重型燃气轮机高温透平叶片热障涂层系统中的应力和裂纹问题研究进展

The Stresses and Cracks in Thermal Barrier Coating System:A Review

燃气轮机是清洁高效火电能源系统的核心动力装备之一,是关乎国家能源安全和国防安全的战略高技术,是国家重大装备制造水平的标志,被誉为制造业王冠上的明珠.透平前燃气温度代表了燃气轮机的技术水平,人们一直在不断地追求燃气温度的提高.目前,国际最先进的重型燃气轮机的透平前燃气温度已达1600℃,未来还将向1700℃及以上发展.这种极端高温服役环境对高温透平叶片的设计和制造提出了严峻挑战,热障涂层(TBC)技术是解决这一问题的核心技术之一,在燃气轮机发展进程中发挥了重要作用,它不仅具有热障效果,而且还能防止氧化、腐蚀、外来物冲蚀等对叶片造成的损伤.因此,深入研究TBC的失效机理及其影响因素,对TBC的设计、制备及强度评价具有重要意义,对燃气轮机的安全服役具有重要作用.本文拟介绍重型燃气轮机高温透平叶片TBC系统中应力和裂纹问题的国内外最新研究进展,重点介绍本课题组十年来的研究成果,涉及理论、实验和数值分析几个方面.主要内容包括:TBC制备过程中的热应力,热生长氧化物(TGO)及其诱发的生长应力,TBC中的表面裂纹、界面裂纹及表界面裂纹间的竞争,TBC双轴强度评价方法,先进层级TBC中的表面和界面裂纹及其竞争,表面环境沉积物(CMAS)渗入诱发的涂层脱粘行为,陶瓷层烧结及其对TBC开裂的影响等.

Gas turbine is a class of clear and efficient power and energy machines, which has wide ap- plications to air engine, power generation, chemical and oil engineering, etc. The manufacture of gas tur- bine is a mark of the manufacturing capability of a nation and is regarded as a pearl on the crown of manu- facturing technology. Advanced gas turbines are featured by the high inlet gas temperature, as well as its continuous increase due to its key role in the turbine performance. The current inlet temperature of the ad- vanced gas turbine has reached 1600℃ and is expected to be 1700℃ and much higher in the future. It is challenging to design and manufacture the high-temperature turbine blades working in such an extreme temperature environment. Thermal barrier coating system （TBCs） is one of the core technologies for the design and manufacturing of advanced gas turbines and has been playing important roles in the development history of gas turbines. TBCs can increase the inlet temperature and protect the turbine blades from oxidation, corrosion, foreign object impact, particle erosion and so on. Therefore, thorough investigations on the failure mechanisms and the influence factors of TBCs are crucial to the design, manufacturing and strength assessment of TBCs and furthermore ensure the safe service of gas turbines. In this review arti- cle, we present the more recent advances in the studies on stresses and cracks in TBCs of gas turbine blades, including theoretical, experimental and numerical analyses. This paper covers the failure modes in TBC, the thermal stresses generated in the fabrication of TBC, the thermally grown oxide （TGO） and its resulting growth stress, the surface cracks, interface cracks and their competition in TBCs, the evaluation method of biaxial strength of TBCs, the delamination induced by the penetration of environmental CaO- MgO-Al3O2-SiO2 （CMAS） into coatings, and the sintering effect on the cracking of ceramic layer. Finally, potential directions for further research are concluded.