposition technique. Afterwards, ZrO2+%6-8Y2O3 (YSZ) based ceramic top coatings were fabricated onto the bond coats using the electron beam physical vapor deposition (EB-PVD) technique. The produced TBC samples were subjected to vermiculite (VM) deposition at 1225℃ for a period of 4 hours and then the characterization of the coatings was performed. X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer elemental mapping analysis (EDS), stereo microscopy analyses, as well as porosity and hardness measurements were performed to determine the phase structures, microstructural and mechanical properties of the TBCs. The obtained results were comparatively evaluated with the recent related studies in the literature.