In the present study, yttria-partially-stabilized zirconia (YSZ)/Al 2 O 3 coatings, which are used for jet engines, gas turbines and diesel engines were coated with thermal barrier coatings (TBCs) 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 coatings were produced using a METCO 3MB plasma spray gun on stainless steel and graphite substrates. Scanning electron microscopy (SEM) was used to analyze the microstructures of the coated samples. 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. The presence of alumina phase commonly improves the mechanical properties of YSZ.

Thermal barrier coatings (TBCs) were deposited by an Air Plasma Spraying (APS) technique. The coating comprised of YSZ – 0, 20, 50 and 80 wt % Al 2 O 3 ; NiCrAlY bond coat; and AISI 304L stainless steels substrate. Thermal shock tests were performed over the specimens, at 1000 °C and 1200 °C for 5 min and then forced air quenching. The samples were directly pushed into a tube furnace at 1000 °C and 1200 °C. The results were prominent in forced air quenching tests at 1000 °C , where the lives of the TBCs were observed more than 66 cycles. It was noticed that with increase of Al 2 O 3 content the thermal shock life of the specimens decreased. Further, the coating roughness decreased by Al 2 O 3 addition. It was observed that with decrease in coating roughness, the thermal shock life decreased slightly.