Properties and Performance of High-Purity Thermal Barrier Coatings

Xie, Liangde; Dorfman, Mitchell R.; Cipitria, Amaia; Paul, Shiladitya; Golosnoy, Igor O.; Clyne, T.W.

doi:10.1007/s11666-007-9079-7

Cited by 49 publications

(20 citation statements)

References 16 publications

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“…The spraying conditions, and coating microstructures, were similar to those reported elsewhere [31,[75][76][77]. The predictions shown were obtained using input data, and predictions from the sintering model, shown in Table I.…”

Section: Overall Conduction Through Tbcs -The "Two Flux Regimes" Analsupporting

confidence: 55%

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Heat Transfer Through Plasma-Sprayed Thermal Barrier Coatings in Gas Turbines: A Review of Recent Work

2009

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A review is presented of how heat transfer takes place in plasma sprayed (zirconia-based) thermal barrier coatings (TBCs) during operation of gas turbines. These characteristics of TBCs are naturally of central importance to their function. Current state-of-the-art TBCs have relatively high levels of porosity (~15%) and the pore architecture (ie its morphology, connectivity and scale) has a strong influence on the heat flow. Contributions from convective, conductive and radiative heat transfer are considered, under a range of operating conditions, and the characteristics are illustrated with experimental data and modelling predictions. In fact, convective heat flow within TBCs usually makes a negligible contribution to the overall heat transfer through the coating, although what might be described as convection can be important if there are gross through-thickness defects such as segmentation cracks. Radiative heat transfer, on the other hand, can be significant within TBCs, depending on temperature and radiation scattering lengths, which in turn are sensitive to the grain structure and the pore architecture. Under most conditions of current interest, conductive heat transfer is largely predominant. However, it is not only conduction through solid ceramic that is important. Depending on the pore architecture, conduction through gas in the pores can play a significant role, particularly at the high gas pressures typically acting in gas turbines (although rarely applied in laboratory measurements of conductivity). The durability of the pore structure under service conditions is also of importance, and this review covers some recent work on how the pore architecture, and hence the conductivity, is affected by sintering phenomena. Some information is presented concerning the areas in which research and development work needs to be focussed if improvements in coating performance are to be achieved.

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Section: Overall Conduction Through Tbcs -The "Two Flux Regimes" Analsupporting

confidence: 55%

“…In fact, high purity specimens contain ~30% of cubic phase and <~1% monoclinic phase [75], even after 100 h at 1400˚C. In fact, the difference between the conductivities of the tetragonal and cubic phases in this system is relatively small [46,47] and can be neglected for most purposes.…”

Section: Predicted Changes In Conductivitymentioning

confidence: 99%

Heat Transfer Through Plasma-Sprayed Thermal Barrier Coatings in Gas Turbines: A Review of Recent Work

2009

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“…Both the intersplat pores and intrasplat cracks might be healed up, leading to significant stiffening of the top coat. This has a detrimental effect on the strain tolerance of top coat . In addition, the sintering of top coat also leads to an increase in thermal conductivity, resulting in distinct degradation on the thermal barrier performance …”

Section: Introductionmentioning

confidence: 99%

Sintering‐induced delamination of thermal barrier coatings by gradient thermal cyclic test

et al. 2017

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Lifetime is crucial to the application of advanced thermal barrier coatings (TBCs), and proper lifetime evaluation methods should be developed to predict the service lifetime of TBCs precisely and efficiently. In this study, plasma‐sprayed YSZ TBCs were subjected to gradient thermal cyclic tests under different surface temperatures, with the aim of elucidating the correlation between the coating surface temperature and the thermal cyclic lifetime. Results showed that the thermal cyclic lifetime of TBCs decreased with the increasing of surface temperatures. However, the failure modes of these TBCs subjected to thermal cyclic tests were irrespective of different surface/BC temperatures, that is, sintering‐induced delamination of the top coat. The thickness of thermally grown oxide (TGO) was significantly less than the critical TGO thickness to result in the failure of TBCs through the delamination of top coat. There was no phase transformation of the top coat after failure. In contrast, in the case concerning the top coat surface of the failure specimens, the elastic modulus and microhardness increased to a comparable level due to sintering despite of the various thermal cyclic conditions. Consequently, it is conclusive that the failure of TBCs subjected to gradient thermal cyclic test was primarily induced by sintering during high‐temperature exposure. A delamination model with multilayer splats was developed to assist in understanding the failure mechanism of TBCs through sintering‐induced delamination of the top coat. Based on the above‐described results, this study should aid in facilitating the lifetime evaluation of the TBCs, which are on active service at relatively lower temperatures, by an accelerated thermal cyclic test at higher temperatures in laboratory conditions.

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“…As a result, the accommodation of external stress occurs more extensively in PMMA and dentin. The plasticity of the plasma spraying aluminum oxide is caused by its porosity, insomuch as the plasticity of compacted alumina is almost zero [8]. Human dentin, which is a complicated hierarchic structure, possesses the high porosity, too [9].…”

Section: Discussionmentioning

confidence: 99%