基于微应变的热障涂层/高温合金力学行为原位表征及失效机制研究

Severe interdiffusion bahavior occurs for thermal barrier coatings/superalloy system during service, resuliting in affecting the nature properties of the coatings and superalloys, and then degrading the service life. The physical-chemistrial nature and failure mechanism of interface of the TBCs coated blade under the engine condiction become a "bottleneck" for the application of TBCs. The basic scientific problem is burning question. The interfacial interdiffusion behavior between YSZ/MCrAlY TBCs and directionally solidified and/or single crystal Ni-based superalloy, chemical composition, structure and the physical property parameters of the phase during exposed in high temperature are investigated in this project. The mechanical behavior of the multi-interfacial YSZ/TGO/BC/IDZ/substrate system, forming after oxidaton and interdiffusion, is carried out by in situ tensile test with micro-strain testing technology. And the influence rule of the interfacial stress and its distribution for the muti-interfacial coating/superalloy system influenced by the interfacial evolution and the strain of the coated superalloy are studying. The mechanism of crack initiation, propagation and fracture failure of the coated superalloy is understood. This is of scientific guidance significance to characterize the failure model, mechanism and life prediction for the TBCs coated superalloys.

热障涂层/高温合金体系在服役条件下发生严重的互扩散行为，影响涂层和合金的特有性能，降低其使用寿命。叶片热障涂层在发动机环境下界面的物理化学本质和失效机理等问题已成为影响我国叶片热障涂层应用的"瓶颈"，其基础科学问题亟待解决。本项目旨在研究高温下热障涂层YSZ/MCrAlY与定向凝固/单晶镍基高温合金的界面互扩散行为、结构、化学成分、组织及其物理性能参量等，采用微应变法通过原位拉伸试验研究经氧化扩散后具有多个界面的陶瓷层/TGO/粘结层/互扩散层/基体合金体系的力学行为，探索界面演变和带涂层合金的应力应变对多界面涂层/合金体系的界面应力及其分布的影响规律，掌握涂层/合金体系的界面裂纹萌生、扩展和断裂失效机制，对于明确热障涂层/高温合金体系的失效模式、机理和预测寿命，优化设计并提高热障涂层/高温合金的服役寿命具有重要的科学指导意义。

热障涂层/高温合金体系在服役条件下发生严重的元素互扩散行为，影响涂层和合金的特有性能和使用寿命及安全可靠性，叶片热障涂层界面的物理化学本质和失效机理等问题已成为影响叶片热障涂层应用的“瓶颈”。本项目研究高温下YSZ/CoCrAlY与DZ125的界面元素扩散互扩散行为，分析了元素扩散对热障涂层体系组织演变的影响机制，建立了相应的扩散模型并采用Boltzmann-matano图解法理论计算了Co、Ni、Al元素的互扩散系数，及其对组织与力学性能影响、裂纹萌生、扩展、断裂等失效模式与机制。. 研究结果表明，元素互扩散导致CoCrAlY涂层的β-CoAl相演变为β-CoNiAl相和γ-CoNi相。基体表层的互扩散区（IDZ）由γ/γ`相变为富含Al的β-NiCoAl相与γ-CoNi相。二次反应区（SRZ）由富含W、Mo、Cr元素的TCP相和γ/γ`相组成。涂层组织转变对涂层的残余应力有重要影响。涂层和基体的硬度、弹性模量等也发生变化。.真空下元素扩散均比其在大气下的快（约2倍），Co、Ni的扩散速率均比Al的大一个数量级。. 拉应力作用下涂层裂纹形成与扩展过程可分为五个阶段.热暴露热障涂层的饱和裂纹密度为7.55~13.40 /mm，显著大于沉积态的2.95 /mm。. 经热暴露后热障涂层陶瓷层残余应力由沉积态的拉应力状态（29.91 MPa）转变为压应力状态，且随热暴露时间延长残余压应力增加，从-134.53 MPa到-314.27 MPa变化。粘结层/TGO圆弧凸起界面产生应力集中，在陶瓷层内形成较大的应力，导致裂纹和陶瓷层垂直裂纹的失效形式。