• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.6
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• pp.895-900
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• 2013

Several plasma spray and metallurgical surface coatings such as $Al_2O_3$, $Cr_2O_3$, WC-Ni, and chromizing coating have been examined for their application in environments with high temperature, wear, and corrosion. The chromizing coating is different from others coatings in the manufacturing process the surface. These coatings' characteristics were tested experimentally, and the results were compared. WC-Ni shows good performance against thermal barrier, wear, and corrosion and is one of the best candidates for the environment considered herein. These coatings were studied for their application in the steel manufacturing industry. The most commonly required functions in this industry are thermal and wear resistance.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.12
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• pp.788-793
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• 2017

Electrical behaviors of plasma-sprayed $Al_2O_3-TiO_2$ coatings have been investigated in terms of their $TiO_2$ content. On increasing the $TiO_2$ content from 6 to 30 wt%, the DC electrical conductivity increased by several orders of magnitude. From impedance spectroscopy analysis, the total conductivity of the grains and grain boundaries and their respective activation energies were determined without the electrode effects that could impede ionic transfer. An electron transference number was also estimated, ranging between 6.5% and 7.3% for 13 wt% $TiO_2$ and between 0.4% and 0.7% for 30 wt% $TiO_2$ in the coating. Because of the high electronic contribution to the total conductivity, the $Al_2O_3-TiO_2$ coating could be a new candidate material to obtain superior electrical conductivity as well as corrosion and wear resistances.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2011.06a
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• pp.229-229
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• 2011

• Korean Journal of Materials Research
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• v.7 no.1
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• pp.76-80
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• 1997

'4 NiAl coating process was applied on 316 stainless steel to retard the corrosion of the wet- seal area of separator for the molten carbonate fuel cell. The Nit11 phasc on the stainless steel substrate could be formed by pre-coating with Ni, plated with A1 and ther, heat treated at $800^{\circ}C$ for 3 hr in $H_2/N_2$ gas atmosphere. The corrosion protection behavior of YiAl coating layer was stuilied under immersion condition in molten cxhonate salt($62^{m}/_{o}Li_2CO_3-38^{m}/_{o}/K_{2}CO_{3}$) at $650^{\circ}C$. The NiAl coating layer ticposited on the AiSi 316 stainless steel had high corrosion resistance in molten carbor. dte salt. The corrosion resistance of XiAl (~~jpoared to be associated with the .A1 oxide formed on the surface of coating layer.

• Corrosion Science and Technology
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• v.3 no.4
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• pp.161-165
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• 2004

Aluminum source in an Al-Fe coating reacts with molten carbonate and develops a protective $LiAlO_2$ layer on the coating surface during operation of molten carbonate fuel cells (MCFC). However, if aluminum content in an Al-Fe coating decreases to a critical level for some reasons during MCFC operation, a stable and continuous $LiAlO_2$ protective layer can no longer be maintained. The aluminum content in an Al-Fe coating can be depleted by two different processes; one is by corrosion reaction at the surface between the aluminum source in the coating and molten carbonate, and the other is inward-diffusion of aluminum atoms within the coating into a substrate. In these two respects, therefore, the decreasing rate of aluminum concentration in an Al-Fe coating was measured, and then the influences of these two aspects on the lifetime of Al-Fe coating were investigated, respectively.

• Journal of the Korean Ceramic Society
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• v.46 no.3
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• pp.288-294
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• 2009

The platelet AlO(OH) nano colloids were prepared by hydrothermal reaction of the $\gamma-Al_2O_3$ obtained with dehydration of $\gamma$-AlO(OH) and dilute $CH_3COOH$ solution. In hydrothermal reaction process, reversible reaction was accompanied between $\gamma-Al_2O_3$ and AlO(OH), and hydrothermal reaction temperature, hydrothermal reaction time and $CH_3COOH$ concentration had an effect on the crystal structure, surface chemical property, surface area, pore characteristics and crystal morphology of the AlO(OH) nano colloid particles. In this study, it was investigated to the hydrothermal reaction condition of the AlO(OH) nano colloid for using catalyst support, heat resisting agent, adsorbents, binder, polishing agent and coating agent. The crystal structure, surface area, pore volume and pore size of the platelet AlO(OH) nano colloids were investigated by XRD, TEM, TG/DTA, FT-IR and $N_2$ BET method in liquid nitrogen temperature.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.12
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• pp.3083-3093
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• 1993

Friction and wear at ceramic coated surfaces of aluminum alloy were experimentally studied using a Ring-on-Block wear test machine. Ceramic materials coated on aluminum alloy surfaces were WC, CrC, $Al_{2}O_{3}$ by a plasma spray; and $Al_{2}O_{3}$,$Al_{2}SiO_{5}$, $Na_{2}B_{4}O_{7}$,$Na_{4}P_{2}O_{7}$, and $Al_{2}O_{3}-ZrO_{2}$ composite coating by an Anodic Spark Depositon. They were tested under the sliding wet contact and compared with aluminum alloys and steels. Test results showed that ceramic coated surfaces, in general, have better anti-wear property than those of aluminum alloys due to increase in the surface hardness ; however, they also showed higher coefficients of friction and changes in wear mechanisms, resulting in brittle fractures.

• Journal of the Korean Ceramic Society
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• v.34 no.7
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• pp.677-684
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• 1997

The effects of fluxes on MgO coating materials for tundish were investigated. As the number of charge in continuous casting was increased, the basicity of tundish slag was decreased due to the increase of silica formed by dissolution from rice hull. As a result, the wear of magnesia lining was increased. In aggregates of MgO coating materials, magnesioferrite was formed by the reaction between magnesia and ferric oxide formed by the oxidation of molten steel, while matrix parts of MgO coating materials were worn by CaO-Al2O3-SiO2 compounds. Silica in rice hull extracted to the molten slag reduced basicity of slag and formed forsterite in the result of its reaction with magnesia lining. Also, fayalite was formed from the reaction between silica and ferric oxide and it caused the increment of magnesia lining's wear. The wear of magnesia lining by flux of CaO-SiO2 was larger than that of Cao-Al2O3 and calcia in the flux increased the wear of magnesia lining through the formation of rankinite.

• Journal of the Korean Ceramic Society
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• v.32 no.8
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• pp.909-914
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• 1995

From alumina powder and TEOS, $\alpha$-Al2O3/SiO2 composite powder for reaction-sintered mullite was synthesized by heterogeneous coagulation and surface coating, and investigated the mullitization reaction and sintering behavor of these powders. In $\alpha$-Al2O3/SiO2 composite powder prepared by heterogeneous coagulation, each alumina particles were surrounded by silica particles of 50~60 nm in size. And the alumina particles in composite powder prepared by surface coating were coated by uniform silica layer with thickness of 50 nm. In both methods, mullitization reaction was completed at 1$650^{\circ}C$ for 3h, and specimen sintered above 145$0^{\circ}C$ was about 95% fo the theoretical relative density. Mullite grains formed from the reaction with composite powders showed spherical shape with a size of 1~2${\mu}{\textrm}{m}$.

• 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.