• 한국세라믹학회지
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• 제39권1호
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• pp.79-85
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• 2002

플라즈마 용사코팅법을 이용하여 산화몰리브덴이 첨가된 크로미아 용사코팅층을 제조하여 MoO$_3$첨가에 따른 마찰, 마멸특성을 조사하였다. 상온 마찰, 마멸특성에 대한 실험을 위하여 왕복동 마멸시험장치를 사용하였다. 마멸시험후 마멸면의 물리적 변화와 화학적 조성의 변화를 SEM와 XPS를 통하여 살펴보았다. 산화몰리브덴이 첨가된 코팅층에서 마찰계수의 감소를 관찰할 수 있었다. 그러나 마멸량의 경우 산화몰리브덴이 첨가되지않은 크로미아 코팅층에서 가장 낮은 값을 나타내었다. 산화몰리브덴이 첨가된 코팅의 마멸된 표면에 마탈, 마멸에 유리한 보호막의 형성이 광범위하게 일어남을 알 수 있었다. 이러한 보호막에 산화몰리브덴이 MoO$_3$의 형태로 존재하는 것을 XPS분석을 통하여 알 수 있었다. 보호막에 산화몰리브덴의 존재가 마찰계수를 감소시키는 것으로 생각된다.

• 한국재료학회지
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• 제9권4호
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• pp.428-433
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• 1999

본 연구는 $0.1~1.2\mu\textrm{m}$ 압도분포를 갖는 미세 $Al_2O_3$를 이용하여 플라츠마 용사한 후 상업용 용사분말(Metco 105)과 용사층의 특성을 비교하였다. 미세조직은 미세 $Al_2O_3$층이 상업용분말보다 더 치밀하였고 용샤층의 평균 표면조도 $(R_a)$는 미세 $Al_2O_3$의 경우에 $5.3\mu\textrm{m}$로 상업용 분말 $(R_a=8.2\mu\textrm{m})$ 보다 작은 값을 보였으며, 용사층 평균 splat 두께는 $1.4\mu\textrm{m}$ 였다. 또한 용샤층에는 많은 양의 부분 용융입자가 관찰되었다. XRD분석결과 두 분말 모두 용사층을 이루는 주된 상은 $\gamma-Al_2O_3$이였으며 $\alpha-Al_2O_3$도 관찰되었다. 용사층에 존재하는 $\alpha-Al_2O_3$의 분율은 미세 $Al_2O_3$층의 경우 8.39%. 상업용 $Al_2O_3$의 경우 13.79%이였다. 미세 경도 값은 두 분말에서 큰 차이를 보이지는 않았으나, 미세 $Al_2O_3$의 경우 큰 경도값 편차를 보였으며 따라서 미세 $Al_2O_3$층의 splat의 접합강도는 상업용 $Al_2O_3$보다 상대적으로 낮을 것으로 생각된다.

• 한국분말재료학회지
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• 제22권1호
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• pp.32-38
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• 2015

The effect of heat treatment environment on the microstructure and properties of tantalum coating layer manufactured by kinetic spraying was examined. Heat treatments are conducted for one hour at $800^{\circ}C$, $900^{\circ}C$, and $1000^{\circ}C$ in two different environments of vacuum and Ar gas. Evaluation of microstructure and physical properties are conducted. High density ${\alpha}$-tantalum single phase coating layer with a porosity of 0.04% and hardness of 550 Hv can be obtained. As heat treatment temperature increases, porosity identically decreases regardless of heat treatment environment (vacuum and Ar gas). Hardness of heat treated coating layer especially in Ar gas environment deceases from 550 Hv to 490 Hv with increasing heat treatment temperature. That in vacuum environment deceases from 550 Hv to 530 Hv. The boundary between particles became vague as heat treatment temperature increases. Oxygen distribution of tantalum coating layer is minute after heat treatment in vacuum environment than Ar gas environment.

• 한국분말재료학회지
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• 제23권1호
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• pp.8-14
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• 2016

A bulk-type Ta material is fabricated using the kinetic spray process and its microstructure and physical properties are investigated. Ta powder with an angular size in the range $9-37{\mu}m$ (purity 99.95%) is sprayed on a Cu plate to form a coating layer. As a result, ~7 mm-sized bulk-type high-density material capable of being used as a sputter material is fabricated. In order to assess the physical properties of the thick coating layer at different locations, the coating material is observed at three different locations (surface, center, and interface). Furthermore, a vacuum heat treatment is applied to the coating material to reduce the variation of physical properties at different locations of the coating material and improve the density. OM, Vickers hardness test, SEM, XRD, and EBSD are implemented for analyzing the microstructure and physical properties. The fabricated Ta coating material produces porosity of 0.11~0.12%, hardness of 311~327 Hv, and minor variations at different locations. In addition, a decrease in the porosity and hardness is observed at different locations upon heat treatment.

• 한국세라믹학회지
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• 제40권2호
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• pp.123-127
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• 2003

The effects of process parameters on coating formation and coating properties were investigated using a fused and crushed Ti $O_2$powder by the Taguchi method and L$_{9}$(3$^4$) orthogonal array. The Taguchi analysis was conducted through the results of the coating properties affected strongly by plasma spraying parameters and Ti $O_2$powder was sprayed on Ti-6Al-4V alloy substrate. The coating properties were characterized by thickness, microhardness, porosity and surface roughness using optical microscopy, image analyzer and surface roughness tester respectively. An observed optimum condition of plasma spraying process could be found for potential use as a bioceramic coating.

• 한국표면공학회지
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• 제29권2호
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• pp.81-92
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• 1996

The cementless fixation of bone ingrowth by porous coatings on artificial hip joint prostheses are replacing polymethylmethacrylate(PMMA) bone cement fixations. However, the major interests in the field of porous metal coating are environmental corrosivity accelerated by metal ion release, deterioration in the mechanical property of the coating, and the mechanical failure of the coatings as well as the substrate. Therefore, the selection of right materials for coatings and the development of porous coating techniques must be accomplished. Because of the existing problems in Ti and Ti alloys which are used extensively, this study is focused on the plasma spraying technique for coating on super stainless steel substrate. In order to determine the optimum conditions which satisfy the requirement for the porous coatings, under the plasma spraying, we selected the experimental parameters which extensively influenced on the characteristics of the coating through the pre-examination. Spray distance has been selected among 120, 160, and 200mm and primary gas flow rate among 70, 100, and 130 SCFH. Current and secondary gas($H_2$) flow rate was fixed at 400A, and 15 SCFH respectively. To understand the characteristics of the coatings, surface morphology, cross-sectional micro-structure, surface roughness, residual stress, and corrosion resistance were elucidated and the best conditions for the bone ingrowth improvement on artificial hip joint prostheses were found.

• 한국강구조학회 논문집
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• 제28권5호
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• pp.373-382
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• 2016

도장 또는 금속용사는 강구조물의 방식에 널리 사용되고 있으며, 금속용사와 도장의 복합방식법은 혹독한 부식환경하에 놓인 강구조물에 고내후성 피복방식법으로 적용되고 있다. 본 연구에서는 아연(Zn), 아연-알루미늄(ZnAl)합금, 알루미늄(Al), 알루미늄-마그네슘(AlMg)합금의 4종류 금속용사 후 실링 처리한 시편, 4종류 금속용사 후 중방식 도장한 시편과 도장만 실시한 시편을 대상으로 175일간의 ISO 20340 부식촉진실험을 실시하여, 각 방식법의 상대적인 내후성능을 비교, 검토하였다. 강재표면까지 도달하는 원형 및 선형 초기결함으로부터의 표면상태 변화 및 도막의 노화면적에 근거한 내후성능의 평가 결과, 금속용사 후 실링 처리한 시편의 경우에는 알루미늄(Al) 및 알루미늄-마그네슘(AlMg)금속용사 후 실링 처리한 시편이 가장 우수한 내후성능을 보였으며, 금속용사 후 도장을 실시한 금속용사와 도장의 복합방식법의 경우에는 아연(Zn)용사에 도장을 실시한 복합방식 시편이 가장 우수한 내후성능을 나타내었다.

• 대한금속재료학회지
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• 제46권3호
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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.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.921-924
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• 2004

This paper is to investigate a crack for plasma sprayed MCrAlY coated material by acoustic emission method in 4-point bending test. The CoNiCrAlY is coated on Inconel-718 by vacuum plasma spray process. Micro-hardness measurement was conducted by means of Micro Vickers-hardness indentor. The porosity of coating layer was measured using a SEM and Image Analyzer. AE monitoring system is composed of PICO type sensor, a wide band preamplifier(40dB), a PC and AE DSP(16/32 PAC) board. The AE count, Hit and energy of coating specimens is measured according to coating thickness.

• 한국분말재료학회지
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• 제6권3호
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• pp.224-230
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• 1999

Oxide powders of $Cr_2O_3 \;and\;Cr_2O_3+3{\%}TiO_2$ were prepared by spray drying, plasma densification and fused+crushed processes. The oxide coating layers were made by plasma spray and characterized by microstructure, hardness, adhesion strength and relative density. The optimum spray distance for the high quality coatings by spraying dried powders was found to be 9cm. A small amount addition of $TiO_2\;in\;Cr_2O_3$ powder significantly improved coating characteristics by lowering the melting point of powders. The hardness and relative density of coating layers of the plasma densified powders were comparable to fused and crushed powders, however, the adhesion strength was much higher in the former case.