• Journal of the Korean institute of surface engineering
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• v.32 no.3
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• pp.253-256
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• 1999

Wet plating has been initiated and developed as a major surface finishing technology as of the long customized and highly productive process until now. As the external compression by virtue of the environmental preservation becomes stricter, there has been new move to adapt dry plating line instead of conventional wet plating one in domestic surface finishing industry. Dry plating, so-called, plasma surface technology has been developed in semiconducting industry and becomes a key technology to be useful as an alternative to wet plating in surface finishing industry. The historical progress of domestic surface finishing industry was outlined with the background on the adaptation of three dry plating processes-plasma spraying, plasma nitriding and ion plating. The present status of domestic industrial activity was covered on major alternative to wet plating.

• Journal of the Korean Ceramic Society
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• v.50 no.5
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• pp.326-332
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• 2013

In this study, we prepared yttria stabilized zirconia granules for thermal barrier coatings using a spray drying process. First, we characterized the properties of granules such as flow rate and packing density for utilizing the air plasma spray process. The flow rate and packing density data showed 0.732 g/sec and 2.14 $g/cm^3$, respectively, when we used larger and denser particles, which are better than hollow granules or smaller spherical granules. Second, we chose larger, spherical granules fabricated in alcohol solvent as starting powders and sprayed it on the bondcoat/nimonic alloy by an atmospheric plasma spray process varying the process parameters, the feeding rate, gun speed and spray distance. Finally, we evaluated representative thermal and mechanical characteristics. The thermal expansion coefficients of the coatings were $11{\sim}12.7{\times}10^{-6}/^{\circ}C$ and the indentation stress measured was 2.5 GPa at 0.15 of indentation strain.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2012.10a
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• pp.131-132
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• 2012

The vacuum plasma coating was performed to analysis the characteristic and find the optimum process conditions for the vacuum plasma spray coating. It was observed that the square shape of powder in case of carbide ceramics does not fluidize well compared to the round shape of powder in case of oxide ceramics so that the plasma spraying is not uniform. The analysis through SEM and EDS mapping shows that the coatings represent excellent structural features with strong resistance against oxidation and satisfied result with vacuum plasma coating.

• Korean Journal of Materials Research
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• v.14 no.3
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• pp.218-223
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• 2004

P-type $\beta$-FeSi$_2$ with a nominal composition of $Fe_{0.92}Mn_{0.08}Si_2$ powders has been produced by mechanical alloying process. As-milled powders were spray dried and consolidated by atmospheric plasma thermal spraying as a rapid sintering process. As-milled powders were of metastable state and fully transformed to $\beta$-$FeSi_2$ phase by subsequent isothermal annealing. However, as-thermal sprayed $Fe_{0.92}Mn_{0.08}Si_2$ consisted of untransformed mixture of $\alpha$-$Fe_2Si_{5}$ and $\varepsilon$-FeSi phases. Isothermal annealing has been carried out to induce transformation to the thermoelectric semiconducting $\beta$-$FeSi_2$ phase. Isothermal annealing at $845^{\circ}C$ in vacuum gradually led to the thermoelectric semiconducting $\beta$-$FeSi_2$ phase transformation, but some residual metallic $\alpha$ and $\varepsilon$ phases were unavoidable even after prolonged annealing. Thermoelectric properties of $\beta$-$FeSi_2$ materials before and after isothermal annealing were evaluated. Seebeck coefficient increased and electric conductivity decreased with increasing annealing time due to the phase transition from metallic phases to semiconducting phases. Thermoelectric properties showed gradual increment, but overall properties appeared to be inferior to those of vacuum hot pressed specimens.

• Journal of Powder Materials
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• v.27 no.4
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• pp.333-338
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• 2020

In this study, we fabricate a thin- and dense-BCuP-5 coating layer, one of the switching device multilayers, through a plasma spray process. In addition, the microstructure and macroscopic properties of the coating layer, such as hardness and bond strength, are investigated. Both the initial powder feedstock and plasma-sprayed BCuP-5 coating layer show the main Cu phase, Cu-Ag-Cu₃P ternary phases, and Ag phase. This means that microstructural degradation does not occur during plasma spraying. The Vickers hardness of the coating layer was measured as 117.0 HV, indicating that the fine distribution of the three phases enables the excellent mechanical properties of the plasma-sprayed BCuP-5 coating layer. The pull-off strength of the plasma-sprayed BCuP-5 coating layer is measured as 16.5 kg/㎠. Based on the above findings, the applicability of plasma spray for the fabrication process of low-cost multi-layered electronic contact materials is discussed and suggested.

• Journal of Power System Engineering
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• v.2 no.3
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• pp.49-54
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• 1998

This paper is investigated of hardness and adhesiveness of plasma sprayed coating steels by AE(Acoustic Emission) testing when loading a tensile. AE Parameters used are Event, Count, Energy and Amplitude. Test specimens are carbon steel(S45C) with sprayed coating layers of Ni-4.5wt.%Al(bond coating) and $TiO_2$(top coating), and carry out heat treatment at $800^{\circ}C\;and\;1000^{\circ}C$, respectively. The micro-hardness of the heat treatment specimen have been improved more than that of non-heat treatment. On the tensile test, the process and occurence of the exfoliation of the sprayed coating layer can be estimated by AE Characteristics of AE parameters, such as event, count, amplitude and energy, on the layer exfoliation are shown the similar aspects. The exfoliation of bond coating occure at about 20% of strain and top coating is about 5% of strain.

• Korean Journal of Materials Research
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• v.24 no.7
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• pp.357-362
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• 2014

Thermal barrier coatings(TBCs) are being applied in many industrial fields such as thermal power generation, aviation and seasonal fields. $ZrO_2-Y_2O_3$(8%) thermal spray coating powders are commercially used as thermal-barrier coating materials to protect against oxidation and corrosion of heat-resistant alloys at elevated temperatures. Currently, $ZrO_2-Y_2O_3$(8%) thermal-spray powder is made using the industrial co-precipitation process, which is very complex and requires a lot of time. In this study, orthorhombic $ZrO_2$ and $Y_2O_3$ powders were fabricated by mechanical mixing, which is more economical than the co-precipitation process. A tetragonal, yttria-stabilized zirconia(YSZ) coating-layer was produced by plasma spraying, using orthorhombic $ZrO_2-Y_2O_3$(8%) powder. Our experimental results indicate that $ZrO_2-Y_2O_3$(8%) mixed powder can be used economically in industry because it is no longer necessary to make this powder by liquid and gas-phase methods.

• Journal of Power System Engineering
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• v.9 no.4
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• pp.90-95
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• 2005

The wire-arc process is a low-cost thermal spray method simply utilizes electrical energy to melt the feedstock wire. It is more userful for field applications, especially to coat large surface area. In this paper, a special Fe-based alloy coatings by using the wire-arc process were developed. Nanoscale composite coatings were achieved either during spraying or through a post heat treatment. As-sprayed Fe-based alloy coatings had been an amorphous matrix structure, after heating to $700^{\circ}C$ for 10 minutes a solid state transformation occurred in the some fraction of amorphous matrix which resulted in the formation of nanostructured recrystallized phase. Scanning electron microscopy (SEM) and field emotional scanning electron microscope(FE-SEM) were applied to analyze the microstructure of the coatings. Additionally hardness and bend resistance of the Fe-based alloy coatings were examined, and these results were compared with those of partially stabilized zirconia(PSZ) coatings by using the plasma spray process.

• Korean Journal of Materials Research
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• v.24 no.2
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• pp.116-122
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• 2014

$Bi_2Sr_2CaCu_2O_x$(Bi-2212) and $Bi_2Sr_2Ca_2Cu_3O_y$(Bi-2223) high-Tc superconductors(HTS) have been manufactured by plasma spraying, partial melt process(PMP) and annealing treatment(AT). A Bi-2212/2223 HTS coating layer was synthesized through the peritectic reaction between a 0212 oxide coating layer and 2001 oxide coating layer by the PMP-AT process. The 2212 HTS layer consists of whiskers grown in the diffusion direction. The Bi-2223 phase and secondary phase in the Bi-2212 layer were observed. The secondary phase was distributed uniformly over the whole layer. As annealing time goes on, the Bi-2212 phase decreases with mis-orientation and irregular shape, but the Bi-2223 phase increases because a new Bi-2223 phase is formed inside the pre-existing Bi-2212 crystals, and because of the nucleation of a Bi-2223 phase at the edge of Bi-2212 crystals by diffusion of Ca and Cu-O bilayers. In this study the spray coated layer showed superconducting transitions with an onset Tc of about both 115 K, and 50 K. There were two steps. Step 1 at 115 K is due to the diamagnetism of the Bi-2223 phase and step 2 at 50 K is due to the diamagnetism of the Bi-2212 phase.

• Journal of the Korea Institute of Building Construction
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• v.21 no.6
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• pp.539-550
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• 2021

In this study, Zn and Zn-15Al were coated on general carbon steel by plasma arc metal spraying and then immersed in a 3.5wt.% NaCl solution similar to the seawater environment to evaluate the corrosion resistance properties. Through the surface shape analysis test by SEM and XRD, it was found that the Zn coating was porous and needle-shaped, so the penetration of the electrolyte was easy, and thus the corrosion rate was rapid. On the other hand, the Zn-15Al coating had a uniform and dense shape and was shown to suppress corrosion.