• Korean Journal of Materials Research
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• v.23 no.12
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• pp.702-707
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• 2013

High-quality ${\beta}$-silicon carbide (SiC) coatings are expected to prevent the oxidation degradation of carbon fibers in carbon fiber/silicon carbide (C/SiC) composites at high temperature. Uniform and dense ${\beta}$-SiC coatings were deposited on carbon fibers by low-pressure chemical vapor deposition (LP-CVD) using silane ($SiH_4$) and acetylene ($C_2H_2$) as source gases which were carried by hydrogen gas. SiC coating layers with nanometer scale microstructures were obtained by optimization of the processing parameters considering deposition mechanisms. The thickness and morphology of ${\beta}$-SiC coatings can be controlled by adjustment of the amount of source gas flow, the mean velocity of the gas flow, and deposition time. XRD and FE-SEM analyses showed that dense and crack-free ${\beta}$-SiC coating layers are crystallized in ${\beta}$-SiC structure with a thickness of around 2 micrometers depending on the processing parameters. The fine and dense microstructures with micrometer level thickness of the SiC coating layers are anticipated to effectively protect carbon fibers against the oxidation at high-temperatures.

• Journal of the Korean institute of surface engineering
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• v.45 no.6
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• pp.232-241
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• 2012

Cr-Ti-B-N coatings were synthesized by a hybrid coating system combining high power impulse magnetron sputtering (HIPIMS) and DC pulse magnetron sputtering from a $TiB_2$ and a Cr target in argon-nitrogen environment, respectively. By changing the power applied on the Cr and $TiB_2$ cathodes, the Cr-Ti-B-N coatings with various Ti/Cr ratio and B content were deposited. The phase structure, microstructure and chemical compositions of the Cr-Ti-B-N coatings were studied by X-ray diffraction (XRD), transmission scanning electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). With increase of Cr element in the coatings, the nanocomposite microstructure consisting of nano-sized (Cr, Ti) N crystallites and amorphous BN phase were obtained in the coatings. The microhardness of the Cr-Ti-B-N coatings exhibited a peak value of ~41 GPa for the $CrTi_{0.1}B_{0.4}N_{1.3}$, and then decreased with further increase of Cr content in the coatings, and all the coatings exhibited low friction coefficient. The oxidation and corrosion behavior of the Cr-Ti-B-N coatings revealed better properties due to the formation of a nanocomposite microstructure.

• Proceedings of the KWS Conference
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• 2006.05a
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• pp.45-47
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• 2006

The rotating components in the hot sections of land-based gas turbine are exposed to severe environments during several tens thousand operation hours at above $1100^{\circ}C$ operation temperature. To protect such components from high temperature oxidation, an intermediate bond coat is applied, typical of a MCrAlY-type metal alloy. This study is concerned with the thermal cyclic behavior of thermal barrier coatings. The MCrAlY bond coatings are deposited by HVOF (High Velocity Oxygen Fuel) method on a nickel-based superalloy (GTD-111). Thermal cyclic tests at $1100^{\circ}C$ in ambient air for various periods of time were used to evaluate the thermal cyclic resistance of the TBC coating. The microstructure and morphology of as-sprayed and of thermal cycled coatings were characterized by scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD).

• Korean Journal of Materials Research
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• v.14 no.2
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• pp.110-114
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• 2004

High velocity oxy-fuel sprayed NiCoCrAlY coatings were oxidized between 1000 and $1200^{\circ}C$ in air, and the oxide scales were examined by XRD, SEM/EDS, and EPMA. The unoxidized coatings consisted mainly of ${\gamma}$'$-Ni_3$Al, with some ${\gamma}$-Ni. The major oxide formed on the coatings was $\alpha$ $-Al_2$$O_3$. Additionally, (CoCr$_2$$O_4$, $CoAl_2$$O_4$) spinels and $Al_{5}$ $Y_3$$O_{12}$ coexisted. NiO was not found, despite of high amount of Ni in the coating. Below the oxide layer, internally formed $Al_2$$O_3$ existed.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.692-693
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• 2006

Behavior of stoichiometric and near-stoichiometric NiAl at plasma spray deposition, without and with a bond coat, for coating layers realization on a low alloyed steel substrate, has been investigated. In all variants, NiAl particle melting and subsequent welding at the impact with substrate were observed, forming a relatively compact and adherent coating layer with the NiAl stability maintaining - all assuring the coating layer oxidation and corrosion resistance. Good results from these points of view, also validated through corrosion tests, were obtained for 45:55 Ni:Al composition without a bond coat but adopting an Ar protective surrounding of plasma jet.

• Journal of the Korean institute of surface engineering
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• v.36 no.6
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• pp.430-436
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• 2003

The nanoocrystalline Ni-l5W(at.%) coating electrodeposited on the high carbon steel was oxidized at 700 and $800^{\circ}C$ in air, and the resultant oxidation properties were investigated using XRD, EPMA, TGA and TEM. The oxidation resistance of the coating was not so good that most of the coating was oxidized after oxidation at $800^{\circ}C$ for 5 hrs. The oxidation led to the formation of the outer, thin NiO oxide scale and the inner, porous, rather thick ($NiWO_4$＋NiO) mixed layer containing a bit of $WO_2$. During oxidation, substrate elements such as Fe and Cr diffused outwardly toward the coating, according to the concentration gradient.

• Journal of the Korean Ceramic Society
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• v.32 no.11
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• pp.1315-1321
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• 1995

The optimal coating condition for chrominum carbide coating was selected by Taguchi method. The wear tests with coated specimens by HVOF method were performed in the temperature to 80$0^{\circ}C$. Applied normal loads were selected to be from 8N to 30N. The worn surfaces and subsurfaces were characterized by XRD, EPMA, AES and SEM. The wear track increased with increasing applied normal load, and in terms of the temperature range from 400 to $600^{\circ}C$, below that range, the wear track increased, and above that temperature ragne, the wear track decreased. The degree of oxidation caused by the test temperature and the frictional heating was responsible to the unique high temperature wear behavior chromium carbide coatings.

• Journal of the Korean Ceramic Society
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• v.45 no.10
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• pp.600-604
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• 2008

Although titanium-ceramic systems have gained substantial interests in dental prosthetic field, bonding problem between porcelain and titanium has not been solved. Main obstacle in titanium-porcelain bonding is excessive oxidation of titanium during porcelain firing. The effects of several coating materials on the bonding strength of titanium-porcelain system were investigated in this study. RF sputtering and electroplating of platinum significantly increased the bonding strength of porcelain-titanium specimen. However, coatings of Ni-Au, Ir, and ceramics(zirconia and hydroxyapatite) did not showed a significant effect on bonding strength. Platinum might be a promising material for the protective layer of excessive oxidation of titanium during porcelain firing, resulting in increase in the bonding strength.

• Journal of the Korean Vacuum Society
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• v.6 no.S1
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• pp.166-171
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• 1997

IBED is a very promosing thin film deposition method because of its many advantages, such as excellent adhesion property of films to substrates, room temperature processing, ease of control over the composition and thickness of films, and so on, over the conventional techniques, It has been widely applied in the field of surface modification of materials in the last decade. In our laboratory, many kinds of thin films, such as wear-resistant hard coatings, corrosion and oxidation protective coatings, biomaterial films, buffer layer for high temperature superconductor films, and oxygen sensitive film, have been synthesized by IBED, and several industrial applications of the IBED films have been conducted.

• Journal of the Korean institute of surface engineering
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• v.44 no.3
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• pp.89-94
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• 2011

In this study, the photocurrent characteristics of plasma sprayed $TiO_2$ coatings have been investigated according to additive transition metal (Fe, Mn, Nb powder) and heat treatment conditions. The plasma sprayed $TiO_2$ coatings by heat treatment at $400^{\circ}C$ and 90 min had the higher photocurrent at ultraviolet light, no photocurrent at visible light. The photocurrent of plasma sprayed $TiO_2$ coatings added by Fe, Mn, Nb (named by plasma sprayed $TiO_2$ composite coatings) was lower than that of plasma sprayed $TiO_2$ coatings at ultraviolet light, as was low in intensity ratio of XRD(101)/(110). and the atomic percentage of oxygen by plasma sprayed $TiO_2$ composite coatings was higher than that by plasma sprayed $TiO_2$ coatings. The photocurrent of plasma sprayed $TiO_2$ composite coatings in heat treatment at $400^{\circ}C$ and 90 min was higher than that of plasma sprayed $TiO_2$ coatings in same heat treatment conditions at ultraviolet and visible light, as was high in oxygen affinity by heat treatment.