Thermal Conductivity of Plasma‐Sprayed Monolithic and Multilayer Coatings of Alumina and Yttria‐Stabilized Zirconia

Ravichandran, K.; An, Kyong Jun; Dutton, R.; Semiatin, S. L.

doi:10.1111/j.1151-2916.1999.tb01816.x

Cited by 91 publications

(32 citation statements)

References 20 publications

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“…6,9) Assessment of the Thermal Conductivity of Yttria-Stabilized Zirconia Coatingwork as well as that of plasma sprayed ZrO 2 measured by laser flash method from literature. 10,11) The effective thermal conductivity of 8YSZ of the present experiments varied from 0.11 to 0.16 W/mK, which is much smaller than that measured by laser flash method in literature by a factor of 0.10.2, though the specimens have the same microstructure made by plasma spray deposition.…”

Section: Resultsmentioning

confidence: 51%

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Assessment of the Thermal Conductivity of Yttria-Stabilized Zirconia Coating

2014

Mater. Trans.

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The approach is based on an experimental set-up in which coated surface of the specimen was exposed to high temperature environment and inner metal surface was cooled by flowing air, simulating the actual gas turbine applications. The 8% yttria-stabilized zirconia coating was made by plasma spray method on a cylindrical specimen. This arrangement could be set-up in a laboratory. By measuring the overall thermal resistances of specimens, it has been shown that the thermal conductivity of the coating segment can be determined by the differences in thermal resistances of two specimens with and without coating. The objective of the present work is to extract the thermal conductivity of the thermal barrier coating under the condition that is nearly the same as the actual application. The effective thermal conductivities of coatings found to be 0.11 to 0.16 W/mK, while those measured by laser flash method in literature varied from 1 to 1.4 W/mK.

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Section: Resultsmentioning

confidence: 51%

“…By assuming 11.4 W/mK of thermal conductivity determined by laser flash method as literature, 9,11) the thermal resistance of 2 mm coating layer alone, R 8YSZ , was 0.85 K/W from the following eq. (7), which suggests that its contribution was only about 6% to overall thermal resistance of 14.82 K/W at 1000°C of furnace temperature.…”

Section: Resultsmentioning

confidence: 99%

Assessment of the Thermal Conductivity of Yttria-Stabilized Zirconia Coating

2014

Mater. Trans.

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“…Thermal barrier coatings (TBC) have been established as the surface engineering method of choice for hightemperature applications owing to their excellent thermal, mechanical, and chemical properties (Ref [1][2][3][4]. A typical TBC system consists of a ceramic layer on top of a relatively thinner bond coat (BC).…”

Section: Introductionmentioning

confidence: 99%

Thermal Cycling of Yttria-Stabilized Zirconia-Coated Hot Work Tool Steel

Birol

2011

J Therm Spray Tech

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Thermal fatigue performance of yttria-stabilized zirconia-coated hot work tool steel was investigated under conditions encountered by thixoforming dies in semi-solid processing of steels. The thermal barrier effect of the YSZ coating was evident from the relatively smaller and more uniform temperature gradients set up across the section of the sample, which in turn, had a direct impact on the magnitude of thermal stresses generated at the surface of the tool steel. In spite of some thermal expansion mismatch with the substrate tool steel and occasional discontinuous thermally grown oxides along the splat boundaries and between the BC and TC, the YSZ coating survived thermal cycling under steel thixoforming conditions for over 12,000 cycles with no evidence of debonding and spallation. This is a nearly ten-fold increase in thermal fatigue life with respect to the uncoated counterpart. An increasingly dense YSZ layer and the toughening linked with the tetragonal to monoclinic ZrO 2 phase transformation are credited for the remarkable performance of the YSZ-coating. It is fair to conclude that the YSZ coating offers adequate protection for the underlying tool steel, which without YSZ coating, suffers severe oxidation after only several hundred cycles and extensive cracking after 1000 cycles.

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“…The basis of this model (in which the proportionate area of a splat in contact with its neighbours is an important parameter) is illustrated in figure 5. Some predictions are shown in figure 6b, based on conductivity data for the two constituents shown in figure 6a, and compared with experimental data (Pawlowski & Fauchais 1992;Ravichandran et al 1999;Zhu & Miller 2000;Trice et al 2002). The precise conductivity of air in the inter-splat pores is predicted to have a significant effect on the overall conductivity, depending on the inter-splat bridge area.…”

Section: Illustrative Case Historiesmentioning

confidence: 99%

Porous materials for thermal management under extreme conditions

Clyne

Golosnoy

Tan

et al. 2005

Phil. Trans. R. Soc. A.

120

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A brief analysis is presented of how heat transfer takes place in porous materials of various types. The emphasis is on materials able to withstand extremes of temperature, gas pressure, irradiation, etc., i.e. metals and ceramics, rather than polymers. A primary aim is commonly to maximize either the thermal resistance (i.e. provide insulation) or the rate of thermal equilibration between the material and a fluid passing through it (i.e. to facilitate heat exchange). The main structural characteristics concern porosity (void content), anisotropy, pore connectivity and scale. The effect of scale is complex, since the permeability decreases as the structure is refined, but the interfacial area for fluid-solid heat exchange is, thereby, raised. The durability of the pore structure may also be an issue, with a possible disadvantage of finer scale structures being poor microstructural stability under service conditions. Finally, good mechanical properties may be required, since the development of thermal gradients, high fluid fluxes, etc. can generate substantial levels of stress. There are, thus, some complex interplays between service conditions, pore architecture/scale, fluid permeation characteristics, convective heat flow, thermal conduction and radiative heat transfer. Such interplays are illustrated with reference to three examples: (i) a thermal barrier coating in a gas turbine engine; (ii) a Space Shuttle tile; and (iii) a Stirling engine heat exchanger. Highly porous, permeable materials are often made by bonding fibres together into a network structure and much of the analysis presented here is oriented towards such materials.

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Thermal Conductivity of Plasma‐Sprayed Monolithic and Multilayer Coatings of Alumina and Yttria‐Stabilized Zirconia

Cited by 91 publications

References 20 publications

Assessment of the Thermal Conductivity of Yttria-Stabilized Zirconia Coating

Assessment of the Thermal Conductivity of Yttria-Stabilized Zirconia Coating

Thermal Cycling of Yttria-Stabilized Zirconia-Coated Hot Work Tool Steel

Porous materials for thermal management under extreme conditions

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