• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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• pp.175-177
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• 2012

A corrosion resistance and hard nitrocarburized layer was distinctly formed on 310 austenitic stainless steel substrate by DC plasma nitrocarburizing. Basically, 310L austenitic stainless steel has high chromium and nickel content which is applicable for high temperature applications. In this experiment, plasma nitrocarburizing was performed in a D.C. pulsed plasma ion nitriding system at different temperatures in $H_2-N_2-CH_4$ gas mixtures. After the experiment structural phases, micro-hardness and corrosion resistance were investigated by the optical microscopy, X-ray diffraction, scanning electron microscopy, micro-hardness testing and Potentiodynamic polarization tests. The hardness of the samples was measured by using a Vickers micro hardness tester with the load of 100 g. XRD indicated a single expanded austenite phase was formed at all treatment temperatures. Such a nitrogen and carbon supersaturated layer is precipitation free and possesses a high hardness and good corrosion resistance.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.04a
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• pp.169-171
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• 2007

에어컨 콤프레셔 실린더에 도금되는 3가 크롬의 도금 두께 균일화를 위하여 컴퓨터 시뮬레이션 작업을 수행하였다. 컴퓨터 시뮬레이션의 정확도를 위하여 현장에서 사용되는 경질 3가 크롬의 전기화학적 특성을 측정하였다. 그리고, 이를 입력 값으로 하여 헐셀에 대하여 실험과 컴퓨터시뮬레이션을 수행하였다. 이 시뮬레이션 결과를 실제의 헐셀 실험 결과와 비교 검토함으로써 컴퓨터 시뮬레이션의 타당성정도를 점검하였고, 3가 크롬의 특성을 비교분석하였다. 이러한 자료를 근거로 3가 크롬 도금두께 균일화를 위한 시뮬레이션 작업을 에어컨 콤프레셔 실린더에 적용시켜 최적의 도금조건을 도출하였다.

• 연구논문집
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• s.26
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• pp.121-132
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• 1996

The carburising surface modification treatment of the die steel has been used for improving wear resistance and heat cycle strength of the die and preventing a pitting on the surface because the carbides are forming in the matrix during carburising. Generally, the hot forging die was used after quenching-tempering treatment or nitriding after quenching-tempering treatment. The nitriding after carburising on the surface of a hot die steel and a wear resistance die steels was suggested by SOUCHARD, JACQUOT. and BUVRON. This surface modification treatment improved the adhesive and abrasive wear resistance and friction coefficient. The process was introduced to the forging die of stainless steel, titanium alloy steel, alloy and medium carbon steel and the physical properties of the die after the treatment were improved. The surface hardening treatment of the nitriding, the carburising, the boriding, and TD process were used to improved the life time of the forging die. Also, the coating process of PVD, CVD and PCVD were used and the hard chromium plating was occasionally used. Therefore, this study analyzed the effects of the carburising time and the conditions of nitriding on STD61 steel. The case depth, the surface hardness, the forming carbide size and shape during overcarburising process on the die steel were also examined.

• Journal of the Korean institute of surface engineering
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• v.19 no.2
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• pp.31-43
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• 1986

The properties of the electroless nickel deposit mainly depends on the pH of the bath, the plating temperature, and the molar ratio of nickel to hypophosphite but they are also affected by its formulation and concentration of complexing and buffering agents. According to changeing the concentration of triethanolamine and boric acid, phosphorous contents, microsturcture, crystalline, hardness and wear resistance of deposits obtained from ammoniacal alkaline bath were investigated by EPMA, differential thermal analyser, X-ray diffractometer and wear tester. The results are as follows; (1) Increasing concentration of triethanolamine in the bath, the deposits is slightly inclined to increase its phosphorous content(3.7% P). (2) In the as-plated state, the deposits are not crystallized state but they are thermally unstable phase, and they are crystallized with precipitating $Ni_3P$ at 400$^{\circ}C$. (3) The deposit containing 2.3% P has higher hardness value in the as plated and heat treated state at below 300$^{\circ}C$ than those of 3.7% phosphorous deposit (1090Hk). But in the case of heat treating at 400$^{\circ}C$, the former has lower hardness value (1000Hk) than the latter and has remarkably Ni(III) orientation by heat treatment. (4) The 3.7% phosphorous deposit heat treated at 400$^{\circ}C$ has better wear resistance than hard chromium plating.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.169-169
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• 2016

크롬산 용액에 황산을 촉매로 하여 Sargent에 의해 개발된 크롬도금은 경도, 내식성, 내마모성 등의 특성이 우수하다. 이로 인해 장식용 박막 도금뿐만 아니라 경질의 후막 도금층을 형성이 가능함으로써 기계 부품류를 비롯한 산업 전반에 걸쳐 폭넓게 적용되고 있다. 이러한 크롬도금이 적용된 소재부품에 대해 장수명화와 더불어 가혹한 환경에서의 사용요구가 점차 증가하고 있으며, 이를 위해서는 보다 더 우수한 내식성과 기계적 물성을 확보해야할 필요성이 높다. 한편 경질 크롬 도금의 내식성과 관련해 도금 과정에서 발생하는 마이크로 크랙에 의해 제품의 내식성의 한계를 나타내게 된다. 본 연구에서는 내식성이 우수할 뿐만 아니라 표면 경도가 우수한 도금층을 얻기 위해 도금 전류 조건으로 펄스 전류를 적용하는 방안을 시도한 것으로 펄스전류를 적용하여 경질크롬도금 시 크랙 발생에 미치는 영향을 조사하였다. 도금욕은 일반적인 경질크롬도금에 사용되는 Sargent 욕을 이용하였고, duty ratio를 조절하여 전류 조건 변화에 따른 단면 내 크랙의 수 변화를 관찰하여 최적의 전류 조건을 도출하였다. 그리고 도출된 전류 조건을 이용해 도금 두께에 따른 크랙 수 변화를 관찰하였고, 이때의 경도를 측정하였다. 또한 XRD 분석을 통해 도금 전류 조건 및 시간 변화에 따른 결정구조 변화를 확인하였다. 실험결과 펄스 전류를 적용하는 경우, 기존 직류 적용 시에 비해 크랙 발생을 현저하게 감소시킬 수 있었으며, 사실상 크랙프리(Crack free) 도금이 가능하였다. 또한 크랙의 감소와 함께 경도 저하가 나타나게 되나 펄스 전류 인자의 최적화에 따라 이러한 경도 저하 현상의 최소화가 가능하였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2001.11a
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• pp.56-56
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• 2001

Ni-W alloy deposit is one of the best alternatives to hard chromium plating because of its good mechanical properties (high hardness, high strength, and good wear resistance). Ni-W alloy is deposited from weakly acidic or alkaline electrolytic bath with nickel sulfate, sodium tungstate or APT, and some kinds of organic hydroxy-acid complex and ammonia salts. W content of the deposit can be changed from 0 to 5Owt% and the coating with high W content is more attracted. But, meanwhile, the deposited layers are always found high internal stress, which cause them to become brittle and to bond insufficiently with the substrate. On the second hand, as the W content is incresed, the current efficiency reduced, which results in large quantities of hydrogen evolution and then produces bubbles on surface and pitting appearance In this paper, the influence of some additives on Ni-W alloy electroplating was investigated by means of compositional analysis and SEM. The initial results showed that 2-butyne-1,4-diol was the best brightener for Ni-W plating process. It could brighten and level deposit, but decreased the cathodic current efficiency. Its optimum concentration range is from O.lgjL to 0.5gjL. Besides, three kinds of additives including 2-butyne-1,4-diol were examined with Dagguchi method.

• Journal of the Korean institute of surface engineering
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• v.19 no.3
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• pp.83-91
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• 1986

Codeposited of boron nitride(BN) particle dispersed into electroless nickel-phosphours (Ni-P) and nickel-boron(Ni-B) platings were studied for the purpose of developing the wear resistance and lubricity. BN can be codeposited from electroless nickel plating bath with $NaH_2PO_2$ and $NaBH_4$ as the reducing agents. Most dispersolids were distributed uniformly in the Ni-P and Ni-B matrix. Abrasion loss decreased with increasing amount of codeposits and reached a constant value 2.4 percent by volume percent of BN particle. The wear resistance and the friction coefficient of the heat treated BN composite coatings were improved about three times than that of as-coatings. The BN composite coatings were more wear resistance than hard chromium. Ni-B-BN composite coatings showed lower wear resistance and friction coefficient than Ni-P-BN. The BN content of the deposite was found to be 2.4 v/o for these optium conditions.

• Journal of the Korean institute of surface engineering
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• v.54 no.3
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• pp.139-143
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• 2021

Cr-Al-N coatings were deposited onto WC-Co substrates using a cathodic arc evaporation (CAE) system. CAE technique is recognized to be a very useful process for hard coatings because it has many advantages such as high packing density and good adhesion to metallic substrates. In this study, the influence of deposition temperature as a key process parameter on film growth behavior and mechanical properties of Cr-Al-N coatings were systematically investigated and correlated with microstructural changes. From various analyses, the Cr-Al-N coatings prepared at deposition temperature of 450℃ in the CAE process showed excellent mechanical properties with higher deposition rate. The Cr-Al-N coatings with deposition temperature around 450℃ exhibited the highest hardness of about 35 GPa and elastic modulus of 442 GPa. The resistance to elastic strain to failure (H/E ratio) and the index of plastic deformation (H³/E² ratio) were also good values of 0.079 and 0.221 GPa, respectively, at the deposition temperature of 450℃. Based on the XRD, SEM and TEM analyses, the Cr-Al-N coatings exhibited a dense columnar structure with f.c.c. (Cr,Al)N multi-oriented phases in which crystallites showed irregular shapes (50~100nm in size) with many edge dislocations and lattice mismatches.

• The Journal of Advanced Prosthodontics
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• v.4 no.2
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• pp.89-92
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• 2012

PURPOSE. Adequate passive-fitting of one-piece cast 3-element implant-supported frameworks is hard to achieve. This short communication aims to present an alternative method for section of one-piece cast frameworks and for casting implant-supported frameworks. MATERIALS AND METHODS. Three-unit implant-supported nickel-chromium (Ni-Cr) frameworks were tested for vertical misfit (n = 6). The frameworks were cast as one-piece (Group A) and later transversally sectioned through a diagonal axis (Group B) and compared to frameworks that were cast diagonally separated (Group C). All separated frameworks were laser welded. Only one side of the frameworks was screwed. RESULTS. The results on the tightened side were significantly lower in Group C ($6.43{\pm}3.24{\mu}m$) when compared to Groups A ($16.50{\pm}7.55{\mu}m$) and B ($16.27{\pm}1.71{\mu}m$) ($P$ <.05). On the opposite side, the diagonal section of the one-piece castings for laser welding showed significant improvement in the levels of misfit of the frameworks (Group A, $58.66{\pm}14.30{\mu}m$; Group B, $39.48{\pm}12.03{\mu}m$; Group C, $23.13{\pm}8.24{\mu}m$) ($P$ <.05). CONCLUSION. Casting diagonally sectioned frameworks lowers the misfit levels. Lower misfit levels for the frameworks can be achieved by diagonally sectioning one-piece frameworks.

• Journal of Applied Biological Chemistry
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• v.59 no.1
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• pp.83-90
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• 2016

The aim of the present study was to evaluate the degree of metal contamination of the Turag River water and its suitability for irrigation. Twenty water samples were analyzed for physicochemical parameters and metals viz., calcium, magnesium, potassium (K), sodium, copper (Cu), zinc (Zn), iron (Fe), manganese (Mn), lead (Pb), cadmium (Cd), chromium (Cr), and nickel (Ni). All water samples were slightly alkaline to alkaline. Regarding electrical conductivity (EC), all samples were suitable for crop in soils with moderate permeability and leaching. Water samples were medium salinity and low alkalinity hazard classes. In terms of total dissolved solids (TDS), all samples were classified as freshwater. As per sodium adsorption ratio (SAR) and soluble sodium percentage (SSP), all samples were classified as excellent. No residual sodium carbonate (RSC) was detected in any of the samples, indicating suitability for irrigation; and all samples were considered very hard. Cr and Mn contents in all samples were above FAO guideline values and, therefore, these metals were considered toxic. Zn, Cu, Pb, Cd, and Ni concentrations were below acceptable limit for irrigation and do not pose a threat to soil environment. Significant relationships were found between EC and TDS, SAR and SSP, SAR and RSC, and SSP and RSC. The combinations of ions such as K-Zn, K-Fe, K-Cu, K-Mn, K-Pb, Zn-Fe, Zn-Cu, Zn-Mn, Fe-Mn, Cu-Mn, Cu-Pb and Mn-Pb exhibited significant correlation. This study revealed that Turag River water samples are contaminated with Cr and Mn. This fact should not be ignored because water contamination by metals may pose a threat to human health through food chain.