Fatigue Strength of Functionally Graded Thermal Barrier Ceramic Coatings Subjected to Thermal Cycling under Gradient Temperature

热障涂层和防护涂层等表面改性技术是开发下一代先进燃气轮机的关键技术。作为开发先进燃气轮机高性能涂层系统项目的一部分，本研究项目研究了表面改性的先进材料的高温强度。结果表明：(1)研制成功了一种能够模拟涡轮叶片工作状态的新型疲劳试验机。(2)对常规双层NFGM涂层试样和功能梯度材料（FGM）涂层试样进行热疲劳试验。研究了功能梯度热障涂层在热循环过程中的损伤过程。对女性生殖器官的热障功能退化也进行了验证。(3)通过真空热循环试验，定量评价了功能梯度热障涂层对陶瓷涂层材料热疲劳强度的影响。(4)研究了低温等离子喷涂M-Cr-Al-Y合金后ni基高温合金IN 738LC在高温真空条件下的疲劳断裂，并与基体合金IN 738LC进行了对比。利用扫描电镜内的循环加载段专用设备对疲劳裂纹的扩展过程进行了研究。重点研究了涂层内的疲劳裂纹扩展行为和mccraly合金体系的依赖性，以及界面附近的疲劳裂纹扩展行为。(5)研究了镀铝层对ni基高温合金高周疲劳强度的影响，并与镀铝层进行了对比。通过对铝化物涂层脆性开裂临界应变的测量，提出了一种与实验寿命相对应的合理估算方法。少

Surface modification techniques, such as thermal barrier coatings and protective coatings are key technology to develop next generation advanced gas turbines. As a part of program to develop the high performance coating systems for advanced gas turbines, the high temperature strength of the advanced materials with surface modifications has been studied in this research program. The conclusions obtained are summarized as follows :(1) A new fatigue test machine which can simulate the service condition of turbine blades and vanes was successfully produced.(2) Thermal fatigue tests of conventional two-layr NFGM coating specimens and a functionally gradient material (FGM) coating specimens were carried out. Damage process of the functionally graded thermal barrier coatings during the thermal cycling was qualified. The degradation of thermal barrier function of the FGM was also qualified.(3) The effect of the functionally graded thermal barrier coatings on the thermal fatigue strength of the … More advanced materials with ceramic coatings surface damage strength was quantitatively evaluated by the thermal cycling test in vacuum.(4) The fatigue fracture of the Ni-base superalloy, IN 738LC,coated with the so-called M-Cr-Al-Y alloys by low pressure plasma spraying was studied and clarified at high temperature in vacuum condition, compared with that of the substrate alloy, IN 738LC.The fatigue crack propagation process was also made clear from the investigation employing the special equipment with cyclic loading stages which fit within the scanning electron microscope. Special focus was paod on the fatigue crack growth behavior in the coated layr and the dependence of the MCrAlY alloy systems, as well as near the interface.(5) The effect of aluminide coating on the high-cycle fatigue strengths of Ni-base superalloys was clarified at room temperature and 800 ﾟC in vacuum, in comparison with those of the substrates. Based on the measurement of a critical strain above which brittle cracking appeared at the aluminide coating, a simple method which can provide a reasonable estimation corresponding with the experimental life, was proposed. Less