In this study, the effects of Co content on the microstructure and Charpy impact properties of Fe-Cr-W ferritic/martensitic oxide dispersion strengthened (F/M ODS) steels are investigated. F/M ODS steels with 0–5 wt% Co are fabricated by mechanical alloying, followed by hot isostatic pressing, hot-rolling, and normalizing/tempering heat treatment. All the steels commonly exhibit two-phase microstructures consisting of ferrite and tempered martensite. The volume fraction of ferrite increases with the increase in the Co content, since the Co element considerably lowers the hardenability of the F/M ODS steel. Despite the lowest volume fraction of tempered martensite, the F/M ODS steel with 5 wt% Co shows the highest micro-Vickers hardness, owing to the solid solution-hardening effect of the alloyed Co. The high hardness of the steel improves the resistance to fracture initiation, thereby resulting in the enhanced fracture initiation energy in a Charpy impact test at – 40oC. Furthermore, the addition of Co suppresses the formation of coarse oxide inclusions in the F/M ODS steel, while simultaneously providing a high resistance to fracture propagation. Owing to these combined effects of Co, the Charpy impact energy of the F/M ODS steel increases gradually with the increase in the Co content.

Abstract
1. 서 론
2. 실험방법
3. 실험결과 및 고찰
4. 결 론
References

• 권대현(울산대학교 중공업융합기술공학과) | Daehyun Kwon (Department of Convergence Technology for Heavy Industries, University of Ulsan)
• 노상훈(한국원자력연구원 신소재융합기술연구부) | Sanghoon Noh (Nuclear Materials Division, Korea Atomic Energy Research Institute (KAERI))
• 이정구(울산대학교 중공업융합기술공학과, 울산대학교 첨단소재공학부) | Jung Gu Lee (Department of Convergence Technology for Heavy Industries, University of Ulsan/School of Materials Science and Engineering, University of Ulsan) Corresponding Author