• Title, Summary, Keyword: Thermal Barrier Coating

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FGM-TBC의 열충격 특성에 미치는 진공 플라즈마 용사조건의 영향

  • Jeong, Yeong-Hun;Byeon, Eung-Seon;Nam, Uk-Hui;Lee, Gu-Hyeon;Gang, Jeong-Yun
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.524-524
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    • 2012
  • Thermal Barrier Coating (TBC)은 미사일, 로켓발사체와 같이 고온에 노출되는 장비를 열로부터 보호하기 위한 코팅이다. 일반적인 Thermal Barrier Coating (TBC)은 모재와 코팅층간의 낮은 접합력과 높은 열충격으로 인한 박리가 많이 나타난다. 그래서 접합력을 높이고, 열충격을 줄이기 위해 모재와 코팅층 사이에 본드코팅층을 만든 Duplex - Thermal Barrier Coating (Duplex-TBC)이 개발되었다. 그러나 Duplex - Thermal Barrier Coating (Duplex-TBC)은 금속재료인 본드코팅층과 세라믹재료인 탑코팅층 사이에서 박리가 많이 발생한다. 이러한 문제점을 해결하기 위해 두 가지 분말을 동시에 코팅하여 본드코팅과 탑코팅의 경계가 없는 Functional Gradient Material - Thermal Barrier Coating (FGM-TBC)의 연구가 필요하다. 본 연구에서는 Functional Gradient Material - Thermal Barrier Coating (FGM-TBC)의 열충격 특성에 미치는 진공 플라즈마 용사 조건의 영향을 조사하였다. Functional Gradient Material - Thermal Barrier Coating (FGM-TBC)는 진공 플라즈마 용사장치를 사용하여 Cu-Cr 합금위에 코팅하였다. 거리, Carrier gas flow, 그리고 챔버 내부의 압력을 달리하여 제조하였다. 사용한 분말은 본드코팅용으로 Amdry 962와 내열 세라믹코팅을 위해 204NS를 사용하였고, 각각 분말 공급조건을 조절하여 두 분말의 비율을 달리하였다. 제조한 Functional Gradient Material - Thermal Barrier Coating (FGM-TBC) 코팅은 전기로에서 50분간 가열한 후, 수조에서 10분간 냉각하는 열충격 실험을 통해 열차폐 성능을 평가 하였다. 이러한 과정에서 진공 플라즈마 용사 조건 및 FGM 조성과 비율이 내열충격 특성에 미치는 영향을 미세조직학적 관점에서 고찰하였다.

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Top Coating Design Technique for Thermal Barrier of Gas Turbine (가스터빈의 열차폐용 탑코팅 설계기술)

  • Koo, Jae-Mean;Lee, Si-Young;Seok, Chang-Sung
    • Journal of the Korean Society for Precision Engineering
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    • v.30 no.8
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    • pp.802-808
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    • 2013
  • Thermal barrier coating (TBC) is used to protect substrates and extend the operating life of gas turbines in power plant and aeronautical applications. The major causes of failure of such coatings is spallation, which results from thermal stress due to a thermal expansion coefficient mismatch between the top coating and the bond coating layers. In this paper, the effects of the material properties and the thickness of the top coating layer on thermal stresses were evaluated using the finite element method and the equation for the thermal expansion coefficient mismatch stress. In addition, we investigated a design technique for the top coating whereby thermal resistance is exploited.

Effects of Composition, Structure Design, and Coating Thickness of Thermal Barrier Coatings on Thermal Barrier Performance

  • Jung, Sung-Hoon;Jeon, Soo-Hyeok;Lee, Je-Hyun;Jung, Yeon-Gil;Kim, In-Soo;Choi, Baig-Gyu
    • Journal of the Korean Ceramic Society
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    • v.53 no.6
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    • pp.689-699
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    • 2016
  • The effects of composition, structure design, and coating thickness of thermal barrier coating (TBC) on thermal barrier performance were investigated by measuring the temperature differences of TBC samples. TBCs with the thin and thick top coats were used for these studies, including TBCs with rare-earth (Gd, Yb, and La) compositions. The thermal barrier performance was enhanced with increasing the thickness of top coat even for thin TBCs, indicating that the thermal barrier performance was commensurate to the thickness of top coat. On the other hand, the bi-layered TBC, which was prepared with Yb-Gd-YSZ feedstock powder, with the buffer layer of high purity 8YSZ showed a better thermal barrier performance than that of regular purity 8YSZ. The interfaces in the bi-layered TBCs had a decisive effect on the thermal barrier performance, showing the performance enhanced with increasing numbers of interfaces. However, a new structural design and an additional process should be considered to reduce stress concentrations and to ensure interface stability, respectively, for improving thermal durability in the multi-layered TBCs.

Design Technique for Improving the Durability of Top Coating for Thermal Barrier of Gas Turbine (가스터빈의 열차폐용 탑코팅의 내구성 향상 설계기술)

  • Koo, Jae-Mean;Seok, Chang-Sung
    • Journal of the Korean Society for Precision Engineering
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    • v.31 no.1
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    • pp.15-20
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    • 2014
  • Thermal barrier coating (TBC) is used to protect the substrate and extend the operating life of the gas turbine for a power plant and an aircraft. The major cause of failure of such a coating is the spallation of coating, and it results from the thermal stress between top coating and bond coating. To improve the durability of TBC system, the dense vertical cracked (DVC) coating method to insert vertical cracks is applied to a gas turbine blade. In this study, a criterion for the design of vertical crack in the DVC coating was presented using the finite element analysis.

Mechanical Properties of Zirconia-Based Ceramic Materials for Thermal Barrier Coating (열차폐 코팅을 위한 지르코니아계 세라믹 소재의 기계적 특성)

  • Jung, Kyu-Ick;Kim, Tae-Woo;Paik, Ungyu;Lee, Kee-Sung
    • Journal of the Korean Ceramic Society
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    • v.43 no.8
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    • pp.498-503
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    • 2006
  • A gas turbine blade with thermal barrier ceramic coating is operated at high temperature to increase engine efficiency. Recently, thermal barrier characteristics have been improved by advanced coating technology through microstructure control and increase of adhesion force of the coating layer. More advanced coating materials, rare earth zircon ate ceramics have been studied for replacing YSZ coatings as thermal barrier coatings. In this study, $La_2O_3,\;HfO_2,\;CeO_2,\;Gd_2O_3$ and pure or yttria stabilized zirconia were prepared. Microstructure analysis and the evaluation of mechanical properties such as Hertzian indentation and hardness test were performed.

A Study on Acoustic Emission Characteristics through the Cyclic Thermal Test of Thermal Barrier Coating by Plasma Spray Process (플라즈마 용사법에 의한 열차폐 코팅의 열피로에 따른 AE신호 특성 연구)

  • Park J.H.;Lee K.H.;Ye K.H.;Kim S.T.;Jeon C.H.;Kim J.S.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.1349-1352
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    • 2005
  • This paper is to investigate a defect for thermal barrier coating layers by acoustic emission method in 4-point bending test. The two-layer thermal barrier coating is composed of $150\mu{m}\;CoNiCrAlY\;bond\;coating\;by\;vacuum\;plasma\;spray(VPS)\;process\;and\;250\mu{m}\;ZrO_2-8wt%Y_2O_3$ ceramic coating layer by air plasma spray(APS) process on Inconel-718. The specimen prepared by cyclic thermal test(500, 1000, 2000cycle) at $1050^{\circ}C$ The AE monitoring system is composed of PICO type sensor, a wide band pre-amplifier(40dB), PC and AE DSP(16/32 PAC) board. The AE event, amplitude, Cumulative energy and count of coating specimens is evaluated according to cyclic thermal test.

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Evaluation of Degradation Characteristics of Thermal Barrier Coating on Gas Turbine Blades

  • Jung, Yongchan;Kim, Mintae;Lee, Juhyeung;Ahn, Jamin;Kim, Kihong
    • KEPCO Journal on Electric Power and Energy
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    • v.2 no.2
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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.