燃气涡轮叶片的服役损伤与修复

Service Induced Degradation and Rejuvenation of Gas Turbine Blades

涡轮叶片是燃气轮机最重要的热端部件之一。它长期在不均匀的温度场、应力场以及燃气腐蚀和高温氧化的环境下工作,面临着蠕变、低周疲劳和高温腐蚀等多种失效威胁。系统地研究涡轮叶片在服役过程中的组织损伤与性能退化规律是揭示其失效机理、探索适宜的恢复热处理工艺以延长涡轮叶片使用寿命的必然途径。对目前已有的涡轮叶片服役损伤研究进行了总结,同时结合本课题组对不同类型的涡轮叶片长期服役后(空中飞行时间:1 200 h～20 000 h)组织和性能损伤评估的研究结果,对存在的各种服役组织损伤形式进行了归类和介绍,主要包括涂层的退化、拓扑密排相(TCP)的析出、二次反应区(SRZ)的形成,γ'相的粗化与筏排化,碳化物的分解与析出,蠕变孔洞与裂纹的形成等。此外,还总结了前人研究的服役涡轮叶片性能退化规律以及恢复热处理工艺。热端部件服役损伤的研究对燃气轮机关键部件的寿命管理和安全服役具有重要的指导意义和经济意义。

Turbine blades are one of the most important hot section components in gas turbine systems. They are subjected to complex combination of inhomogenous stresses and temperature distribution as well as high temperature corrosion and oxidation environment, resulting in failures caused by creep, low cycle fatigue and high temperature corrosion/oxidation. In order to understand failure mechanisms and develop proper rejuvenation heattreatment to extend the life time of turbine blades, it is of great necessity to study the relationship between microstructure and mechanical property degradation of turbine blades during service. This paper is to review the previous studies associated with service induced degradation of turbine blades. Various kinds of typical microstructural degradations are also classified, combined with the investigation of microstructural degradation of different types of turbine blades in aeroengines by our group （service time in air：1 200~20 000 h, respectively）. The following microstructural degradation is included： surface coating degradation, precipitation of Topologically ClosePacked Phases （TCPs）, formation of second reaction zone （SRZ）, coarsening and rafting of γ′ phase, decomposition or precipitation of carbides, and initiation of creep cavities and cracks, etc. In addition, previous studies of mechanical property degradation and the rejuvenation heattreatment of turbine blades are also summarized. It is suggested that the investigation of the mechanism for the service induced degradation of hot section components is of great importance and economic significance for the life management and materials safety in gas turbines.