| Title |
Formation of Sigma Phase and Microstructure Evoluation during High Temperature Stress-Rupture of Rene' 77 |
| Authors |
염종택(Jong Taek Yum) ; 이재현(Je Hyun Lee) ; 조창용(Chang Yong Jo) ; 김상식(Sang Shik Kim) ; 최승주(Seung Joo Choe) |
| Abstract |
The possibility of formation of the a phase in the Rene´ 77 superalloy, when exposed to high temperature: and under the applied stress, has been evaluated. The Phacomp calculations on the Rene´ 77 used in the present study indicates that an electron vacancy number of this alloy is 2.45, which is not immune to formation of the a phase. Among the four stress-rupture test conditions, the σ phase was observed when the sample was exposed at 871℃ under the applied stress of 276 ㎫. The shape of the σ phase observed in the present study was more-or-less close to blocky shape, and the detrimental effect on stress-rupture property of the Rene´ 77 was minimal. It was interesting to find that the fracture modes were different with stress conditions. While fracture initiated near the carbide in High stress condition, it appeared to grow near the grain boundary or triple point in low stress condition. |