等离子喷涂La2(Zr0.7Ce0.3)2O7热障涂层的抗热震性能

采用等离子喷涂制备了La₂(Zr_0.7Ce_0.3)₂O₇（LZ7C3）热障涂层,并对涂层的微观组织、相结构、成分、相稳定性、涂层热导率以及抗热震性能进行了研究.结果表明,LZ7C3涂层由单相烧绿石结构物质组成,高温稳定性较好;涂层的热导率较块材下降约20%,这是由于涂层具有较高的孔隙率所致:涂层在不同温度范围的热震寿命和失效机制不同,在室温至约1000℃间的热震寿命为116 cyc,涂层失效方式以片状剥落为主:在室温至1100℃间的热震寿命为53 cyc,涂层失效方式为片状剥落和层状撕裂;在室温至1200℃间的热震寿命为3 cyc,涂层失效方式以层状撕裂为主.

THERMAL SHOCK RESISTANCE OF La2(Zr0.7Ce0.3)2O7 THERMAL BARRIER COATING PREPARED BY ATMOSPHERIC PLASMA SPRAYING

Thermal barrier coatings（TBCs） are widely used in turbine engines to protect hot-section metallic components from corrosion and oxidation.The typical material of TBCs is 8YSZ due to its low thermal conductivity(2.1 W·m^-1·K^-1) and relatively high thermal expansion coefficient (1.1×10^-5 K^-1).However,at temperature above 1200℃,it could hardly be used for long-term application for its low sintering resistance and low phase stability.So it is urgently needed to develop novel TBCs materials with higher phase stability and lower thermal conductivity than 8YSZ.Recently, some materials have been evaluated as the candidates for TBCs,such as LaMgAl₁₁O₁₇（LMA）, La₂Zr₂O₇（LZ）,La₂Ce₂O₇（LC） and La₂(Zr_0.7Ce_0.3)₂O₇（LZ7C3）.Among those interesting candidates, the LZ7C3 ceramic shows the promising thermophysical properties for high-temperature TBCs.In this paper,the novel thermal barrier LZ7C3 coating was prepared by atmospheric plasma spraying.The microstructure,phase structure,composition,phase stability,thermal conductivity and thermal shock behavior of LZ7C3 coating were studied.These results show that the coating had single pyrochlore structure with high phase stability in high temperature.The thermal conductivity of coating is 20% lower than the bulk material due to high porosity of coating.The thermal shock tests indicate that the lifetime and failure mechanism depend on the test temperature.The coatings are failed after 116 cyc thermal shock from 1000℃to room temrature.which is attributed to the spallation of lamella.The failure mode of lamella spallation and layer fracture are found when the coating tested at 1100℃, the thermal shock lifetime is 53 cyc.Whereas at 1200℃,the coatings are spalled entirely after 3 cyc thermal shock in the way of layer fractur at the interface between LZ7C3 and bond coat.