DD6单晶涡轮叶片缘板裂纹与再结晶研究

针对DD6单晶涡轮叶片在试车后缘板出现裂纹的现象,通过裂纹外观检查、断口形貌观察、显微组织及化学成分分析等工作,开展基于裂纹特征的缘板失效模式研究.研究结果表明:DD6单晶涡轮叶片缘板裂纹是由表面再结晶导致的疲劳开裂,其形成与存在富钨白色析出相的枝晶界面有直接关系;在试验条件下裂纹沿富钨(W)的白色颗粒链扩展,并沿界面延伸,导致疲劳失效.同时,发现缘板表面再结晶在叶片使用之前已存在,是缘板凝固区域因过大铸造热应力而形成碳化物,进而在热处理过程形成晶界富钨白色析出相的再结晶晶粒.

Platform crack and recrystallization of DD6 single crystal turbine blade

It was found that the cracks appeared on the surface of DD6 single crystal turbine blade platform after testing.Based on the cracks character,the platform failure mode was studied by appearance check,observation on fracture surfaces,microscopic structure examination,and chemical analysis.The results show that the cracks have made from the surface recrystallization of DD6 single crystal turbine blade platform;it has relation to the grain boundary face.Under stress condition,the cracks have expensed along the white particles bond until fatigue failure.Meanwhile,it was found that the recrystallization zone already exists at its surface before application.Owing to the larger cast stress during cast process,the carbide is formatted in platform zone.Then,the recrystallization grain,which mass precipitated phases with W element are around its boundary,is formatted in heat treatment.