• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.23-28
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• 2019

The structural integrity of a surface metal coating was evaluated through numerical results to improve the efficiency and reduce the damage caused by cavitation in ships and marine plants. The goal was to ensure structural strength and performance, even if the thickness of the wing is reduced to reduce the weight of the material and surface coating. Analytical methods were used for four models: a non-coating model, one with the same thickness after coating, one with a thickness reduction of 3% after coating, and one with thickness reduction of 5% after coating. With a thickness reduction of 5% after coating, the stress was increased to 12%, and the safety factor was 0.99%, so the structural integrity was insufficient. However, a better material or a thicker coating could allow a sufficient safety factor to be secured. The structural integrity was improved by the coating, and even when the weight was reduced up to 5%, the structural integrity could be sufficiently secured due to the coating effect.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.3 s.192
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• pp.91-99
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• 2007

Fractures of galvannealed coating layer during actual press forming in automotive applications were observed by scanning electron microscopy in order to understand fracture mechanism. Fracture behaviors of galvannealed coating layer in extra deep drawing quality steels and high strength steels have been studied by performing the tests describing the representative plastic deformation in sheet metal forming such as uni-axial tensile test, compression test, bi-axial test and plane strain test. Growth and direction of cracks were deeply related to the plastic deformation modes and history. The material properties of galvannealed coating layer were investigated by nano-indentation test equipped with Berkovich diamond indentor for the specimens. Hardness and elastic modulus of the coating layer were higher than bared steels and that was the reason for crack of coating layer. Flat friction test and drawbead friction test were performed to observe the effect of the surface morphology on the frictional characteristics. The micro-plasto hydrodynamic lubrication were appeared and played an important role in reducing the coefficient of friction.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.4
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• pp.99-106
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• 2006

High velocity oxygen-fuel thermal spray coating of the WC-Co cermet material is a well-established process for modifying the surface properties of the structural components exposed to the corrosive and wear attacks, and also these coating are well-known method to improve the fatigue strength of material. In this study, HVOF coated SM490B are prepared to evaluation of the effect of coating on tension and fatigue crack growth behavior. The pre-crack of the fatigue crack growth test specimens machined at deposited material area, heat affected zone and boundary, respectively. Through these test, the following results are obtained: 1) Tensile strength was about 498 MPa, and fracture occurred on base metal area. 2) The fatigue crack of coated specimens propagated more rapidly than non-coated specimen in all specimens. 3) In the same coating thickness specimens, the specimens with pre-crack at boundary more rapidly propagated than the specimens with pre-crack at HAZ and deposited material area. These results can be used as basic data in a structural integrity evaluation of rolled SM490B weldments considering HVOF coating.

• Journal of Surface Science and Engineering
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• v.20 no.2
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• pp.49-59
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• 1987

The properties of $Cr_2O_3-Al_2O_3-SiO_2$ composite oxide coatings on steel surface were investigated. The results obtained were as follows: The microhardness of oxide coating layer increased with increasing heat-treatment temperature and $Cr_2O_3$ content in coating layer. The hardness showed the highest value (850Hv) treated at 700$^{\circ}C$ for $SiO_2:Al_2O_3:Cr_2O_3$=1:1:4. Increasing heat-treatment temperature, corrosion current density became lower and coating layer became denser. The corrosion current density showed the lowest value $(6.5{\times}10^{-5}\;Acm^2)$ treated at 750$^{\circ}C\;for\;SiO_2:Al_2O_3:Cr_2O_3$=1:1:3. These results were explained by protective layer which was formed during heat-treatment. The bonding between matrix and coating layer is expected to be made mechanically and chemically by the inter diffusion of Ni and Fe. The composite oxide coating was formed by softening of the binder with increasing heat-treatment temperature. The strengthening of coating layer is to be resulted from the dispersion of major oxide particles.

• Korean Journal of Metals and Materials
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• v.46 no.3
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• pp.182-188
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• 2008

Carbon nanotubes(CNTs) have outstanding mechanical, thermal, and electrical properties. Thus, by placing nanotubes into appropriate matrix, it is postulated that the resulting composites will have enhanced properties. Cold spray can produce thick metal-based composite coatings with very high density, low oxygen content, and phase purity, which leads to excellent physical properties. In this study, we applied cold spray coating process for the consolidation of Cu/CNT composite powder. The precursor powder mixture, in which CNTs were filled into copper particles, was prepared to improve the distribution of the CNT in copper matrix. Pure copper coating was also conducted by cold spraying as a reference. Annealing heat treatment was applied to the coating to examine its effect on the properties of the composite coating. The hardness of Cu/CNT composite coating represented similar value to that of pure copper coating. It was importantly found that the electrical conductivity of the Cu/CNT composite coating significantly increased from 53% for the standard condition to almost 55% in the optimized condition, taking annealed ($500^{\circ}C/1hr$.) copper coating as a reference (100%). The thermal conductivity of Cu/CNT composite coating layer was higher than that of pure Cu coating. It was also found that the electrical and thermal conductivities of Cu/CNT composite could be improved through annealing heat treatment. The microstructural evolution of Cu/CNT coating was also investigated and related to the macroscopic properties.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.105-106
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• 2017

The metal spray method, one of the surface anti-corrosion methods to prevent the corrosion of the steel material, does little effects on the material, while it can be used on a wider surface. However, metal spraying is used only in a limited environment, and research on the case of using with concrete is lacking. The purpose of this study was to observe the corrosion behavior of steels with metal spray coatings in concrete using electrochemical methods And to evaluate the performance of the method according to the type of metal used in the metal spray. As a result, the Al metal spray coating showed the best performance, because Aluminum is oxidized in the cement mortar and forms alumina oxide film.

• Journal of the Korean Electrochemical Society
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• v.11 no.2
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• pp.95-99
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• 2008

This study has made the electrode that is coated zirconium oxide on the titanium by ESD(Electrostatic spray deposition) coating methode. It has investigated the effects of the etching method of a Ti substrate as the preparation, making of zirconium oxide film and electrochemical characteristics of the electrode that is etched on the titanium. The HCl etching develops a fine and homogeneous roughness on the Ti substrate. Fabrication and material properties of the metal oxide electrode, which is known to be so effective to generate ozone and hypochlorous acid (HOCl) as power oxidant, were studied. A proper metal oxide material is focus zirconium oxide through reference. A coating method to enhance the fabrication reproducibility of the zirconium oxide electrode was used ESD coating method by zirconium oxychloride. Zirconium oxide films on the Ti substrate were tested using SEM, XRD, Cyclic voltammetry.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.6
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• pp.629-636
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• 2014

For surface modification, bulk metallic glass coatings were fabricated using metallic glass powder and a mixture of a self-fluxing alloy or/and hard metal alloys with a heat-resisting property using a high velocity oxy-fuel coating thermal spraying process. Microstructural analyses and mechanical tests were carried out using X-ray diffraction, a scanning electron microscope, an atomic force microscope, a three-dimensional optical profiler, and nanoindenation. As a result, the monolithic metallic glass coating was found to consist of solid particle and lamellae regions that included many pores. Second phase-reinforced composite coatings with a self-fluxing alloy or/and hard metal alloy additives were employed with in-situ $Cr_2Ni_3$ precipitate or/and ex-situ WC particles in an amorphous matrix. The mechanical behaviors of the solid particles and lamella regions showed large hardness and elastic modulus differences. The mechanical properties of the particle regions in the metallic glass composite coatings were superior to those of the lamellae regions in the monolithic metallic glass coatings, but indicated similar trends in matrix region of all the coating layers.

• The korean journal of orthodontics
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• v.51 no.4
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• pp.270-281
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• 2021

Objective: The aim of this in vitro study was to evaluate the changes in friction between orthodontic brackets and archwires coated with aluminum oxide (Al₂O₃), titanium nitride (TiN), or chromium nitride (CrN). In addition, the resistance of the coatings to intraoral conditions was evaluated. Methods: Stainless steel canine brackets, 0.016-inch round nickel-titanium archwires, and 0.019 × 0.025-inch stainless steel archwires were coated with Al₂O₃, TiN, and CrN using radio frequency magnetron sputtering. The coated materials were examined using scanning electron microscopy, an X-ray diffractometer, atomic force microscopy, and surface profilometry. In addition, the samples were subjected to thermal cycling and in vitro brushing tests, and the effects of the simulated intraoral conditions on the coating structure were evaluated. Results: Coating of the metal bracket as well as nickel-titanium archwire with Al₂O₃ reduced the coefficients of friction (CoFs) for the bracket-archwire combination (p < 0.01). When the bracket and stainless steel archwire were coated with Al₂O₃ and TiN, the CoFs were significantly lower (0.207 and 0.372, respectively) than that recorded when this bracket-archwire combination was left uncoated (0.552; p < 0.01). The friction, thermal, and brushing tests did not deteriorate the overall quality of the Al₂O₃ coatings; however, some small areas of peeling were evident for the TiN coatings, whereas comparatively larger areas of peeling were observed for the CrN coatings. Conclusions: Our findings suggest that the CoFs for metal bracket-archwire combinations used in orthodontic treatment can be decreased by coating with Al₂O₃ and TiN thin films.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.416-416
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• 2016

Organic-inorganic metal halide perovskite solar cells have received attention because it has a number of advantages with excellent light harvesting, high carrier mobility, and facile solution processability and also recorded recently power conversion efficiency (PCEs) of over 20%. The major issue on perovskite solar cells have been reached the limit of small area laboratory scale devices produced using fabrication techniques such as spin coating and physical vapor deposition which are incompatible with low-cost and large area fabrication of perovskite solar cells using printing and coating techniques. To solution these problems, we have investigated the feasibility of achieving fully printable perovskite solar cells by the blade-coating technique. The blade-coating fabrication has been widely used to fabricate organic solar cells (OSCs) and is proven to be a simple, environment-friendly, and low-cost method for the solution-processed photovoltaic. Moreover, the film morphology control in the blade-coating method is much easier than the spray coating and roll-to-roll printing; high-quality photoactive layers with controllable thickness can be performed by using a precisely polished blade with low surface roughness and coating gap control between blade and coating substrate[1]. In order to fabricate perovskite devices with good efficiency, one of the main factors in printed electronic processing is the fabrication of thin films with controlled morphology, high surface coverage and minimum pinholes for high performance, printed thin film perovskite solar cells. Charge dissociation efficiency, charge transport and diffusion length of charge species are dependent on the crystallinity of the film [2]. We fabricated the printed perovskite solar cells with large area and flexible by the bar-coating. The morphology of printed film could be closely related with the condition of the bar-coating technique such as coating speed, concentration and amount of solution, drying condition, and suitable film thickness was also studied by using the optical analysis with SEM. Electrical performance of printed devices is gives hysteresis and efficiency distribution.