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Vanadium-Boride코팅의 고온 내입자침식성 평가
이의열 ( E. Y. Lee ),김종하 ( J. H. Kim ),정세일 ( S. I. Jeong ),이선호 ( S. H. Lee ),엄기원 ( G. W. Eum ) 한국부식방식학회(구 한국부식학회) 2015 Corrosion Science and Technology Vol.14 No.2
The components in ultra super critical (USC) steam turbine, which is under development for high efficient power generation, are encountering harsher solid particle erosion by iron oxide scales than ones in the existing steam turbines. Therefore, the currently used boride coating will not be able to hold effective protection from particle erosion in USC system and should be replaced by new particle erosion resistant coatings. One of the best protective coatings developed for USC steam turbine parts was found to be vanadium-boride (V-boride) coating which has a hardness of about 3000 HV, much higher than that of boride, 1600∼2000 HV. In order to evaluate particle erosion resistance of the various coatings such as V-boride, boride and Cr-carbide coatings at high temperature, particle erosion test equipments were designed and manufactured. In addition, erosion particle velocity was simulated using FLUENT software based on semi-implicity method for pressure linked equations revised (SIMPLER). Based on experimental results of this work, the vanadium-boride coating was found to be superior to others and to be a candidate coating to replace the boride coating.
이의열,김종하 국립7개대학공동논문집간행위원회 2002 공업기술연구 Vol.2 No.-
The particle erosion by iron oxides such as Fe_3O_4 makes great damage to steam turbine components for power generation. The iron oxides are known to be formed on and separated away from the surface of boiler tubes under elevated temperature, high pressure, and moisture. Damages by these particles increase costs for maintaining and repairing the steam turbines. A general way to decrease the damages is to directly hard-coat the components exposed to particle erosion. Many coatings like nitriding, HVOF, and boronizing have been tried for surface hardening of the components, but the evaluation and comparison of their performances under the condition, in which the steam turbine operates, have not been carried out. Therefore, the particle erosion tester which can offer the condition was developed for evaluating and comparing the performances of the bare Cr/Mo alloy, nitride, 75Cr3C2+25NiCr(by HVOF) and boride. It was observed that the borde coating on the Cr/Mo alloy showed the lowest damages by particle erosion, relative to other coatings and the bare Cr/Mo alloy.
Steam Turbine Nozzle용 12%Cr강의 Paste Boronizing 처리 및 고온표면특성에 관한 연구
조재현,손근수,윤재홍,김현수,이성훈,변응선,이의열,이선호,김인수 대한금속재료학회 2002 대한금속·재료학회지 Vol.41 No.2
12% Cr steel used for a nozzle in steam turbine was paste-boronized and its surface properties at high temperature were evaluated. Typical tooth structure, which consisted of outer layer of FeB and inner layer of Fe_2B, was observed at the boronized layer of the specimen and its activation energy was 286.7 kJ/mole. Cracks due to the difference of thermal expansion coefficient and brittleness of FeB layer were observed. Voids were also observed at tip area of tooth structure. Weight of the specimen exposed at 740℃ increased rapidly from the initial stage of oxidation. Iron oxide was mixed in chromium oxide at outer layer of the oxidized specimen, but chromium oxide and molybdenum were mixed in iron oxide at inner layer. Boronized specimen has shown excellent erosion resistance up to 20 times higher than that of non-treated specimen.