• KEPCO Journal on Electric Power and Energy
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• 제2권2호
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• pp.273-278
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• 2016

In order to evaluate the lifespan of high-temperature parts with thermal barrier coating in gas turbines used for power generation, this study was performed on an 80 MW-class gas turbine exceeding 24 k equivalent operating hours. Degradation characteristics were evaluated by analyzing the YSZ (Yttria Stabilized Zirconia) top coat, which serves as the thermal barrier coating layer, the NiCrAlY bond coat, and interface layers. Microstructural analysis of the top, middle, and bottom sections showed that Thermal Growth Oxide (TGO) growth, Cr precipitate growth within the bond coat layer, and formation of diffusion layer occur actively in high-temperature sections. These microstructural changes were consistent with damaged areas of the thermal barrier coating layer observed at the surface of the used blade. The distribution of Cr precipitates within the bond coat layer, in addition to the thickness of TGO, is regarded as a key indicator in the evaluation of degradation characteristics.

• 한국연소학회지
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• 제16권1호
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• pp.58-65
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• 2011

Thermal spray technology has been used in many industrial application. Especially, thermal spray coating have been employed with the purposes of achieving better resistances in abrasion, heat and corrosion. In the previous studies on the thermal spray coating, thermal spray characteristics from the perspective of combustion engineering have not been investigated sufficiently, while the material characteristics of the coated substrates have been investigated widely. In this study, the effect of spray particles on the flame behavior was experimentally investigated. The amount of the injected particles was measured using the light scattering method and the temperature of the particles was estimated using a two-color method. Various flame-spray interactions were observed and it was found that the high temperature zone near the flame is elongated by particles density. Based on these results, the applicability of the light scattering method and the two-color method was discussed.

• Corrosion Science and Technology
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• 제15권6호
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• pp.259-264
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• 2016

With a specially designed electrochemical cell, the changes in impedance behavior for Inconel 600 and aluminide diffusion coatings under molten sulfate film with thermal cycles (from $800^{\circ}C$ to $350^{\circ}C$) were monitored with electrochemical impedance measurements. It was found that corrosion resistance for both materials increased with lower temperatures. At the same time, the state of molten salt was also monitored successfully by measuring the changes in impedance at high frequency, which generally represents the resistance of molten salt itself. After two thermal cycles, both Inconel 600 and aluminide diffusion coatings showed excellent corrosion resistance. The results from SEM observation and EDS analysis correlated well with the results obtained by electrochemical impedance measurements. It is concluded that electrochemical impedance is very useful for monitoring the corrosion resistance of materials under molten salt film conditions even with thermal cycles.

• 한국태양에너지학회 논문집
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• 제35권4호
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• pp.9-15
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• 2015

Black cobalt solar selective coatings were prepared by using an electroplating method. The changes in the optical properties of the black cobalt selective coating due to thermal degradation were analyzed by using the Auger electron spectroscopy (AES) and spectrophotometer. The black cobalt selective coating was prepared on a copper substrate by using a synthesized electrolyte with $CoCl_2$ and KSCN at a current density of ${\sim}0.5A/dm^2$ for 45s ~ 60s. Its optical properties were a solar absorptance (${\alpha}$) of the order of 0.80 ~ 0.84 and a thermal emittance (${\epsilon}$) of 0.01. From the AES depth profile analysis of heated sample, thermal degradation of the black cobalt selective coating heated for 33 hours at temperature of $350^{\circ}C$ occurred primarily due to interdiffusion at interface of cobalt and copper substrate. This results were predictable that the ${\alpha}$ decreases due to the thermal oxidation and diffusion.

• 태양에너지
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• 제10권1호
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• pp.57-62
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• 1990

기판물질이 흑색크롬 선택흡수막의 열적 안정성에 미치는 영향이 RBS에 의해서 조사되었 다. 공기중 $450^{\circ}C$에서 24시간 열처리한 시료의 열퇴화를 연구하기 위해 선택흡수막의 기판물질로서는 구리, 니켈, 스텐레스스틸기판이 사용되었다. 기판물질 확산의 실험 결과가 논의되었으며 스텐레스스틸 기판위에 제작된 시로의 기판물질의 확산이 적게 일어났음을 알 수 있었다

• 한국재료학회지
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• 제8권6호
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• pp.505-512
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• 1998

플라즈마 용사법을이용하여 AISI 316 스테인레스 금속모재에 0.1mm 두께의 $NiCrAlCoY_{2}O_{3}$금속 결합층과 0.3mm 두께의 $ZrO_{2}(8wt%Y_{2}O_3$) 세라믹층으로 구성된 이층 단열코팅층을 제조하였다. 코팅층의 미세조직, 금속결합층의 산화를 고찰하였으며, $900^{\circ}C$에서 등은 시험과 열반복시험 후, 접합강도시험을 통하여 코팅층의 단사정 상은 열처리시간이 길어질수록 약간 증가하였다. 또한 비변태성 t'의 c/a는 용사상태에서 1.0099이였으며, 100시간 열처리 후에는 1.0115로 약간 증가하였다. 그리고 용사층의 접합강도는 열처리 시간이 길어질수록 감소하였다. 등온열처리 후에는 1.0115로 약간 증가하였다. 그리고 용사층 의 접합강도는 열처리 시간이 길어질수록 감소하였다. 등온열처리 후, 파괴는 주로 세라믹층에서 일어났으며, 반복 열처리되 시편에서는 10회 이후 대부분 금속결합층/세라믹층의 계면에서 일어났다.

• 한국표면공학회지
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• 제55권6호
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• pp.408-416
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• 2022

In this study, the effect of Au-Sn alloy coating on reliability of electrical contacts was investigated via comparison with Au-Co alloy coating. The results show that Au-Sn alloy exhibited lower contact resistance and higher solder spreadability than those of Au-Co alloy after thermal aging. In the case of Au-Co alloy plating, the underlying Ni element diffused into Au-Co layer to form Ni oxides on surface during thermal aging, leading to increased contact resistance and decreased solder spreadability. Meanwhile, for Au-Sn alloy plating, Au-Ni-Sn metallic compound was formed at the interface between Au-Sn layer and underlying Ni layer. This compound acted as a diffusion barrier, thereby inhibiting the diffusion of Ni to Au-Sn layer during thermal aging. Consequently, Au-Sn alloy layer showed better contact reliability than that of Au-Co alloy layer.

• 공업화학
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• 제28권6호
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• pp.691-695
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• 2017

본 연구에서는 알카라인 연료전지 환원극 가스확산층에 내열화학성이 우수한 초발수 성능을 부여하기 위하여 PDMS 코팅 공정을 최적화하였다. 성격이 상이한 두 개의 상용 가스확산층을 선택하였으며, 소재의 열적 안정성을 검토하여 코팅 온도를 최적화하고, PDMS 점도를 제어하여 코팅 균일성을 확보하고자 하였다. PDMS 전구체의 점도와 관계없이 $200^{\circ}C$ 부근에서 코팅하게 되면 모든 확산층 표면에서 높은 초발수 성능을 나타내었다. 가혹실험 조건에서 초발수 성능변화를 측정한 결과 1000 CS PDMS를 이용하여 28BC 가스확산층에 코팅한 경우가 가장 높은 내구성을 나타내었다.

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 1986년도 Priceedings Of The Third Korea-Japan Seminar On New Ceramics
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• pp.211-225
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• 1986

Silicon carbide coating has been studied using a graphite substrate, a mixture of tetramethylsilane and hydrogen or argon at deposition temperature (T) of 950 to $1200^{\circ}C$ total pressure of 20 to 50 torr and carrier gas flow rate of 0 to 901/h. Deposition kinetic study has shown that a transition, from a surface reaction limited process to a diffusion limited one, takes place near $1100^{\circ}C$. Deposition rate depends directly upon the experimental parameters. The influence of the main process parameters is also discussed to relate the physiochemical properties of the coating to the deposition conditions.

• 한국표면공학회지
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• 제23권3호
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• pp.173-182
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• 1990

In order to prevent the thermal and enviromenatal degradation of contact materials a nickel layer was plated as an undercoat of gold plating on the surface phosphorous bronze. The thickness of nikel and gold coating and chemical resistance of the coatings were measured at various conditions. Variation of morphology and chemical composition was studied by SEM, EDS and ESCA, respectively. Nickel layer was found to act as a thermal diffusion barrier and to retard the diffusion of copper from substrate to gold coating in the temperature $200^{\circ}C$~$400^{\circ}C$. below $200^{\circ}C$gold coated contacts showed a stable and low contanct resistance, while above $200^{\circ}C$ rapid diffusion of copper formed copper oxide on the surface layer and raised the contact resistance. With the nickel thinkness of abount 5$\mu$m as an undercoat the gold thinkness of $0.5\mu$m, showed satistactory (less than 1 m$\Omega$) contact resistance below 20$0^{\circ}C$ and corresponding gold thinkness increased to 1.0 m at $300^{\circ}C$~$400^{\circ}C$.