Microstructural approach for comparative study of two conventional thermal barrier coatings: Hot corrosion and cyclic oxidation

Thermal barrier coatings (TBCs) are critical for protecting Ni-based superalloys in gas turbine hot sections, yet comparative studies of alumina, YSZ, and MSZ under identical cyclic oxidation and hot corrosion conditions remain scarce. This work systematically evaluates flame-sprayed alumina, YSZ, and MSZ top coats on IN738LC with NiCrAlY bond coat, subjected to 900 °C cyclic oxidation (20-h cycles) and Na 2 SO 4 hot corrosion (120 h). Experimental methods include controlled flame-spray deposition, continuous weight-change monitoring, XRD phase analysis, and FESEM-EDS microstructural characterization. Key quantitative results: alumina failed within 20 h under both tests; YSZ and MSZ survived 120 h cyclic oxidation, but MSZ demonstrated 76 % superior hot-corrosion resistance than YSZ, attributed to lower MgO reactivity and reduced phase-transformation stress. The highlight is the direct, quantitative demonstration of MSZ’s superior hot-corrosion resistance under realistic service-like conditions, establishing MSZ as a promising alternative for turbine components exposed to low-quality fuels. These findings provide actionable guidance for coating selection in industrial and aerospace applications.