单晶高温合金雀斑研究进展

Research progress in freckles of single crystal superalloys

为满足先进航空发动机发展需求,航空发动机涡轮叶片的结构日趋复杂,并且作为涡轮叶片首选材料的单晶高温合金中高熔点合金元素含量不断增加,由此导致单晶高温合金涡轮叶片制备过程中结晶缺陷形成倾向增大,直接影响单晶涡轮叶片的质量。本文以单晶高温合金定向凝固过程中出现的一种晶体缺陷——雀斑为讨论对象,综述了近年来雀斑形成机制、判据模型及其控制方法相关研究工作,分析了合金成分、叶片结构、定向凝固工艺和结晶取向对雀斑形成机制的影响,指出考虑不同合金体系中的合金元素与定向凝固过程的参数对雀斑形成的影响,进一步研究复杂结构单晶涡轮叶片雀斑形成规律,建立雀斑预测与控制的有效方法是未来的研究方向。

To meet the development needs of advanced aeroengines,the structure of aeroengine turbine blades is becoming increasingly complex,and the content of refractory elements is increasing in single crystal superalloys,which are the preferred materials for turbine blades.As a result,the tendency to form the grain defects increases during the preparation of single crystal turbine blades,which directly affects the quality of single crystal turbine blades.In this paper,a kind of grain defect that appears in the directional solidification process of single crystal superalloys—freckle was discussed.The research works on the formation mechanism,the criterion model and the control method of freckles formation during the directional solidification of single crystal superalloys in recent years was reviewed.The influence of the alloy composition,blade structure,directional solidification process and crystal orientation of single crystal castings on the formation of freckles was analyzed.Considering the influence of the alloying elements in different alloy systems and the parameters of the directional solidification process on the freckle formation,further studying the freckle formation mechanism of the single crystal turbine blade with complex structures,establishing an effective method for prediction and control of freckles are the future research directions.