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초고속 스핀들의 내구성 향상을 위한 WC-Co 분말의 HVOF 용사 코팅
김길수(K.S. Kim),백남기(N.K. Baek),윤재홍(J.H. Yoon),조동율(T.Y. Cho),윤석조(S.J. Youn),오상균(S.K. Oh),황순영(S.Y. Hwang),천희곤(H.G. Chun) 한국표면공학회 2006 한국표면공학회지 Vol.39 No.4
High velocity oxygen fuel(HVOF) thermal spray coating of WC-Co powder is one of the most promising candidate for the replacement of the traditional hard chrome plating and ceramics coating because of the environmental problem of the very toxic Cr6+ known as carcinogen and the brittleness of ceramics coating. WC-Co micron and nano powder were coated by HVOF thermal spraying method for the study of durability improvement of the high speed spindle. Coatings were planned by Taguchi program for the four spray parameters of spray distance, flow rates of hydrogen, oxygen and powder feed rate. Optimal coating process was obtained by the studies of coating properties such as porosity, surface roughness, micro hardness, and microstructure. WC-Co micron and nano powder were coated on the Inconel 718 substrate by the optimal coating process obtained in this study. The wear behaviors were studied by the sliding wear tester at room temperature and at an elevated temperature of 500°C for the application to high speed spindle. Sliding wear test was carried out for four most promising hard coatings of chrome coating, ceramics coatings such as Al₂O₃, Cr₂O₃ and HVOF Co-alloy T800 for the comparison of their wear behaviors. HVOF WC-Co coating was better than other coatings showing highest micro hardness of 1400 Hv and comparable friction coefficients with others. HVOF WC-Co coating is a strong candidate for the replacement of the traditional hard chrome plating for the high speed spindle.
초고속 화염용사 공정변수에 따른 나노 WC-Co의 코팅특성 평가
김병문,황순영,최한신,이창희 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.10
High velocity oxy-fuel thermally sprayed coating of the WC-Co cermet material is a well-established process for modifying the surface properties of the structural components exposed to the corrosive and wear attacks. The hard WC phase in the coating resists to the wear while the soft metallic Co increases the adhesive and cohesive bonding properties. The coating properties deposited by the HVOF process are greatly dependent on the feedstock materials and processing parameters. The effects of the feedstock material and process parameters including the inflight particle parameters and resultant coating microstructures were observed in this study. Both the NW10Co powder containing nano-sized WC particle and the micro-sized WC embedded MW12Co powder were thermally sprayed by the table of orthogonal array of the processing parameters. The in-flight particle parameters such as the particle temperature and velocity were directly measured along the hot gas downstream using the DPV-2000 system. In-flight particle parameters were affected by the properties of the feedstock materials. Especially, the particle temperature of the NW10Co was higher than that of the MW12Co from the barrel exit point to the deposition point, irrespective of the condition of the processing parameters. Porosity in the as-sprayed HVOF coating was measured using an image analyzer. And the Vickers microhardness was measured under applied load of 300 g for 15 seconds. Phase compositions of the as-sprayed HVOF WC-Co coatings were measured and analyzed using the X-ray diffraction. The effects of the feedstock materials and process parameters on the coating properties of the as-sprayed HVOF coatings were discussed in terms of the in-flight particle properties during processing.
조재억,황순영,김규영 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.12
A study was made to investigate the corrosion and corrosion-wear performances in strong acid (5 wt% H₂SO_(4)) solution for the high-velocity oxygen-fuel (HVOF) sprayed coatings of tungsten carbide (WC) cermets. Four different alloy compositions were used as WC cermet coating materials in this study, and they were WC-Co, WCNi, WC-Co-Cr and WC-CrC-Ni. The immersion test and electrochemical test showed that galvanic corrosion occurred between WC particle and binder metal in the coating layer and general corrosion occurred on metallic binder for non-Cr added WC-Co and WC-Ni coatings. The best anti-corrosion properties were observed in the metallic Cr containing WC-Co-Cr layer, which was presumably due to the formation of beneficial chromium oxide on the coating surface. It was found that the corrosion resistance of WC cermet coatings was dependent on the compositions of binder metals as well as the micro-crack ratio of coated layer. (Received June 12, 2004)
알루미늄 확산코팅된 내열 스테인리스강의 반복주기 고온부식 거동
송진엽,황순영,성병근,김규영 대한금속재료학회(대한금속학회) 1992 대한금속·재료학회지 Vol.30 No.7
To improve the corrosion resistance of heat resistant stainless steels (HRSS) at high temperature, pack aluminization of these steels was performed. Two kinds of HRSS (MO-RE 1, HK40) were used for pack aluminization during which the activity of an aluminum source was varied. Various microstructures of the aluminized HRSS were studied. To evaluate and study the corrosion resistance, cyclic corrosion tests in simulated COG (coke oven gas) combustion environment were performed. After the tests, the degradation mechanisms of the pack aluminized HRSS were presented. Especially, the inward diffusion rate of aluminum in aluminized HRSS was more pronounced than that in aluminized Ni-base alloys. In addition, the pack aluminized HRSS in the medium low activity of the aluminum source showed much better corrosion resistance than the uncoated HRSS.