25Cr-7Ni-2Mo-4W 슈퍼 2상 스테인리스강의 충격인성에 미치는 χ상의 영향

• Published in: Han-guk haeyang gonghak hoeji (Online) Vol. 27; no. 2; pp. 75 - 79
• Main Authors: 남궁원(Won Namgung), 강창룡(Chang-Yong Kang)
• Format: Journal Article
• Language: Korean
• Published: 한국해양공학회 2013
• Subjects: 해양공학; Impact toughness 충격인성; Super duplex stainless stee 슈퍼 2상 스테인리스강; χ phase χ상; W substitution W치환; Aging treatment 시효처리; chi; 2; W
• ISSN: 1225-0767; 2287-6715

This study was carried out to investigate the precipitation behavior of the ${\chi}$ phase and the impact toughness of 25%Cr-7%Ni-2%Mo-4%W super duplex stainless steel. The ${\chi}$ phase was precipitated in the early stage of aging, and with the increasing aging time. However, after reaching a maximum value, the number decreased as a result of the gradual transformation of the ${\chi}$ phase into the ${\sigma}$-phase. It was proved that the ${\chi}$ phase was an intermetallic compound, which represented a lower nickel concentration, higher chromium and molybdenum concentrations, and very higher tungsten concentration compared to the matrix phases. It also showed higher molybdenum and tungsten concentrations than the ${\sigma}$ phase. The decomposition of the ferrite phase into the ${\gamma}_2$ and ${\sigma}$ phases was retarded by W substitution for Mo. Thus, the number of ${\chi}$ phases increased. The impact value was decreased by the substitution of W for Mo. The impact toughness rapidly decreased with time when the ${\chi}$ phase began to precipitate in the initial stage of aging. The impact toughness was, therefore, greatly influenced for the precipitation of the ${\chi}$ phase.