原位冶金制备YSZ/Zr/NiCrAlY连续梯度耐高温涂层及热应力失效机制研究

The spalling failure of the thermal barrier coatings (TBCs), induced by the thermal stresses and thermal grown oxide (TGO) layer of micro-crack under thermal cycling, is one of the most urgent problems to be solved..In this study, in-situ metallurgy growth YSZ/Zr/NiCrAlY continuous gradient TBCs was prepared on the surface of nickel-base alloy by double glow plasma surface metallurgy technology. The in-situ metallurgy growth mechanism of the TBCs was obtained. The effect of continuous gradient TBCs on thermal stress and thermal stability was studied by controlling the growth mechanism of the coating, and the effect of the coating on the oxidation mechanism of metallic bond coat was also investigated. The physical properties model of continuous gradient thermal barrier coatings was established, by study of microstructure and composition of coatings. Then, the finite element analysis was performed to calculate the distribution of the temperature field and residual stress, and the failure modes and failure positions are analyzed. The formation and evolution mechanism of TGO layer in TBCs during high temperature thermal cycling was studied, which has important research significance both in the applications of TBCs in future aerospace and the development and research of novel TBCs.

在热循环工作条件下，热障涂层内部热应力和热生长氧化（TGO）层的微裂纹扩展导致的剥落失效是当前热障涂层所面临的最迫切的难题之一。.本课题拟采用双辉等离子表面冶金技术在镍基合金表面获得原位冶金生长的YSZ/Zr/NiCrAlY连续梯度热障涂层，提出热障涂层的原位冶金生长机制。通过连续梯度热障涂层生长机制的调控，研究该涂层对内部热应力及热稳定性的影响，探讨其在抑制金属粘结层氧化时的作用机理。通过对该热障涂层的组织成分的研究，建立连续梯度热障涂层的物性模型，利用有限元方法计算涂层内部温度场和残余应力的分布状态，分析涂层失效机制。揭示这种连续梯度热障涂层中TGO层在高温热循环下的形成和演化机制，对解决未来航空发动机在耐热涂层方面的应用及新型高温涂层的开发与研究具有重要的研究意义。

发动机热端零部件的热障涂层的残余热应力和热生长氧化（TGO）层的微裂纹扩展导致的剥落失效是目前热障涂层中普遍存在的问题。本项目基于对热障涂层的失效形式进行了实验研究和理论分析，提出连续梯度的新型热障涂层结构。新型的连续梯度热障涂层采用双辉等离子表面冶金技术，成功地在NiCrAlY粘结层表面原位反应制得梯度ZrO2陶瓷层，实现了YSZ/Zr/NiCrAlY涂层结构组织成分的连续梯度变化，降低了陶瓷层/金属粘接层/镍基合金的界面之间的热膨胀系数差异，减小涂层残余热应力。通过研究工艺对涂层组织结构的影响规律，揭示了连续梯度陶瓷层的形成机理，获得了连续梯度陶瓷层的显微组织结构对性能的影响规律。研究了ZrO2/Zr/NiCrAlY连续梯度陶瓷层的氧化层形成机理，揭示了该涂层在高温环境下对基体材料的氧化防护机制。氧化实验结果表明，在高温氧化条件下，连续梯度陶瓷层没有出现氧化剥落现象，氧化100h后的氧化增重仅为基材Inconel 718合金的27.9%，其氧化膜为致密的ZrO2和Cr2O3膜层，没有明显的孔洞和裂纹。研究了在高温氧化环境下，氧元素在ZrO2/Zr/NiCrAlY连续梯度陶瓷层中的扩散机制，并分析涂层内部氧化产物形成机理。基于面向对象有限元分析方法，研究涂层结构、氧化产物及温度场对涂层热应力的影响规律，发现在涂层界面处未发现热应力集中现象，残余热应力主要集中在粗糙的涂层表面。研究了ZrO2/Zr/NiCrAlY连续梯度陶瓷层的摩擦磨损行为，发现涂层的主要磨损机制为磨粒磨损和少量粘着磨损，涂层比磨损率较基材降低了77.5%，明显改善了基体的耐磨性能。