目的 研究带有Ni-P/Al复合中间层的AZ91D镁合金表面氧化钇稳定氧化锆热障涂层（YSZ TBCs），在400 ℃水淬热震实验中的失效行为。方法 通过化学镀和等离子喷涂（APS）技术，在Mg合金表面制备带有Ni-P和Ni-P/Al中间层的NiCrAlY/YSZ TBCs。于400 ℃水淬热震试验中进行涂层样品的失效行为及机理研究。利用X-射线衍射仪（XRD）、能谱仪（EDS）及扫描电镜（SEM）等，分析带有Ni-P、Ni-P/Al中间层的YSZ TBCs的物相组成和热震失效前后的显微组织。结果 带有Ni-P中间层的YSZ TBCs在平均热冲击循环61次后，涂层表面积的60%发生剥落；带有Ni-P/Al复合中间层的YSZ TBCs在平均热冲击循环91次后，整片涂层从基体上剥落分离。微观形貌结果表明，在水淬过程中，水介质进入异种金属界面处，化学性质活泼的Mg合金基体和金属Al均发生电偶腐蚀且前者更甚。在400 ℃加热-水淬过程中，NiCrAlY粘结层和Mg合金基体由于热膨胀系数不同，层间的热应力不断积累并作用于中间层。在腐蚀应力和热应力共同作用下，Ni-P层和Al层发生断裂，涂层剥离失效。结论 Ni-P/Al复合中间层能有效提高镁合金基体抗氧化能力和抗腐蚀能力，且涂层内热应力明显减小，整个涂层表现出更好的热稳定性，热震寿命有所提高。

The work aims to investigate the failure mechanism of NiCrAlY/YSZ TBCs with a Ni-P/Al composite interlayer on the surface of AZ91D magnesium alloy in 400 ℃ water quenching thermal shock test. NiCrAlY/YSZ TBCs with Ni-P and Ni-P/Al interlayers were prepared on Mg alloy substrate with electroless plating and atmospheric plasma spraying (APS). The failure behavior and mechanism of prepared coating samples were investigated in 400 ℃ water quenching thermal shock test. The phase compositions and the microstructures of the two as-prepared samples before and after thermal shock test were analyzed by X-ray diffractometry (XRD), energy dispersive spectrometer (EDS) and scanning electron microscopy (SEM). After suffering thermal shock for 61 cycles, nearly 60% of upper coating in YSZ TBCs with Ni-P interlayer peeled off. By contrast, the whole upper coating in YSZ TBCs with Ni-P/Al interlayer flaked after 91 thermal shock cycles. The micro-morphologies indicated that the active Mg alloy suffered more severe galvanic corrosion than the aluminum layer as the water medium penetrated into the interface between heterogeneous metals during the water quenching process. Meanwhile, the thermal stresses caused by the mismatch thermal expansion coefficient (TEC) of NiCrAlY bond coating and Mg alloy constantly accumulated and acted on interlayer. The co-effect of corrosion stress and thermal stress induced the fracture of Ni-P and Ni-P/Al interlayer, which led to peeling and failure of coating. Ni-P/Al composite interlayer can effectively improve the oxidation resistance and corrosion resistance of magnesium alloy base, and the thermal stress in the coating is obviously reduced. The whole coating shows better thermal stability and thermal shock life is improved.