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이준섭(J. S. Lee),조동율(T. Y. Cho),윤재홍(J. H. Yoon),주윤곤(Y. G. Joo),송기오(K. O. Song),조재영(J. Y. Cho),강진호(J. H. Kang),이선호(S. H. Lee),엄기원(K. W. Uhm),이종욱(J. W. Lee) 한국표면공학회 2009 한국표면공학회지 Vol.42 No.1
Recently ultra-supercritical steam power plants operate at 1000℉ (538℃) and 3500 psi (24.1 ㎫). Thermal efficiency of power plant will be increased about 2% if steam temperature increases from 1000℉ to 1150℉ (621℃). 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℃. and 3600 psi (24.8 ㎫) 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 20 ㎛ depth from the surface decreased about 30% and 20% respectively by USC 2000 hours.
Plasma Paste Boronizing법에 의한 Ni-Cr-Mo강의 붕화물층 생성거동과 내 토사마모특성에 관한 특성
조재현,박학균,손근수,윤재홍,김현수,김창규,Cho J. H,Park H. K,Son K. S,Yoon J. H,Kim H. S,Kim C. G 한국재료학회 2004 한국재료학회지 Vol.14 No.1
The surface property and formation behavior of a boride layer formed on Ni-Cr-Mo steel in a plasma paste boronizing treatment were investigated. The plasma paste boronizing treatment was carried out at 973~1273 K for 1-7 hrs under the gas ratio of Ar:H$_2$ (2:1). The thickness of the boride layer increased with increasing temperature and time in the boronizing treatment. The cross-section of the boride layer was a tooth structure and the hardness was Hv 2000~2500. XRD analysis revealed that the compound was identified as FeB, $Fe_2$B, and mixed phase of FeB/$Fe_2$B in the boride layer formed at 973~1073 K, 1173K, and 1273K, respectively. The Ni-Cr-Mo alloy boronized at 1173-1273 K showed the best excellent wear resistance against the sand. As a results of corrosion test in 1 M $H_2$$SO_4$ solution, $Fe_2$B formed on the matrix alloy exhibited higher corrosion resistance than FeB.
터보불로워 용 회전체 주축 소재의 마찰,마모 및 부식 저항 향상을 위한 WC- metal 분말의 초고속화염용사코팅
주윤곤 ( Y K Joo ),윤재홍 ( J H Yoon ),조동율 ( T Y Cho ),천희곤 ( H G Chun ) 한국부식방식학회(구 한국부식학회) 2013 Corrosion Science and Technology Vol.12 No.1
High velocity oxy-fuel (1-IVOF) spray coating of WC-metal powder (powder) was carried out to improve the resistances of friction, wear and corrosion of magnetic bearing shall material lnconel7 18 (1n71 8) of turbo blower. A micron sized WC-inetal powder (86.5% WC, 9.5% Co 4% Cr) was coated onto 1n718 surface using HVOF thermal spraying. During the spraying, the binder metals and alloy such as o. Cr and Co-Cr alloy were molten and a small portion of WC particles were partially decomposed to W2C and free carbon at above its decomposition temperature of 1250°C. The free carbon and excessively sprayed oxygen fomied carbon oxide gases. resulting a porous coating of porosity of 2.2±0.3%. The surface hardness of substrate increased approximately three times from 40() H of 1718 to 1260±30 I-h of the coating The friction coefficients of the coating were approximately 0.33 ± 0.03 at 25°C and 0.26 ± 0.03 at 450°C. These values were smaller than those of 1n7 18 substrate at both temperatures due to the lubrication from the free carbon and the cobalt oxide debris. The corrosion resistance of the coating was higher than that of ln718 both in salt water of 3.5% NaCI and acid of I M I-Id solutions, on the contrary, it was lower in base solution of I M NaOH. According to this study. the 1-IVOF WC-metal powder coating is recommended for the durability improvement of magnetic hearing shaft of turbo blower.