新型镍钴基变形高温合金的高温低周疲劳行为及失效机制研究

Turbine disk, which is made from Ni-base superalloy, is one of the most important components in aero-engine and gas turbine systems. Since the disk is subjected to repeated thermal and mechanical stresses during operations, evaluation of the fatigue damage and fracture behavior of turbine disk is critically important for aerospace and gas turbine industries and is of great academic interest for scientific research. Ni-Co-base superalloy, which currently has the highest heat resistance for cast and wrought Ni-base superalloys, can meet the critical demand for high performance alloy in advanced gas turbine systems and has attracted much attention for domestic researchers. However, the low cycle fatigue behavior and related deformation mechanism of Ni-Co-base alloys has not been understood well yet. The objective of this proposal is to study the high-temperature low cycle fatigue behavior and its failure mechanisms of a new Ni-Co-base superalloy. Deformation characters at typical operating temperatures of turbine disk are systemically summarized for this alloy and deformation mechanisms are qualitatively clarified by analyzing the microstructural evolution during fatigue. Fatigue crack initiation is examined and a mode will be established through analyzing the fatigue damage and crack initiation characteristics. The effects of temperature, strain amplitude and microstructure on low cycle fatigue behavior will be discussed. . This research will not only afford the experimental evidence for failure analysis, safety service and life prediction of novel Ni-Co-base superalloys, but will also provide theoretical guideline for development of alloys with high fatigue resistance, which are very significant for alloy practical applications and alloy design theoretical development.

航空发动机和工业燃气轮机的关键部件涡轮盘在服役过程中极易产生高温低周疲劳损伤导致断裂失效。镍钴基高温合金是目前国际上耐温能力最高的涡轮盘用铸造变形高温合金，可以满足国内先进燃机对高性能合金的迫切需求。国内虽有研究者对其进行跟踪研发，但尚未有对其高温低周疲劳行为研究的报道。本项目拟对一种镍钴基高温合金的低周疲劳行为及失效机制进行深入研究；通过系统实验，确立合金在典型服役条件下低周疲劳宏观循环应力-应变的响应规律；解析合金在低周疲劳循环中的位错组态及其演变规律，揭示合金疲劳损伤机理；通过考察载荷参数和微观组织对合金疲劳裂纹萌生行为的影响，阐明疲劳裂纹萌生的特点和规律，建立应变量--疲劳裂纹萌生--疲劳寿命之间的依存关系。本研究成果将为新型镍钴基高温合金的失效分析、安全使用和新一代变形高温合金的设计研制提供技术基础和理论依据。

航空发动机和工业燃气轮机的关键部件涡轮盘高温合金在高温高速运转中容易产生疲劳损伤导致断裂失效，而低周疲劳损伤是最主要的失效模式。国家自然科学基金青年项目“新型镍钴基变形高温合金的高温低周疲劳行为及失效机制研究”采取力学与材料学相结合的手段，围绕新型镍钴基变形高温合金的高温低周疲劳损伤机理和裂纹萌生模式这一关键科学问题，对合金的低周疲劳行为进行了较为深入的研究。经过3年的努力，确立了新型镍钴基变形高温合金在典型服役条件下低周疲劳宏观循环应力-应变的响应规律，解析了合金在低周疲劳循环中的位错组态及其演变规律，揭示了合金疲劳损伤机理，建立了应变量--疲劳裂纹萌生--疲劳寿命之间的依存关系。同时也研究了一种新型镍基高温合金的高温组织稳定性和拉伸、蠕变等力学性能，解析了合金在多种条件下的微观变形机理。本项目揭示了高温低周疲劳变形机制与断裂机理，为新型变形高温合金在飞机发动机系统中的进一步工程应用提供了可靠的理论依据，同时为新一代变形高温合金的设计研制提供了重要技术基础。本项目共发表论文11篇，其中SCI收录10篇，EI收录1篇。参加国内外学术报告5人次，培养研究生2名。