Study on the ablation resistance of plasma sprayed La2(Zr0·7Ce0.3)2O7/YSZ and La1·9Ca0·1(Zr0·7Ce0.3)1.9Cr0·1O6.9/YSZ thermal protection coatings

Abstract

Metal materials have been widely used in hypersonic aircrafts due to their unique advantages, while none of the alloys can withstand the extreme aerodynamic thermal environment without ablation failure. Thermal protection coatings with low thermal conductivity or high infrared radiation are usually used to prevent heat from entering metal matrix, and at the same time, prolong or avoid the occurrence of ablation failure. Our previous study has shown that co-doping of Ca2+ and Cr3+ ions could effectively improve the infrared radiation performance of La2(Zr0·7Ce0.3)2O7(LZ7C3) ceramic. In this paper, plasma spraying method was adopted to prepare LZ7C3/YSZ and La1·9Ca0·1(Zr0·7Ce0.3)1.9Cr0·1O6.9(LZ7C3Cr)/YSZ coatings on steel substrate, and the anti-ablation and thermal protection performance evaluation experiment were carried out with oxyacetylene flame. The results showed that the LZ7C3/YSZ coating could protect the steel substrate from ablation damage with ablation surface temperature of 1650 °C and ablation time of 300 s. Under the same evaluation condition, the LZ7C3Cr/YSZ coating showed better ablation resistance than the LZ7C3/YSZ coating to some extent, the reason for this was that LZ7C3Cr/YSZ coating could reduce the ablation surface temperature by 100 °C due to the high infrared radiation performance, and LZ7C3Cr material had higher thermal expansion coefficient than LZ7C3 material, which led to lower thermal mismatch stress between the coating and the metal matrix in the ablation process. In addition, the formation of surface vertical microcracks on LZ7C3Cr/YSZ coating during the ablation process also played an important role in the improvement of ablation resistance of LZ7C3Cr/YSZ coating.