초초 임계 화력 발전소용 밸브 소재의 산화 거동
A Study on the Oxidation Behaviors of Power Plant Valve Materials under the Ultra Super Critical Condition
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Recently ultra-supercritical steam power plants operate at 1000oF (538oC) and 3500 psi (24.1 MPa). Thermal efficiency of power plant will be increased about 2% if steam temperature increases from 1000oF to 1150oF (621oC). 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 621oC. 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 Fe4N, Fe2N and CrN on the surface layer. The hardness of both nitrided IC901 and IN718 at 20mm depth from the surface decreased about 30% and 20% respectively by USC 2000 hours.
Abstract
Recently ultra-supercritical steam power plants operate at 1000oF (538oC) and 3500 psi (24.1 MPa). Thermal efficiency of power plant will be increased about 2% if steam temperature increases from 1000oF to 1150oF (621oC). 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 621oC. 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 Fe4N, Fe2N and CrN on the surface layer. The hardness of both nitrided IC901 and IN718 at 20mm depth from the surface decreased about 30% and 20% respectively by USC 2000 hours.
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