Effect of Aging Time at High Temperature on Microstructural Evolution Behavior of a Nickel-Based Single Crystal Superalloy

摘要:

研究了高温时效对一种镍基单晶高温合金组织演变行为的影响。使合金在980, 1050, 1100 ℃，进行20, 50, 100 h的短期时效及在1100 ℃下进行200~800 h的长期时效，采用扫描电子显微镜进行组织形貌的观察、电子探针显微分析仪分析TCP相的成分，并对时效后的试样进行硬度测试。试验结果表明：在短期时效时，γ'相的粗化符合扩散控制理论的长大规律，即r3与t成正比，可求得不同温度的粗化长大系数；在长期时效下，1100 ℃时效400 h后，筏排状的γ'相形成且有TCP相析出，TCP相中富含Re和W元素；此外，在1050 ℃时效50 h及在1100 ℃时效20和100 h后，合金中也有TCP相的析出；硬度结果显示，不同时效条件的试样硬度值没有明显变化

Abstract:

The microstructural evolution behavior of one kind of nickel-based single crystal superalloy aged at elevated temperature was investigated. The short-term exposures were performed at 980, 1050 and 1100 oC for 20, 50 and 100 h, and long time agings were carried on from 200 to 800 h at 1100 oC. Microstructure observation was carried out by field emission scanning electron microscope (FE-SEM). Electron Probe Micro Analyzer (EPMA) was employed to determine the composition of TCP phase. The microhardness was tested to all the aged specimens. The results show that in short-term aging, the coarsening of γ' particles in this superalloy follows the standard r3-t kinetics of diffusion-controlled particle growth and coarsening rate constants were calculated. During long-term aging, for samples exposed for 400 h at 1100 oC, the rafted structure has developed completely and TCP precipitates has formed. The composition of TCP phase is mainly composed of Re and W. In addition, under some conditions of short time aging, TCP phases are found to precipitate from the alloy. The microhardnesses of all the aged specimens exhibit no obvious changes