• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제33회 춘계학술대회 개최
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• pp.42-48
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• 2001

Chromium carbides have the excellent wear properties as transition metal carbides. Their tribological applications were studied recently. The nano-sized ceramic could enhance the mechanical and electronical properties of materials. In this study, it was observed to test the wear of the coated surface of nano-sized chromium carbides. The nano-sized chromium carbides were produced by sol-gel processing. Coating surface of produced powders was obtained front plasma spraying. Wear test of coating surface was held increasing temperature. The friction coefficient and the wear loss were testified in dry environment. And the worn surfaces were analyzed by XRD and SEM.

• 한국분말재료학회지
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• 제19권5호
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• pp.348-355
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• 2012

Cold spray deposition using Titanium powder was carried out to investigate the effects of powder morphology and powder preheating on the coating properties such as porosity and hardness. The in-flight particle velocity of Ti powder in cold spray process was directly measured using the PIV (particle image velocimetry) equipment. Two types of powders (spherical and irregular ones) were used to manufacture cold sprayed coating layer. The results showed that the irregular morphology particle appeared higher in-flight particle velocity than that of the spherical one under the same process condition. The coating layer using irregular morphology powder represented lower porosity level and higher hardness. Two different preheating conditions (no preheating and preheating at $500^{\circ}C$) were used in the process of cold spraying. The porosity decreased and the hardness increased by conducting preheating at $500^{\circ}C$. It was found that the coating properties using different preheating conditions were dependent not on the particle velocity but on the deformation temperature of particle. The deposition mechanism of particles in cold spray process was also discussed based on the experimental results of in flight-particle velocity.

• 대한기계학회논문집A
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• 제34권4호
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• pp.475-480
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• 2010

가스터빈 블레이드는 터빈 가동 시 발생하는 고온화염으로부터 블레이드를 보호하고, 구조물의 표면 온도를 안전한 수준으로 낮추기 위하여 블레이드 표면에 열차폐 코팅(TBC; Thermal barrier coating)을 하여 사용하고 있다. 본 논문에서는 가스터빈 1단 블레이드에 적용되는 코팅 방식을 이용하여 코인형 시험편을 제작하였고 열화 온도 및 유지 시간의 변화에 따른 코팅 계면 산화물의 성장 거동을 분석하였다. 코팅 단면에 대하여 코팅 계면 산화물의 두께와 마이크로 비커스 경도를 측정하여 열화 특성을 평가 하였다. 또한 성분분석을 통하여 미세조직의 변화를 관찰함으로써 열차폐 코팅의 열적 열화특성을 평가하였다.

• 한국재료학회지
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• 제30권7호
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• pp.350-358
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• 2020

A variety of composite powders having different aluminum and carbon contents are prepared using various organic solvents having different amounts of carbon atoms in unit volume as ball milling agents for titanium and aluminum ball milling. The effects of substrate temperature and post-heat treatment on the texture and hardness of the coating are investigated by spraying with this reduced pressure plasma spray. The aluminum part of the composite powder evaporates during spraying, so that the film aluminum content is 30.9 mass%~37.4 mass% and the carbon content is 0.64 mass%~1.69 mass%. The main constituent phase of the coating formed on the water-cooled substrate is a non-planar α₂ phase, obtained by supersaturated carbon regardless of the alloy composition. When these films are heat-treated at 1123 K, the main constituent phase becomes γ phase, and fine Ti₂AlC precipitates to increase the film hardness. However, when heat treatment is performed at a higher temperature, the hardness is lowered. The main constitutional phase of the coating formed on the preheated substrate is an equilibrium gamma phase, and fine Ti₂AlC precipitates. The hardness of this coating is much higher than the hardness of the coating in the sprayed state formed on the water-cooled substrate. When hot pressing is applied to the coating, the porosity decreases but hardness also decreases because Ti₂AlC grows. The amount of Ti₂AlC in the hot-pressed film is 4.9 vol% to 15.3 vol%, depending on the carbon content of the film.

• 한국표면공학회지
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• 제46권5호
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• pp.181-186
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• 2013

We performed plasma spraying for 2001 (Bi:Cu = 2:1), 0212 (Sr:Ca:Cu = 2:1:2) oxide powders. $Bi_2Sr_2CaCu_2Ox$ (2212) superconductor has been prepared by PMP-AT (partial melting process-annealing treatment). The 2212 phase is synthesized between Sr-Ca-Cu oxide coating layer (0212) and Bi-Cu oxide coating layer (2001) by movement of partial melted Bi on 2001 layer and the diffusion reaction (Cu, Sr, Ca) after PMP-AT. There are two different coating layers on joining process. The one is ABAB coating layers and the other is BAAB coating layers by arrangement of 2001 (A), 0212 (B) layers. We performed heat treatment these two different coating layers processes under same PMP-AT conditions. We obtained Bi-2212 superconducting layers at each experimental condition, and the result of MPMS, the critical temperature was showed about 78 K. But the microstructure images and result of EDS as each experimental variable were showed about the qualitatively different Bi-2212 superconducting phases. We also deduced the generation mechanism of Bi-2212 superconducting layer as a result of these experimental data, microstruc ture images, EDS data and phase diagram.

• 대한금속재료학회지
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• 제47권11호
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• pp.728-733
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• 2009

Cu based amorphous ($Cu_{54}Zr_{22}Ti_{18}Ni_{6}$) powders were deposited onto Al 6061 substrates by cold spray process with different powder preheating temperatures (below glass transition temperature: $350^{\circ}C$, near glass transition temperature: $430^{\circ}C$ and near crystallization temperature: $500^{\circ}C$). The microstructure and macroscopic properties (hardness, wear and corrosion) of Cu based amorphous coating layers were also investigated. X-ray diffraction results showed that cold sprayed Cu based amorphous coating layers of $300{\sim}350{\mu}m$ thickness could be well manufactured regardless of powder preheating temperature. Porosity measurements revealed that the coating layers of $430^{\circ}C$ and $500^{\circ}C$ preheating temperature conditions had lower porosity contents (0.88%, 0.93%) than that of the $350^{\circ}C$ preheating condition (4.87%). Hardness was measured as 374.8 Hv ($350^{\circ}C$), 436.3 Hv ($430^{\circ}C$) and 455.4 Hv ($500^{\circ}C$) for the Cu based amorphous coating layers, respectively. The results of the suga test for the wear resistance property also corresponded well to the hardness results. The critical anodic current density ($i_{c}$) according to powder preheating temperature conditions of $430^{\circ}C$, $500^{\circ}C$ was lower than that of the sample preheated at $350^{\circ}C$, respectively. The higher hardness, wear and corrosion resistances of the preheating conditions of near $T_{g}$ and $T_{x}$, compared to the properties of below $T_{g}$, could be well explained by the lower porosity of coating layer.

• 한국건축시공학회지
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• 제23권5호
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• pp.559-570
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• 2023

건설산업에서 사용되는 구조용 강재의 부식은 산업화로 인해 많은 공격적인 이온이 내포된 대기 환경에서 증가추세에 있다. 따라서 본 연구에서는 아크 및 플라즈마 아크용사로 Al 코팅을 용착하여 Cl^-와 CO₃^2-같은 공격적인 이온을 다량 함유한 Society of Automotive Engineering(SAE) J2334 용액의 모사대기환경에서 그 효과를 비교하였다. 다양한 분석기법으로 코팅 특성과 부식 메커니즘을 고찰하였다. 플라즈마 아크용사로 용착된 Al 코팅은 밀도 있고 균일하면 층층이 적층이 잘 되었고 높은 부착력이 나타났다. 이 공법으로 용착된 Al 코팅을 SAE J2334 용액에 기간별로 침지하여 측정한 개회로전위(OCP)는 아크용사로 용착된 Al 코팅보다 더 양전성(electropositive)한 값을 보여주었다. 플라즈마 아크용사는 총 임피던스가 아크용사보다 높게 나타났다. SAE J2334 용액에 23일 침지하였을 때 플라즈마 아크용사 Al 코팅의 부식속도는 아크용사에 비해 20% 감소하였다.

• 한국분말재료학회지
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• 제30권5호
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• pp.415-423
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• 2023

With the increasing attention to environmental pollution caused by particulate matter globally, the automotive industry has also become increasingly interested in particulate matter, especially particulate matter generated by automobile brake systems. Here, we designed a coating composition and analyzed its mechanical properties to reduce particulate matter generated by brake systems during braking of vehicles. We designed a composition to check the mechanical properties change by adding Cr₃C₂ and YSZ to the WC-Ni-Cr composite composition. Based on the designed composition, coating samples were manufactured, and the coating properties were analyzed by Vickers hardness and ball-on-disk tests. As a result of the experiments, we found that the hardness and friction coefficient of the coating increased as the amount of Cr₃C₂ added decreased. Furthermore, we found that the hardness of the coating layer decreased when YSZ was added at 20vol%, but the friction coefficient was higher than the composition with Cr₃C₂ addition.

• 한국분말재료학회지
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• 제23권1호
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• pp.15-20
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• 2016

Niobium is one of the most important and rarest metals, and is used in the electronic and energy industries. However, it's extremely high melting point and oxygen affinity limits the manufacture of Nb coating materials. Here, a Nb coating material is manufactured using a kinetic spray process followed by hot isotactic pressing to improve its properties. OM (optical microscope), XRD (X-ray diffraction), SEM (scanning electron microscopy), and Vickers hardness and EPMA (electron probe micro analyzer) tests are employed to investigate the macroscopic properties of the manufactured Nb materials. The powder used to manufacture the material has angular-shaped particles with an average particle size of $23.8{\mu}m$. The porosity and hardness of the manufactured Nb material are 0.18% and 221 Hv, respectively. Additional HIP is applied to the manufactured Nb material for 4 h under an Ar atmosphere after which the porosity decreases to 0.08% and the hardness increases to 253 Hv. Phase analysis after the HIP shows the presence of only pure Nb. The study also discusses the possibility of using the manufactured Nb material as a sputtering target.

• 대한기계학회논문집A
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• 제20권10호
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• pp.3234-3242
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• 1996

This paper describes experimental results of modified small punch( MSP) test conducted to evaluate the fracure characteristics and mechanical properties of plasma sparayed zirconia ($ZrO_2$ stabilized with 8wt. % $Y_20_3$ : YSZ) NiCrAlY composite. The mixing ratios of YSZ/NiCrAlY were 0/100, 25/75, 50/50, 100/0 v.%. Test temperatures ranged from 293K to 1473K. This study is directed at development of thermal barrrier coating(TBC) system with superior heat resistance and mechanical properties. The microstructure and fracture process of the composite were examined by SEM and AE method. The mechanical properties of 100% YSZ were nearly independent of the temperatures tested in this study. In contrast, the NiCrAlY-containing composites showed a significant decrease of the mechanical properties above 1273K, showing a ductile- brittle transition behavior up to the temperature. Furthermore, it can seen that 25% YSZ/75% NiCrAlY composite gave the highest fracure strength and fracture energy among the mixing ratio tested over the temperature range.