Laser Thermal Gradient Testing and Fracture Mechanics Study of a Thermal Barrier Coating

Wu, Yingsang; Hsu, Pei‐feng; Yao, Wang; McCay, Mary Helen; Croy, D. Edward; Moreno, David; He, Lianghua; Wang, Chao; Zhang, Hongqi

doi:10.1007/s11666-019-00879-9

Cited by 9 publications

(11 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Other than the custom-made burner rig, there was a facility developed, and this was used in the study by Yingsang et al [65]. They used a high heat flux rig to simulate TBC in gas turbine working condition at the exposed temperature of 1150 • C with 950 • C cooling air.…”

Section: Thermal Cyclic Test Rigmentioning

confidence: 99%

“…TBC was tested under cyclic conditions either by using a custom-made test rig that was equipped with the cooling air system [58][59][60][61]65], that was not equipped with the cooling air system [68], or a commercial test rig that was not equipped with the cooling air system [62,64]. These showed that there are a number of studies have developed test rigs that are capable of simulating TBC-assisted cooling air system.…”

Section: Thermal Cyclic Test Rigmentioning

confidence: 99%

See 1 more Smart Citation

Test-Rig Simulation on Hybrid Thermal Barrier Coating Assisted with Cooling Air System for Advanced Gas Turbine under Prolonged Exposures—A Review

et al. 2021

View full text Add to dashboard Cite

Thermal barrier coating (TBC) and cooling air systems are among the technologies that have been introduced and applied in pursuing the extensive development of advanced gas turbine. TBC is used to protect the gas turbine components from the higher operating temperature of advanced gas turbine, whereas cooling air systems are applied to assist TBC in lowering the temperature exposure of protected surfaces. Generally, a gas turbine operates in three main operational modes, which are base load, peak load, and part peak load. TBC performance under these three operational modes has become essential to be studied, as it will provide the gas turbine owners not only with the behaviors and damage mechanism of TBC but also a TBC life prediction in a particular operating condition. For TBC under base load or so called steady-state condition, a number of studies have been reviewed and discussed. However, it has been found that most of the studies have been conducted without the assistance of a cooling air system, which does not simulate the TBC in advanced gas turbine completely. From this review, the studies on TBC-assisted cooling air system to simulate the advanced gas turbine operating conditions have also been summarized, which are limited to test rig simulations under thermal cyclic mode where thermal cyclic represents peak and part peak load conditions. The equipment used to simulate the gas turbine operating condition, test temperatures, and durations are parameters that have been taken into consideration under this review. Finally, a test rig that is capable of simulating both TBC and cooling air effects at a high operating temperature of advanced gas turbines for prolonged exposure under steady-state condition has been proposed to be developed.

show abstract

Section: Thermal Cyclic Test Rigmentioning

confidence: 99%

Section: Thermal Cyclic Test Rigmentioning

confidence: 99%

Test-Rig Simulation on Hybrid Thermal Barrier Coating Assisted with Cooling Air System for Advanced Gas Turbine under Prolonged Exposures—A Review

et al. 2021

View full text Add to dashboard Cite

show abstract

“…The TGO layer is mostly Al 2 O 3 and is the primary driver of the failure or delamination of the top coat due to mis-matched thermal expansion coefficients among the TGO, top coat, and the bond coat. 5 Better thermal radiation resistance in the top coat designs will be beneficial to lower the overall top coat temperature.…”

Section: Introductionmentioning

confidence: 99%

“…The higher overall temperature in the top coat also leads to higher bond coat temperature, which leads to faster growth of a thermally grown oxide (TGO) layer between the top coat and bond coat. The TGO layer is mostly Al 2 O 3 and is the primary driver of the failure or delamination of the top coat due to mis‐matched thermal expansion coefficients among the TGO, top coat, and the bond coat 5 . Better thermal radiation resistance in the top coat designs will be beneficial to lower the overall top coat temperature.…”

Section: Introductionmentioning

confidence: 99%

Thermal radiative properties of zirconium oxide films in the near‐infrared wavelengths

Wang

Hsu

2022

Int J Applied Ceramic Tech

Self Cite

View full text Add to dashboard Cite

Thermal barrier coatings (TBCs) using yttria‐stabilized zirconium dioxide (YSZ) are widely used in gas turbines to protect metal components against the high combustion product temperature. Increasing combustion temperature and pressure, radiative heat transfer becomes an essential portion of the overall heat transfer in TBCs. This necessitates a greater understanding of the thermal radiative properties of YSZ films, especially in the near‐infrared wavelength range. The commonly used Kubelka–Munk (KM) method in the radiative property reduction from the measured transmittance and reflectance spectra of YSZ films can incur inaccurate results when the coating optical thickness is not sufficiently large. The discrete ordinates method with the asymmetric spherical ring angular quadrature can solve the radiative transfer equation with good accuracy in optically thin media. Considering the solution accuracy and computational efficiency, a hybrid approach of combining the KM and discrete ordinate methods is used to invert radiative properties. The absorption and scattering coefficients of air plasma sprayed YSZ films are determined over the wavelength range from 1 to 2.6 μm at room temperature. Over this near‐infrared wavelength range, the scattering coefficient decreases with the increasing wavelength, and the absorption coefficient is very small overall.

show abstract

“…Once nucleated, the vertical cracks can relax the constraint on sintering and accelerate sintering locally. This further drives the growth of the vertical cracks, which propagate toward the interface and link up with horizontal defects, which in turn propagate parallel to the plane of the coating, leading to delamination and failure of the TBC, as observed in a laser thermal gradient test 8 . Understanding the formation of vertical cracks and how they couple with sintering is important to fully understand and prevent TBC failure under realistic service conditions.…”

Section: Introductionmentioning

confidence: 99%

Constrained sintering and cracking of air plasma sprayed thermal barrier coatings: Experimental observation and modeling

et al. 2021

View full text Add to dashboard Cite

The development of vertical cracks in air plasma sprayed (APS) thermal barrier coatings (TBCs) during thermal cycling and constrained sintering under a temperature gradient is investigated. Microstructural analysis shows that the development of the vertical cracks is associated with multiple processes, including sintering during the hold period and cleavage during cooldown. Inspired by the experimental observations, an image‐based sintering model is used to simulate the development of vertical cracks as the coating sinters while constrained by a substrate. The computational results show that microstructural imperfections can develop into vertical cracks, which then propagate toward the interface. A simple analytical model is presented for the threshold level of in‐plane stress for the onset of propagation of a vertical crack during constrained sintering. By combining the results of these different modeling approaches, the cross‐coupling of the material and geometric parameters, and how this determines the sintering response (microstructure evolution) and vertical crack formation is evaluated. In addition, the growth of vertical cracks by a cleavage mechanism during cooldown is examined and the coupling between sintering, cleavage crack growth, and TBC lifetime is explored.

show abstract

Laser Thermal Gradient Testing and Fracture Mechanics Study of a Thermal Barrier Coating

Cited by 9 publications

References 20 publications

Test-Rig Simulation on Hybrid Thermal Barrier Coating Assisted with Cooling Air System for Advanced Gas Turbine under Prolonged Exposures—A Review

Test-Rig Simulation on Hybrid Thermal Barrier Coating Assisted with Cooling Air System for Advanced Gas Turbine under Prolonged Exposures—A Review

Thermal radiative properties of zirconium oxide films in the near‐infrared wavelengths

Constrained sintering and cracking of air plasma sprayed thermal barrier coatings: Experimental observation and modeling

Contact Info

Product

Resources

About