单晶叶片表层组织转变影响因素及其控制方法

Influencing factors and control methods of surface microstructure transformation of single crystal blade

针对单晶叶片铸件在高温热处理后,极易在结构畸变区域发生结构再结晶问题,本研究提出了一种基于单晶再结晶临界应力特性的叶片结构残余应力控制方法,旨在通过研究单晶合金再结晶的临界应力特性,并结合结构细节优化设计方法,将叶片结构残余应力水平控制在单晶再结晶临界应力的安全区域内。结果表明:诱发单晶叶片结构再结晶的两大因素是温度和应力集中水平,再结晶起源于不连续的胞状组织,且发生单晶再结晶时的临界应力与叶片结构设计参数、热处理温度之间存在一定的函数关系,经真实叶片试验验证,证实该方法可实现单晶叶片结构完整性与表层组织连续性的控制,有效抑制单晶叶片表层组织的转变。

The problem of surface recrystallization was found on the structural distortion region of single crystal blade after the high temperature heat treating. To solve this problem, a method was proposed based on critical stress of recrystallization and residual stress of structure. With the help of structural optimization technology, the study showed that the critical stress happened justly under the recrystallization of the single crystal blade, and the residual stress level of structure was no more than the critical stress of recrystallization stress. Results showed that the temperature and stress concentration level were two major factors inducing structural recrystallization, and the recrystallization was originated from discontinuous cellular microstructure of the single crystal blade. Meanwhile, the critical stress of recrystallization was used to establish a relationship with the structure design parameters and the heat treatment temperature, then, the test validation work was completed for the real blade. This method is effective to restrain the structural recrystallization of single crystal blade and control the structural integrity and surface microstructure continuity.