일방향 응고 CM247LC 초내열합금의 크리프 조건에서 표면 산화와 연계된 γ'-석출 고갈 지역 및 γ' 조대화

서지정보

ㆍ발행기관 : 한국재료학회 ㆍ수록지정보 : 한국재료학회지 / 33권 / 10호
ㆍ저자명 : 최병학, 최광수, 한성희, 김대현, 안종기, 강동수, 서성문

목차

1. 서 론
2. 실험 방법
3. 결과 및 고찰
3.1. 열처리(STD/MIN/MAX) 경도, 수지상 조직 및크리프 수명 비교
3.2. 열처리(STD/MIN/MAX) SEM 미세조직 및 Mapping/EDS 성분 분석 비교
3.3. 열처리 및 크리프에 의한 표면층 형성 기구 고찰
4. 결 론
Acknowledgement

영어 초록

This study used optical and scanning electron microscopy to analyze the surface oxidation phenomenon that accompanies a γ'-precipitate free zone in a directional solidified CM247LC high temperature creep specimen. Surface oxidation occurs on nickel-based superalloy gas turbine blades due to high temperature during use. Among the superalloy components, Al and Cr are greatly affected by diffusion and movement, and Al is a major component of the surface oxidation products. This out-diffusion of Al was accompanied by γ' (Ni3Al) deficiency in the matrix, and formed a γ'-precipitate free zone at the boundary of the surface oxide layer. Among the components of CM247LC, Cr and Al related to surface oxidation consist of 8 % and 5.6 %, respectively. When Al, the main component of the γ' precipitation phase, diffused out to the surface, a high content of Cr was observed in these PFZs. This is because the PFZ is made of a high Cr γ phase. Surface oxidation of DS CM247LC was observed in high temperature creep specimens, and γ'-rafting occurred due to stress applied to the creep specimens. However, the stress states applied to the grip and gauge length of the creep specimen were different, and accordingly, different γ'-rafting patterns were observed. Such surface oxidation and PFZ and γ'-rafting are shown to affect CM247LC creep lifetime. Mapping the microstructure and composition of major components such as Al and Cr and their role in surface oxidation, revealed in this study, will be utilized in the development of alloys to improve creep life.

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