A Study on the Oxidation Behaviors of Power Plant Valve Materials under the Ultra Super Critical Condition
초초 임계 화력 발전소용 밸브 소재의 산화 거동
이준섭;조동율;윤재홍;주윤곤;송기오;조재영;강진호;이선호;엄기원;이종욱;
Lee, J.S.;Cho, T.Y.;Yoon, J.H.;Joo, Y.G.;Song, K.O.;Cho, J.Y.;Kang, J.H.;Lee, S.H.;Uhm, K.W.;Lee, J.W.;
창원대학교 나노신소재공학부;두산 중공업(주);
School of Nano and Advanced Materials Engineering, Changwon National University;Doosan Heavy Industries & Construction Co. Ltd.;
DOI : 10.5695/JKISE.2009.42.1.026
Recently ultra-supercritical steam power plants operate at $1000^{circ}F$ ($538^{circ}C$) and 3500 psi (24.1 MPa). Thermal efficiency of power plant will be increased about 2% if steam temperature increases from $1000^{circ}F$ to $1150^{circ}F$ ($621^{circ}C$). In this study valve materials Incoloy901 (IC901) and Inconel718 (IN718) were nitrided to improve the surface hardness and solid lubrication function of the valve materials. The hardness of both IC901 and IN718 increased about two times by ion nitriding. IC901, IN718 and their nitrided specimens were corroded under ultra super-critical condition (USC) of $621^{circ}C$. and 3600 psi (24.8 MPa) for 2000 hours. Oxidations of both IC901 and IN718 were very small due to the formation of protective oxide layer on the surface. But the corrosion resistance of both nitrided specimens decreased because of the formation of non-protective nitride layer of $Fe_{4}N$, $Fe_{2}N$ and CrN on the surface layer. The hardness of both nitrided IC901 and IN718 at $20{mu}m$ depth from the surface decreased about 30% and 20% respectively by USC 2000 hours.
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