Oxidation resistance and thermal cycling properties of thermal barrier coatings for DD90 single crystal superalloy

Abstract:

Thermal barrier coatings were deposited on the third generation single crystal superalloys DD90.NiCrAlY+NiCoCrAlTaY double-layer bond coatings were prepared by high velocity oxy-fuel spray (HVOF).The ceramic layers were YSZ and MSZ/YSZ structures which were prepared by using atmospheric plasma spray technique, respectively. The oxidation resistance test at 1150℃ shows that the weight gain of the YSZ coating is significantly higher than that of the MSZ coating. After 250 thermal cycles at 1200℃, the two coatings do not occur obvious phase transition and the sintering resistance of the MSZ coating is better. The TGO of the two coatings mainly consists of Al2O3 and a small amount of spinel structure mixed oxides. The double-layer bond layer reduces the diffusion of Al element into the substrate, while due to the concentration gradient diffusion of Cr element leads to the precipitation of topological close-packed (TCP) phases and the increase in the depth of secondary reaction zone (SRZ).