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.

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

• 최병학(강릉원주대학교 신소재금속공학과) | Byung Hak Choe (Department of Metal and Materials Engineering, Gangneung-Wonju National University, Gangneung 25457, Republic of Korea) Corresponding author
• 최광수(국립과학수사연구원 서울과학수사연구소) | Kwang Soo Choi (Engineering Division, National Forensic Service Seoul Institute, Seoul 08036, Republic of Korea)
• 한성희(강릉원주대학교 신소재금속공학과) | Sung Hee Han (Department of Metal and Materials Engineering, Gangneung-Wonju National University, Gangneung 25457, Republic of Korea)
• 김대현(강릉원주대학교 신소재금속공학과) | Dae Hyun Kim (Department of Metal and Materials Engineering, Gangneung-Wonju National University, Gangneung 25457, Republic of Korea)
• 안종기(한화에어로스페이스 항공소재연구센터) | Jong Kee Ahn (Aerospace R&D Center, Hanwha Aerospace, Sungnam 13488, Republic of Korea)
• 강동수(한화에어로스페이스 항공소재연구센터) | Dong Su Kang (Aerospace R&D Center, Hanwha Aerospace, Sungnam 13488, Republic of Korea)
• 서성문(한국재료연구원 고온재료연구실) | Seong-Moon Seo (Department of High Temperature Materials, Korea Institute of Materials Science, Changwon 51508, Republic of Korea)