Thermal cycle properties of plasma sprayed YSZ/Al 2 O 3 thermal barrier coatings

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°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.