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최적 고속화염용사법으로 제조된 Diamalloy4006 코팅의 내마모 특성
주윤곤,윤재홍,정연길,이재현,Joo, Yunkon,Yoon, Jaehong,Jung, Yeongil,Lee, Jehyun 한국재료학회 2015 한국재료학회지 Vol.25 No.9
The effects of coating parameters were investigated in wear resistance coatings of Diamalloy-406 on Inconel 718 to obtain an optimum coating condition by high velocity oxy-fuel spraying. The coating parameters, the flow rates of source gases (hydrogen and oxygen), the powder feed rate, and the spray distance, were designed by the Taguchi method. The optimal conditions were determined: oxygen flow rate 34 FRM, hydrogen flow rate 57 FRM, powder feed rate 35 g/min, and spray distance 7 inch. Friction coefficients of the coating and the substrate decreased with an increasing sliding surface temperature from $25^{\circ}C$ to $450^{\circ}C$. The friction coefficient of Diamalloy-4006 coating decreased as the sliding surface temperature increased from $0.43{\pm}0.01$ at $25^{\circ}C$ to $0.29{\pm}0.01$ at $450^{\circ}C$. The wear trace and wear depth of the coating were smaller than the substrate at all temperatures tested. The relationship between spray parameters and wear resistance was discussed extensively, based on the measured roughness, hardness, and porosity in each coating.
초고속화염용사 WC-CoFe 코팅층의 레이저 표면 열처리 효과
주윤곤,윤재홍,이재현,Joo, Yunkon,Yoon, Jaehong,Lee, Jehyun 한국재료학회 2019 한국재료학회지 Vol.29 No.1
The microstructure, hardness, and wear behaviors of a High Velocity Oxygen Fuel(HVOF) sprayed WC-CoFe coating are comparatively investigated before and after laser heat treatments of the coating surface. During the spraying, the binder metal is melted and a small portion of WC is decomposed to $W_2C$. A porous coating is formed by evolution of carbon oxide gases formed by the reaction of the free carbon and the sprayed oxygen gas. The laser heat treatment eliminates the porosity and provides a more densified microstructure. After laser heat treatment, the porosity in the coating layer decreases from 1.7 % to 1.2 and the coating thickness decreases from $150{\mu}m$ to $100{\mu}m$. The surface hardness increases from 1440 Hv to 1117 Hv. In the wear test, the friction coefficient of coating decreases from 0.45 to 0.32 and the wear resistance is improved by the laser heat treatment. The improvement is likely due to the formation of oxide tribofilms.
최적 고속화염 용사 코팅 공정기술로 제조된 WC-CrC-Ni 코팅의 마모 특성
주윤곤,윤재홍,이재현,Joo, Yunkon,Yoon, Jaehong,Lee, Jehyun 한국재료학회 2017 한국재료학회지 Vol.27 No.2
WC-CrC-Ni coatings were prepared by nine processes of the Taguchi program with three levels for the four spray parameters: spray distance, flow rates of hydrogen and oxygen, and powder feed rate. The optimal coating process (OCP) was oxygen flow rate of 38 FMR, hydrogen flow rate of 53 FMR, powder feed rate of 25 g/min, and spray distance of 7 inches. Hardness of 1150 Hv and porosity of 1.2 %, were obtained by OCP; these are better results compared with the highest 1033 Hv and the lowest 1.5 % porosity obtained by nine processes of the Taguchi program. Friction coefficient of the WC-CrC-Ni coating decreased from $0.36{\pm}0.07$ at $25^{\circ}C$ to $0.23{\pm}0.07$ at $450^{\circ}C$. These values were smaller than those of the EHC (electrolytic hard chrome) plating at both temperatures due to lubrication from the oxide debris. The wear trace and wear depth of the coating are smaller than those of the EHC at both temperatures. Pitting was not found in the WC-CrC-Ni coating sample, while it did appear in the EHC sample.
고속화염용사코팅으로 제조된 WC-CoFe 코팅의 기계적 특성에 관한 연구
주윤곤 ( Yun Kon Joo ),조동율 ( Tong Yul Cho ),하성식 ( Sung Sik Ha ),이찬규 ( Chan Gyu Lee ),천희곤 ( Hui Gon Chun ),허성강 ( Sung Gang Hur ),윤재홍 ( Jae Hong Yoon ) 한국열처리공학회 2012 熱處理工學會誌 Vol.25 No.1
HVOF thermal spray coating of 80%WC-CoFe powder is one of the most promising candidate for the replacement of the traditional hard chrome plating and hard ceramics coating because of the environmental problem of the very toxic Cr6+ known as carcinogen by chrome plating and the brittleness of ceramics coatings. 80%WC-CoFe powder was coated by HVOF thermal spraying for the study of durability improvement of the high speed spindle such as air bearing spindle. The coating procedure was designed by the Taguchi program, including 4 parameters of hydrogen and oxygen flow rates, powder feed rate and spray distance. The surface properties of the 80%WC-CoFe powder coating were investigated roughness, hardness and porosity. The optimal condition for thermal spray has been ensured by the relationship between the spary parameters and the hardness of the coatings. The optimal coating process obtained by Taguchi program is the process of oxygen flow rate 34 FRM, hydrogen flow rate 57 FRM, powder feed rate 35 g/min and spray distance 8 inch. The coating cross-sectional structure was observed scanning electron microscope before chemical etching. Estimation of coating porosity was performed using metallugical image analysis. The Friction and wear behaviors of HVOF WC-CoFe coating prepared by OCP are investigated by reciprocating sliding wear test at 25oC and 450oC. Friction coefficients (FC) of coating decreases as sliding surface temperature increases from 25oC to 450oC. (Received October 31, 2011; Revised November 15, 2011; Accepted December 16, 2011)
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.
SKD61과 Radical Nitriding 처리된 SKD61 기판상에 Arc Ion Plating으로 증착된 TiN 박막의 미세구조 및 기계적 특성, 마찰 및 접착력에 관한 연구
주윤곤(Yun-Kon Joo),윤재홍(Jae-Hong Yoon),방위(Wei Fang),장세굉(Shi-Hong Zhang),조동율(Tong-Yul Cho),하성식(Sung-Sik Ha) 한국표면공학회 2007 한국표면공학회지 Vol.40 No.6
TiN coating on tool steel has been widely used for the improvement of durability of tools. In this work, radical nitriding(RN) is carried out on SKD61 at 450℃ for 5 hours in the ammonia gas pressure 2.7×10³ ㎩. The TiN coating is carried out by arc ion plating(AIP) with the process parameters: arc power 150 A, bias voltage ?50 V, coating time 40 minutes and nitrogen gas pressure 4×10³ ㎩. Hardness, elastic modulus, friction coefficient and adhesion of TiN coating on substrates of both TiN/SKD61 and TiN/RN SKD61 coatings are investigated comparatively. The primary crystalline faces of TiN surface are (200) and (111) for TiN/SKD61 and TiN/RN SKD61 respectively. In addition to the primary phase, Fe phase exists in TiN/SKD61 coating, but not in TIN/RN SKD61. The hardness of TiN/RN SKD61 is about 700 Hv, 250 Hv(56%) higher than that of TiN/SKD61 at the near interface of TiN and substrates. At the TiN surface, hardness of TiN/RN SKD61 is 2,149 Hv, 71 Hv(3%) higher than that of TiN/SKD61. The elastic modulus of TiN coating is improved to 26.7 G㎩(6%) by radical nitriding. The adhesion is improved by the RN coating showing no spalling. buckling and chipping on the scratch test track which are shown on the non-RN TiN/SKD61.
초내열합금 René 80의 응고 조직과 열처리 후 인장특성의 변화
우한별,신종호,주윤곤,이재현,Woo, Hanbyeol,Shin, Jongho,Joo, Yunkon,Lee, Jehyun 한국재료학회 2020 한국재료학회지 Vol.30 No.12
Microstructural characteristics of directionally solidified René 80 superalloy are investigated with optical microscope and scanning electron microscope; solidification velocity is found to change from 25 to 200 μm/s under the condition of constant thermal gradient (G) and constant alloy composition (Co). Based on differential scanning calorimetry (DSC) measurement, γ phase (1,322 ℃), MC carbide (1,278 ℃), γ/γ' eutectic phase (1,202 ℃), and γ' precipitate (1,136 ℃) are formed sequentially during cooling process. The size of the MC carbide and γ/γ' eutectic phases gradually decrease with increasing solidification velocity, whereas the area fractions of MC carbide and γ/γ' eutectic phase are nearly constant as a function of solidification velocity. It is estimated that the area fractions of MC carbide and γ/γ' eutectic phase are determined not by the solidification velocity but by the alloy composition. Microstructural characteristics of René 80 superalloy after solid solution heat-treatment and primary aging heat-treatment are such that the size and the area fraction of γ' precipitate are nearly constant with solidification velocity and the area fraction of γ/γ' eutectic phase decreases from 1.7 % to 0.955 %, which is also constant regardless of the solidification velocity. However, the size of carbide solely decreases with increasing solidification velocity, which influences the tensile properties at room temperature.
Incoloy 909 합금의 최적 알루미나이징 확산 코팅
권순우(S.W. Kwon),윤재홍(J.H. Yoon),주윤곤(Y.K. Joo),조동율(T.Y. Cho),안진성(J.S. Ahn),박봉규(B.K. Park) 한국표면공학회 2007 한국표면공학회지 Vol.40 No.4
An Fe-Ni-Co based superalloy Incoloy 909 (Incoloy 909) has been used for gas turbine engine component material. This alloy is susceptible to high temperature oxidation and corrosion because of the absence of corrosion resistant Cr. For the improvement of durability of the component of Incoloy 909 aluminizing-chromate coating by pack cementation process has been investigated at relatively low temperature of about 550℃ to protect the surface microstructure and properties of lncoloy 909 substrate. As a previous study to aluminizing-chromate coating by pack cementation of Incoloy 909, the optimal aluminizing process has been investigated. The size effects of source AI powder and inert filler Al₂O₃ powder and activator selection have been studied. And the dependence of coating growth rate on aluminizing temperature and time has also been studied. The optimal aluminizing process for the coating growth rate is that the mixing ratio of source Al powder, activator NH₄Cl and filler Al₂O₃ are 80%, 1% and 19% respectively at aluminizing temperature 552℃ and time 20 hours.
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.