• Title/Summary/Keyword: top coating

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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.

Studies on the multi-layered coated paper(I) - The effect of pre-coated layer formulation on top coated layer properties - (다층 도공지에 관한 연구(I) - 프리코팅층의 안료배합이 탑층의 물성에 미치는 영향 -)

  • Lee, Myoung-Seok;Kim, Sun-Kyung;Cho, Byoung-Uk;Lee, Yong-Kyu
    • Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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    • 2011.04a
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    • pp.251-263
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    • 2011
  • This study was carried out in order to investigate the effect of pre-coating layer on top-coating layer. The coated paper with five different formulations were prepared. The properties of coated paper were measured and correlation between pre and top-coated layer was evaluated. Paper gloss was increased with addition of clay and GCC that has smaller particle size. Roughness was decreased with using smaller particle GCC, clay and talc. The highest thickness was obtained with talc. Brightness and whiteness of pre-coated layer were affected to top-coated layer. GCC 60 shows the highest and ununiform water adsorption during 1sec. The adsorption was higher with increasing coated weight. Talc shows the excellent water adsorption properties due to its wettability. These results indicate that final printability and properties of top coating layer can be controlled with adjusting pre-coating layer.

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Acoustic Emission Characteristics of Ceramic Coated Steel by Plasma Spraying (플래즈머용사에 의한 세라믹 코팅 강재의 음향방출 특성)

  • Kim, G.S.
    • 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.

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Corrosion Resistance of Non-Chrome Magni 565 Coating and Characteristics of Its Coating Film (Non-Chrome Magni 565 코팅 피막의 특성과 내식성)

  • Kim, Sang-Su;Jeong, Byeong-Ho;Mun, Myeong-Jun;Kim, Mu-Gil
    • Journal of the Korean Society for Heat Treatment
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    • v.19 no.4
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    • pp.200-207
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    • 2006
  • In addition to the basic properties of the base and top coating agents, corrosion resistance of non-chrome magni 565 coating and characteristics of coating film when coated to steel substrate were studied. The system had a good wettability at room temperature. Moreover, both the contact angle and surface tension were affected little by the viscosity of coating agent and surface roughness of the steel substrate. And the samples coated with optimal conditions showed a great corrosion resistance in salt spray test with 1500 hours or longer of initial appearance time of rust. The coating film was composed of overlapping layer of zinc and aluminium flakes, and the thickness of base coat increased with an increase of base coat viscosity. Based on the C-F peaks of 1,1-Difluoroethaen homo-polymer, it was thought that the base coat was an inorganic polymer bond layer. Meanwhile, the top coat showed C-F peaks of polytetrafluoroethylene with C-H peaks of phenol in FT-IR analysis. From the lower weight loss of base coat in TG analysis, it was thought that cross linking density of base coat was larger than that of top coat. It was thought that the small exothermic reactions observed in DSC curves were due to the thermosetting resins contained in the coating agents. Compared to the non-coated specimen, the coated sample showed more higher polarization resistance and corrosion potential with lower corrosion current density.

Precise ultrasonic coating and controlled release of sirolimus with biodegradable polymers for drug-eluting stent

  • Joung, Yoon Ki;Jang, Bu Nam;Kang, Jong Hee;Han, Dong Keun
    • Biomaterials and Biomechanics in Bioengineering
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    • v.1 no.1
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    • pp.13-25
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    • 2014
  • In the current study, a drug-eluting stent coated with biodegradable polymers and sirolimus was developed by using an ultrasonic nanocoater and characterized in aspects of surface smoothness and coating thickness. In addition, in vitro release profiles of sirolimus by changing top coating layer with different biodegradable polymers were investigated. Smooth surfaces with variable thickness could be fabricated by optimizing polymer concentration, flow rate, nozzle-tip distance, gas pressure, various solvents and ultrasonic power. Smooth surface could be generated by using volatile solvents (acetone, chloroform, and methylene chloride) or post-treating with solvent vapor. Coating thickness could be controlled by varying injection volume or polymer concentration, and higher concentration could reduce the coating time while obtaining the same thickness. The thickness measurement was the most effectively performed by a conventional cutting method among three different methods that were investigated in this study. Release profiles of sirolimus were effectively controlled by changing polymers for top layer. PLGA made the release rate 3 times faster than PDLLA and PLLA and all top layers prevented burst release at the initial phase of profiles. Our results will provide useful and informative knowledge for developing drug-eluting stents, especially coated with biodegradable polymers.

Lifetime Performance of EB-PVD Thermal Barrier Coatings with Coating Thickness in Cyclic Thermal Exposure

  • Lu, Zhe;Lee, Seoung Soo;Lee, Je-Hyun;Jung, Yeon-Gil
    • Korean Journal of Materials Research
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    • v.25 no.10
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    • pp.571-576
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    • 2015
  • The effects of coating thickness on the delamination and fracture behavior of thermal barrier coating (TBC) systems were investigated with cyclic flame thermal fatigue (FTF) and thermal shock (TS) tests. The top and bond coats of the TBCs were prepared by electron beam-physical vapor deposition and low pressure plasma spray methods, respectively, with a thickness ratio of 2:1 in the top and bond coats. The thicknesses of the top coat were 200 and $500{\mu}m$, and those of the bond coat were 100 and $250{\mu}m$. FTF tests were performed until 1140 cycles at a surface temperature of $1100^{\circ}C$ for a dwell time of 5 min. TS tests were also done until more than 50 % delamination or 1140 cycles with a dwell time of 60 min. After the FTF for 1140 cycles, the interface microstructures of each TBC exhibited a sound condition without cracking or delamination. In the TS, the TBCs of 200 and $500{\mu}m$ were fully delaminated (> 50 %) within 171 and 440 cycles, respectively. These results enabled us to control the thickness of TBC systems and to propose an efficient coating in protecting the substrate in cyclic thermal exposure environments.

Suppression of the surface nucleation of YBa$_2$Cu$_3$O$_7-y$ by CeO$_2$ coating of the top-seeded melt processed YBCO superconductors

  • Kim, Ho-Jin;Jun, Byung-Hyuk;Kim, Chan-Joong
    • Progress in Superconductivity and Cryogenics
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    • v.5 no.3
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    • pp.1-5
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    • 2003
  • The effect of CeO$_2$ coating on the surface nucleation of the top-seeded melt-growth processed YBCO superconductors was studied. It was effective that the coating of Y123 compact surfaces by CeO$_2$ powder suppressed the undesirable subsidiary YBa$_2$Cu$_3$O$_{7-y}$ (Y123) nucleation during melt processing. BaCeO$_3$ was formed in the CeO$_2$-coated layers, which might cause a CuO-excessive liquid at the partial melt stage of $Y_2$BaCuO$_{5}$(Y211) plus liquid, and thus the Y123 nucleation at the YBCO compact surfaces could be suppressed during the melt growth of Y123 grain. In addition, the CeO$_2$ refined the Y211 particles near the compact / coating interface. While the levitation forces of the top surfaces with and without CeO$_2$ coating were similar to each other, the levitation force of the interior of the CeO$_2$ coated sample was higher than that of the interior of the sample without CeO$_2$ coating, which was attributed to the suppression of subsidiary Y123 nucleation at the compact walls.s.s.

A Study on the Effects of the Thickness of Top Coat on the Thermal Stresses of a Sprayed Thermal Barrier Coating (용사 열차폐 코팅층의 두께가 열응력에 미치는 영향)

  • 김형남;양승한
    • Proceedings of the KWS Conference
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    • 2004.05a
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    • pp.223-225
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    • 2004
  • Based on the principle of complementary energy an analytical method is developed for determining thermal stress distribution in an thermal barrier coating. This method gives the stress distributions which satisfy the stress-free boundary conditions at the edge. Numerical examples are given in order to verify the method and to investigate the thickness effects of the ZrO$_2$-8wt%Y$_2$O$_3$ top coat on the integrity of thermal barrier coating consisted of IN738LC substrate and MCrAlY bond coat.

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A Study on Durability of Sprayed Coating Layer in the Molten Zn-0.2% Al Alloy Bath (아연-0.2%알루미늄합금 용융도금액 중에서 용사층의 내구성에 관한 연구)

  • 강태영;임병문;최장현;김영식
    • Journal of Welding and Joining
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    • v.19 no.5
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    • pp.512-519
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    • 2001
  • Sink roll has been used in molten Zn-0.2%Al alloy bath of continuous galvanizing line in sinking and stabilizing process of the steel strip in molten metal bath. In this process, although the scraper scraps off the sink roll surface, the dross compounds is builded up on the sink roll surface and the life time of the sink roll is shorten by the dross compounds. The present study was investigated the application of the spray coating layer on sink roll body for improving durability In molten Zn-0.2%Al alloy. Through the durability tests in molten Zn-0.2%Al alloy with various ceramic and cermet coating layer, the optimum bond and top coating material was obtained. As the results, the system of STS430F base metal, WC-l7Co bond and $ZrO_2-SiO_2$ top coating was clarified to be the best quality of durability in molten Zn-0.2%Al alloy.

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Effect of Coating of Liner Components with Oxidized Starch on Properties of Corrugated Box (산화전분 코팅에 의한 골판지 상자의 물성 변화)

  • 안병국;안원영
    • Journal of Korea Technical Association of The Pulp and Paper Industry
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    • v.31 no.3
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    • pp.47-53
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    • 1999
  • The effect of coating of liner components with oxidized starch on the properties of corrugated box was examined . Coating was carried out on liner components of B flute, single-wall corrugated board(SK180/S120/K200) , and corrugated box was made from the treated corrugated board. Box was made in a regular slotted container (RSC) style, and box compression strength was determined in the direction of top-to-bottom compression. The compression strength of box coated on outside liner component showed 15.4% improvement for 1.58g㎡ coating. On the other hand, the strength of box coated on outside liner component showed only 1.45% improvement for 1.41g/㎡ coating and 3.46% improvement for 2.32g/㎡ coating. Coating on inside liner component with oxidized starch at low coating weight more significantly improved box compression strength than coating on outside liner component, and the improvement was marked at the coating weight of 1.5-2.5g/㎡. In estimating top-to-bottom box compression strength, the experimental values were closer to the calculated values from McKee's equation suing edgewise compression strength of the combined board measured by column crush test than those from Kellicutt's equation using compression strength of component paperboards measured by ring crush test.

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