Influence of original powders on the microstructure and properties of thermal barrier coatings deposited by supersonic atmospheric plasma spraying, part II: Properties

In this paper, the thermal shock resistance, oxidation resistance and thermal insulation performance of “conventional” microsized and nanostructured coatings (named as MC and NC respectively) deposited by supersonic atmospheric plasma spraying (SAPS) were investigated. The results showed that due to the improvement of intersplat cohesion and bonding strength between the top coat and bond coat, the MC presented a higher thermal shock resistance, which was distinct from the previous reports about the property difference between the conventional and nanostructured coatings. In addition, the result from isothermal oxidation test indicated that the oxidation kinetics of both coatings followed a parabolic law. The weight gain of MC was slightly lower than that of NC before 600 h at 1100 °C. However, due to the formation of vertical cracks which penetrated the whole top coat, the weight gain for MC after 1000 h was slightly higher than that of NC, indicating that the NC had a higher oxidation resistance after long time exposure. Meantime, because lots of fine cracks were formed between the unmelted particles and lamellar structures, the temperature drop (ΔT) of NC increased with the increase of testing times. The nanostructured SAPS-coating showed better oxidation resistance and thermal insulation properties, but the inter-splat cohesion and top coat/ bond coat interface adhesion are still needed to be improved in order to increase its thermal cycling life.