22Cr-9Mo-3Fe-4Nb 니켈기 초내열합금의 저주기 피로에 따른 미세조직변화

• Published in: 대한금속·재료학회지, 55(9) Vol. 55; no. 9; pp. 609 - 614
• Main Authors: 송영석, Youngseok Song, 석진익, Jinik Suk, 강정윤, Chung Yun Kang
• Format: Journal Article
• Language: Korean
• Published: 대한금속재료학회 05.09.2017; 대한금속·재료학회
• Subjects: alloys; carbides; fatigue; forging; microstructure; transmission electron microscopy; 재료공학
• ISSN: 1738-8228; 2288-8241
• DOI: 10.3365/KJMM.2017.55.9.609

A new Ni based superalloy with high fatigue resistance and fine grain was considered as a material for high-pressure buckets in fossil fuel power plants. Since such buckets are usually exposed to extreme operating conditions, low cycle fatigue tests were conducted to understand the microstructure evolution of the material during cyclic fatigue under total strains of 0.8, 0.9, 1.0 and 1.2%, and temperatures of 566, 593, 621, 649 and 700 ℃. Microstructural analysis of fractured specimens was conducted using TEM, SEM and OM to observe changes in the γ″ morphology, carbides, and fracture mode. Based on the observations of microstructural changes and low cycle fatigue properties, it can be concluded that grain size had the dominant effect on low cycle fatigue properties, regardless of the size of the transformed carbides and precipitates in these alloy systems. (Received March 7, 2017; Accepted June 7, 2017)