Thermal cycle properties of plasma sprayed YSZ/Al2O3 thermal barrier coatings

Abstract

In the present study, yttria partially stabilised zirconia (YSZ)/Al2O3 coatings, which are used for jet engines, gas turbines and diesel engines were coated with thermal barrier coatings to provide high thermal resistance, reduce the metal surface temperatures and increase component durability. The effect of alumina addition from 0 to 80 wt-% on the properties of plasma sprayed YSZ coatings was investigated. The coating comprised of YSZ-Al2O3 (0, 20, 50 and 80 wt-% Al2O3); NiCrAlY bond coat; and AISI 304L stainless steels substrates. Scanning electron microscopy was used to analyse the microstructures of the coated samples. Thermal shock tests were performed over the specimens, at 1000 and 1200 degrees C for 5 min and then forced air quenching for 2 min. The microhardness was investigated depending on the alumina contents. Vickers hardness on cross-section of coatings was observed to increase with the increase in alumina mixing ratio. It was noticed that with increase in Al2O3 content the thermal shock life of the specimens decreased.