• Journal of Surface Science and Engineering
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• v.23 no.1
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• pp.16-26
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• 1990

The standrd electrolyte for the electrodeposition of chromium were preparwith reagent grade chromic acid(200g/L), sulfuric acid(pH=1.8)and oxalic acalic acid(640g/L)as additive. Carbon content in chromium plating varied about2.0-3.8 wt% with current density and temperatures of the bath. The hardeness of chromium platings incresed with increasing the annealing temperatures and showed maximum value of about Hv 1700 after annealing at$ 700^{\circ}C$for 60min. But, decreased it as annealing at above $700^{\circ}C$. The reason for varing thee hardness of chromium codeposited with carbon gradually foumed chromium carbide(Cr7C3), but that changed to Cr23C6 as annealing temperature at above $^700{\circ}C$. The X-ray diffraction pattern indicated that chromium carbides, such as Cr7C3 or Cr3C2, formed at formed at above $300^{\circ}C$. titanium coating sputtered on the on surface of chromium plating had performed and determined the hardness after annealing at 500, 600, $700^{\circ}C$ for 60min. the maximum hardeness was about Hv 2400 as annealing at $700^{\circ}C$. The titanium carbide formed in layer was identified by X-ray diffraction. It was confirmed that chromium and titanium carbide has effect of increasing the hardness.

• Korean Journal of Metals and Materials
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• v.49 no.12
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• pp.937-944
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• 2011

Studies have been carried out in order to reduce fuel-cladding chemical interaction (FCCI) behavior of metallic fuel in sodium-cooled fast reactors (SFR) using an electroplating technique. A $20{\mu}m$ thick Cr layer has been plated by the electrochemical method in the Sargent bath over the HT9 (12Cr-1Mo) clad material and diffusion couple tests of the U-10Zr metallic fuel as well as the rare earth alloy (70Ce-29La) have been conducted. The results show that the Cr plating can prevent FCCI behavior along the fuel-clad interface. However, cracks developed through the thickness during plating, which resulted in the migration of some fuel constituents. Variation of bath temperature, application of pulse current, and post heat treatment have been conducted to control such cracks. We found out that some conditions like the pulse current and the post heat treatment enhanced the layer property by reducing the internal cracks and improving the diffusion couple test.

• Journal of Environmental Health Sciences
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• v.29 no.2
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• pp.69-76
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• 2003

Hexavalent chromium may reduce on polyvinyl chloride (PVC) filter during sampling and storage of sample. Recently, new or modified filters for preventing Cr(VI) from the reduction has been introduced. Thus, this study was performed to compare the reduction behaviors of Cr(VI) on several sampling filters and to find the most appropriate filter for airborne Cr(VI) sampling in plating operation. The results were as follows. 1. There were statistically significant differences among PVC, polytetrafluoroethylene (PTFE). glass fiber (GF) and polyvinylidene fluoride (PVDF) filters in recovery rates of spiked Cr(VI) samples by storage time(p<0.05). There was no significant difference between PVC and PTFE filters(p>0.05). The PVC and PTFE filters showed higher recoveries than GF and PVDF filters(p<0.05). 2. The quartz fiber(QF) filter treated with an alkali solution(2% NaOH/3% Na$_2$CO$_3$, 1% NaOH) showed a significantly higher recovery of Cr(VI) by storage time than other filters(GF and QF filter)(p<0.05). There was no difference in recovery of Cr(VI) between alkali-treated and untreated GF it filters(p>0.05). But the QF filters treated with two alkali solution showed a significantly higher recovery than the untreated QF filter(p<0.05). There was no significant difference in recovery of Cr(VI) between QF filters treated with 1% NaOH and 2% NaOH/3% Na$_2$CO$_3$(p>0.05). In conclusion, treatment of QF fillers with alkali solution was most effective in protecting from the reduction of Cr(VI).

• Korean Journal of Materials Research
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• v.13 no.7
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• pp.420-423
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• 2003

Coatings of TiCrN ion-plated on a steel substrate was oxidized at $800^{\circ}C$ in air, and their oxidation mechanism was presented. During oxidation, substrate elements and Ti and Cr in the coating always diffused outwardly to form the oxide scale. Simultaneously, oxygen from the atmosphere diffused inward1y to react with Ti and Cr to form $TiO_2$and $Cr_2$$O_3$, respectively. Also, the counter-diffusion of cations and oxygen resulted in some oxygen dissolution in the unoxidized TiCrN coating, and Fe dissolution in the oxide scale. When the Ti content in the coating was high, the $TiO_2$-forming tendency was strong, while when the Cr content was high, the $Cr_2$$O_3$-forming tendency was strong.

• 연구논문집
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• s.31
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• pp.127-133
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• 2001

In chromium electrodeposition, crack is inevitably accompanied by chromium layer. Behavior of crack formation and crack density were different from the plating conditions such as current density, temperature, waveform of applied current and so on. And cracks have an influence on the corrosion resistance of chromium deposit, because corrosion occurs through the network of cracks between deposit and substrate. Therefore, many researches have been achieved in order to remove the cracks in chromium deposit. Formation of double layers, Cr/Cr and Ni/Cr were investigated to increase corrosion resistance of chromium deposit in this study. As pretreatment prior to outer chromium coating, acid pickling and current control method were examined. Cracks in cross-section of each sample were observed with SEM and CASS(Copper modified acetic acid salt spray) test was performed to evaluate corrosion resistance. It was found that corrosion resistance of Cr/Cr and Ni/Cr double layers were superior to Cr or Ni single layer from the results of CASS test.

• Korean Journal of Materials Research
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• v.15 no.11
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• pp.730-734
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• 2005

Cr-Al-Si-N coatings were deposited on WC-Co substrates by a hybrid coating system of arc ion plating and DC magnet :on sputtering technique in $N_2/Ar$ mixture. The Cr-tll-Si-N coatings were synthesized with different Si contents. Their microstructure and mechanical properties were systematically investigated. The average size of crystallites largely decreases with the increase of Si content compared with Cr-Al-N. The microhardness of Cr-Al-Si-N coatings largely increases from 24 to 55 GPa. The enhanced hardness is believed to originate from the microstructural change by the fine composite microstructure of Cr-Al-N coatings with Si addition. The average friction coefficient of Cr-Al-Si-N coatings decreases from 0.84 to 0.45 with increasing Si content up to $16\;at.\%$.

• Journal of Surface Science and Engineering
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• v.15 no.3
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• pp.127-137
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• 1982

In chemical plating of nickel and chromium on steel, studies on various factors affect-ing the plating operations were carried out. The optimum bath compositions and operat-ing conditions were obtained. The structure and properties of the as deposits or deposits after heat treatment were investigated. (1) The most optimum conditions for the chemical nickel and chromium plating were; 〔Ni2+〕/〔H2PO2-〕; 0.5∼0.8, 〔Cr3+〕/〔H2PO2-〕; 0.6∼0.9 PH;5.0∼5.5, temperature; 90∼95$^{\circ}C$ (2) In the case of nickel deposition, the hardness of deposits increased with increasing phosphorous contents. Heat-treating at the temperature range 200$^{\circ}C$ to 600$^{\circ}C$, the maximum hardness of deposits was obtained at 400$^{\circ}C$ and decreased at temperature above 400$^{\circ}C$ due to growth of Ni3P. (3) Corrosion resistance of chemical nickel deposits was improved with increasing of p-hosphorous contents and heat treating temperature.

• Applied Chemistry for Engineering
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• v.10 no.1
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• pp.67-72
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• 1999

Optimal pretreatment processes for metal plating on engineering plastics, especially on Nylon-inorganic filler alloy was studied. For Nylon-inorganic filler alloy, adhesion strength between resin surface and metal could be improved by just etching process that eliminate amorphous layer. In the SEM picture and surface roughness measurement, etching treatment was found to make enabled the surface condition very rough and the adhesion strength good. It was also found that the surface condition of plated article and its adhesion strength partly depended upon molding condition of Nylon-inorganic filler alloy. EDS, peaks showed that what kinds of and how much of the metal elements remained on the resin surface after pretreatment processes. Cr did not affect on adsorption of Sn and Pd remarkably.

• Journal of Surface Science and Engineering
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• v.39 no.6
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• pp.295-301
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• 2006

Hard chrome plating has been used in surface hard coating over 50 years both for applying hard coating and re-building of worn components. Hard chrome plating solution and mist pollute environment with very toxic $Cr^{6+}$(hex-Cr) known as carcinogen which causes lung cancer, High velocity oxy-fuel (HVOF) thermal spray coatings of WC base cermet and Co-alloy powders are the most promising candidates for the replacement of the traditional hard chrome plating. Surface properties, wear, and friction behaviors of micron size Co-alloy (T800) and micron size WC-l2Co (WC-Co) have been studied for the application as hard coatings. The temperature dependence of wear and friction behaviors of T800 and WC-Co have been investigated at the temperature of $25^{\circ}C$ and $538^{\circ}C$ for the application to high speed spindle.

• Korean Journal of Metals and Materials
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• v.48 no.1
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• pp.90-100
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• 2010

Micro-conductive patterns were microfabricated on an insulating substrate ($SiO_2$) surface by a selective electroless nickel plating process in order to investigate the formation of seed layers. To fabricate micro-conductive patterns, a thin layer of metal (Cu.Cr) was deposited in the desired micropattern using laser-induced forward transfer (LIFT). and above this layer, a second layer was plated by selective electroless plating. The LIFT process. which was carried out in multi-scan mode, was used to fabricate micro-conductive patterns via electroless nickel plating. This method helps to improve the deposition process for forming seed patterns on the insulating substrate surface and the electrical conductivity of the resulting patterns. This study analyzes the effect of seed pattern formation by LIFT and key parameters in electroless nickel plating during micro-conductive pattern fabrication. The effects of the process variables on the cross-sectional shape and surface quality of the deposited patterns are examined using field emission scanning electron microscopy (FE-SEM) and an optical microscope.