음극아크증착법으로 합성한 다층박막의 국부부식 기구에 관한 연구

김호건(Ho-Gun Kim),안승호(Seung-Ho Ahn),이정호(Jeong-Ho Lee),김정구(Jung-Gu Kim),한전건(Jeon-Gun Han) 한국표면공학회 2003 한국표면공학회지 Vol.36 No.4

탈기된 3.5 wt.% NaCl 용액 환경에서의 스테인리스 강에 증착된 CrN 박막의 Si 첨가에 따른 영향 평가

김우중(Woo-Jung Kim),최윤석(Yoon-Seok Choi),김정구(Jung-Gu Kim),이호영(Ho-Young Lee),한전건(Jeon-Gun Han) 한국표면공학회 2005 한국표면공학회지 Vol.38 No.4

CrSiN coatings of stepwise changing Si concentration were deposited on stainless steel by closed field unbalanced magnetron sputtering (CFUBM) system. Microstructure of the films due to the Si concentration is measured by XRD. The corrosion behavior of CrSiN coatings in deaerated 3.5% NaCl solution was investigated by potentiodynamic test, electrochemical impedance spectroscopy (EIS) and surface analyses. The microstructure of CrSiN film depends on the Si concentration. When Si/(Cr+Si) was under 11.7%, preferred orientation is defined at CrN(220), CrN(311) and Cr₂N(111). The results of potentiodynamic polarization tests showed that the corrosion current density and porosity decreased with increasing Si/(Cr+Si) ratio. EIS measurements showed that the corrosion resistance of Si-bearing CrN was improved by phase transformation of the film, which leads to increase of pore resistance and charge transfer resistance. At the Si/(Cr+Si) ratio of 20, the Si-bearing CrN possesses the best corrosion resistance due to the highest pore resistance and charge transfer resistance.

AISI D2강 위에 다층으로 증착된 WC-Ti_(1-X)Al_(X)N 코팅의 국부부식 거동에 관한 연구

안승호,이정호,김호건,김정구,한전건 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.9

Multilayered WC-Ti_(1-x)Al_(x)N coatings are characterized by periodically repeated structures of lamellae of WC-Ti/WC-Ti_(1-x)Al_(x)N. WC-Ti_(1-x)Al_(x)N coatings of changing Al concentration were deposited on AISI D2 steel by high-ionization sputtered plasma vapor deposition (PVD). The Al concentration could be controlled by using evaporation source for Al and fixing the evaporating rate of other metals. Four kinds of WC-Ti_(1-x)Al_(x)N coatings were prepared: WC-Ti_(0.6)Al_(0.4)N, WC-Ti_(0.53)Al_(0.47)N, WC-Ti_(0.5)Al_(0.5)N and WC-Ti_(0.43)Al_(0.57)N. The corrosion behavior of WC-Ti_(1-x)Al_(x)N coatings was investigated using electrochemical techniques in deaerated 3.5% NaCl electrolyte (galvanic corrosion test, potentiodynamic polarization test, electrochemical impedance spectroscopy and Mott-Schottky method) and surface analyses (GDOES, SEM and EDS). Particular attention was paid to the effect of growth defects on the coating properties related to the corrosion behavior. The results of the coating and substrate galvanic corrosion test showed low galvanic current densities. In the potentiodynamic polarization test and EIS measurement, the corrosion current density of WC-Ti_(0.5)Al_(0.5)N was lower than others and presented higher R_(ct) values than others after 240 h immersion time. This could be attributed to the formation of a Ti oxide, which promotes partial closing of the defects. Capacitance values obtained from EIS as a function of different potentials (C^(-2) vs E) showed that the oxide layer exhibited an n-type semiconductor behavior.

플라즈마 산화 처리된 65/35황동의 산소 분압별 부식특성에 관한 연구

박창규,안승호,김정구,정윤모,한전건 대한금속재료학회 2005 대한금속·재료학회지 Vol.43 No.4

Brasses are the most widely used copper-based alloys because of the good corrosion resistance, formability, high strength and excellent hot-working properties. However, dezincification occurs when one or more components of an alloy are more susceptible to corrosion than the rest and, as a result, are preferentially dissolved. In order to enhance the corrosion resistance, the oxide film was deposited on the 65/35 brass by pulsed dc plasma oxidation with various pressure. The corrosion behavior of plasma oxidized brasses with various oxygen pressure was investigated by electrochemical methods (potentiodynamic polarization test, potentiostatic test, electrochemical impedance spectroscopy) and surface analyses (x-ray diffraction, scanning electron microscopy, auger electron spectroscopy, electron probe micro analyzer). Particular attention was paid to the effects of oxygen pressure and oxide thickness on the coating properties related to the corrosion behavior. From the results of electrochemical test, it was found that the oxidized brass under condition of 1.5 Torr oxygen pressure was effective in improving corrosion resistance. It was attributed to the protective oxidized layer (ZnO). Finally, an optimized oxidation condition for corrosion protection was found to be 1.5 Torr oxygen pressure and 1 pun thickness. (Received September 3, 2004)

Calorizing 과 플라즈마질화의 복합처리에 의한 표면 특성 향상에 관한 연구

김상식,이상율,정재원,한전건 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.9

A duplex surface treatment process of calorizing process followed by plasma nitriding was design to develop a process which improves wear resistance as well as oxidation resistance at high temperature. The surface properties of the duplex treated mild steel and STD61 steel were characterized and compared with those of both steels treated by single surface process of calorizing or plasma nitriding, in terms of microstructure, microhardness, wear resistance at room temperature and 500℃, and the oxdation behaviours at high temperatures. Duplex treated specimens were calorized at 1,050℃ for 5 hours and then were subsequently plasma nitrided at 500℃ for 5 hours. The pack cementization process on mild steel had created FeAl compound layer of approximately 120 ㎛ thickness on the surface. Much improved surface microhardness above 1200Hv, (0.1 ㎏) was measured after subsequent plasma nitriding and the nitriding depth was of the order of 80 ㎛. Although STD61 steel showed an decrease in microhardness in the Al-diffused layer upon calorizing, the subsequent plasma nitriding increased the hardness up to 1280Hv and the nitriding depth of over 80 ㎛ was obtained. The room temperature wear resistance of the duplex treated steels was slightly better than that of the nitrided one, but there was considerable improvement of the high temperature wear resistance at 500℃ in the duplex treated steels when both wear volume and weight change due to oxidation were considered. In addition the duplex treated steels showed an improved oxidation resistance than the plasma nitrided steels.

복합표면처리된 AISI H13 강의 내산화 및 내마모특성

이종훈,박홍진,이상율,정재원,한전건 대한금속재료학회(대한금속학회) 1997 대한금속·재료학회지 Vol.35 No.12

The effects of the duplex treatment on the isothermal oxidation and high temperatures wear resistance of AISI H13 steel were investigated in this work. High temperature wear tests at 500℃ were performed under no lubricant condition in air using a ball-on-disk type tribotester and measurements of oxidation resistance of the duplex treated specimens at 700℃ and 900℃ were obtained by isothermal oxidation test in air. Experimental results showed that oxidation behaviours of duplex treated H13 steel was remarkably dependent upon the type of the intermediate layer between the duplex-treated layer and the substrate. The duplex type A specimen, which has calorized layer as an intermediate layer, did not show any serious oxidation and only partial fracture of the duplex treated layer was observed after 100hours. On the contrary, duplex type B specimen, which has nirided layer as an intermediate layer, showed rapid oxidation of the duplex treated layer even after only 20 hours exposure at 900℃ and the duplex treated layer were completely detached from the base metal after exposure to 900℃ for 50 hours. Among three specimens, only plasma nitrided specimen showed the worst oxidation resistance. From the wear test at 500℃, the wear volume was calculated and the minimum weight loss in duplex type A specimen and the minimum weight loss in the plasma nitrided specimen were measured. The maximum wear depths of wear scars were measured to be approximately 60㎛ for duplex type A, 70㎛ for type B, and 100㎛ for the plasma nitrided specimen.