Achieving self-enhanced thermal barrier performance through a novel hybrid-layered coating design

Thermal barrier coatings (TBCs) have become an indispensable technology as the temperature of turbine inlet gas has increased. TBCs reduce the temperature of the base metal, but a reduction of internal pores by sintering occurs when using TBCs, and so the thermal barrier performance of TBCs is deteriorated. This in turn increases the temperature of the base metal and could shorten its lifespan. The authors have already clarified by laboratory acceleration tests that the deterioration of the thermal barrier performance of TBCs is caused by a decrease in the noncontact area that exists inside TBCs. This noncontact area is a slit space that exists between thin layers and is formed when TBCs are coated. This paper examines the relations between the decrease of the noncontact area and the exposure conditions, by measuring the thermal conductivity and the porosity of TBCs exposed to the temperatures that exist in an actual gas turbine, and derives the correlation with exposure conditions. As a result, very high correlations were found between the thermal conductivity and exposure conditions of TBCs, and between the porosity and exposure conditions. A very high correlation was also found between the thermal conductivity and porosity of TBCs. In addition, techniques for predicting TBC operating temperature were examined by using these three correlations. The correlation of diameter and exposure conditions of the gamma prime phase, which exists in nickel base super alloys, is used as a general method for predicting the temperature of parts in hot gas paths. This paper proposes two kinds of operating temperature prediction methods, which are similar to this general method. The first predicts the operating temperature from thermal conductivity measurements of TBCs before and after use, and the second predicts the operating temperature from thermal conductivity measurements of TBCs after use and porosity measurements before use. The TBC operating temperatures of a combustor that had been used for 12,000 hours with an actual E-class gas turbine were predicted by these two methods. The advantage of these methods is that the temperature of all parts with TBC can be predicted.

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Development of Ceramic/Metal Gradient Thermal Barrier Coating Design Software

Materials Science Forum ◽

10.4028/www.scientific.net/msf.423-425.763 ◽

2003 ◽

Vol 423-425 ◽

pp. 763-768 ◽

Cited By ~ 2

Author(s):

Jin Sheng Xiao ◽

Chun Zhi Hu ◽

Dong Zhou Cui ◽

Yun Hua Guo

Keyword(s):

Thermal Barrier Coating ◽

Thermal Barrier ◽

Barrier Coating ◽

Design Software ◽

Coating Design

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High Temperature Radiation Heat Transfer Performance of Thermal Barrier Coatings With Multiple Layered Structures

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.2967495 ◽

2008 ◽

Vol 131 (1) ◽

Cited By ~ 6

Author(s):

Xiao Huang

Keyword(s):

Heat Transfer ◽

Thermal Radiation ◽

Thermal Barrier Coatings ◽

Wavelength Range ◽

Coating Thickness ◽

Single Layer ◽

Layered Structures ◽

Thermal Barrier ◽

Barrier Coatings ◽

Layered Coating

Meeting the demands for ever increasing operating temperatures in gas turbines requires concurrent development in cooling technologies, new generations of superalloys, and thermal barrier coatings (TBCs) with increased insulation capability. In the case of the latter, considerable research continues to focus on new coating material compositions, the alloying/doping of existing yttria stabilized zirconia ceramics, and the development of improved coating microstructures. The advent of the electron beam physical vapor deposition coating process has made it possible to consider the creation of multiple layered coating structures to meet specific performance requirements. In this paper, the advantages of layered structures are first reviewed in terms of their functions in impeding thermal conduction (via phonons) and thermal radiation (via photons). Subsequently, the design and performance of new multiple layered coating structures based on multiple layered stacks will be detailed. Designed with the primary objective to reduce thermal radiation transport through TBC systems, the multiple layered structures consist of several highly reflective multiple layered stacks, with each stack used to reflect a targeted radiation wavelength range. Two ceramic materials with alternating high and low refractive indices are used in the stacks to provide multiple-beam interference. A broadband reflection of the required wavelength range is obtained using a sufficient number of stacks. In order to achieve an 80% reflectance to thermal radiation in the wavelength range 0.3–5.3μm, 12 stacks, each containing 12 layers, are needed, resulting in a total thickness of 44.9μm. Using a one dimensional heat transfer model, the steady state heat transfer through the multiple layered TBC system is computed. Various coating configurations combining multiple layered stacks along with a single layer are evaluated in terms of the temperature profile in the TBC system. When compared with a base line single layered coating structure of the same thickness, it is estimated that the temperature on the metal surface can be reduced by as much as 90°C due to the use of multiple layered coating configurations. This reduction in metal surface temperature, however, diminishes with increasing the scattering coefficient of the coating and the total coating thickness. It is also apparent that using a multiple layered structure throughout the coating thickness may not offer the best thermal insulation; rather, placing multiple layered stacks on top of a single layer can provide a more efficient approach to reducing the heat transport of the TBC system.

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Erosion Behavior of PS-PVD Thermal Barrier Coatings and the Effect of Composite Coating (PS-PVD + APS) Thickness

Materials Science Forum ◽

10.4028/www.scientific.net/msf.993.1095 ◽

2020 ◽

Vol 993 ◽

pp. 1095-1103

Author(s):

Wen Long Chen ◽

Hong Jian Wu ◽

Min Liu ◽

Xiao Ling Xiao

Keyword(s):

Thermal Barrier Coatings ◽

Erosion Resistance ◽

Failure Behavior ◽

Thermal Barrier ◽

Dense Layer ◽

Particle Erosion ◽

Barrier Coatings ◽

Erosion Behavior ◽

Layered Coating ◽

Resistance Performance

In this work, feather-column 7YSZ thermal barrier coatings (TBCs) were prepared by plasma spray-physical vapor deposition (PS-PVD). The anti-particle erosion test was carried out at room temperature to study the erosion behavior and failure mechanism of PS-PVD TBCs. The results showed that the particle erosion process of the PS-PVD TBCs experienced three stages of high-rate, medium-rate and slow-rate erosion. In order to improve the particle erosion resistance of the PS-PVD TBCs, different thicknesses of dense-layered coatings were prepared on the surface of the PS-PVD TBCs by air plasma spraying (APS). The effect of dense-layered thickness on the erosion behaviour of PS-PVD TBCs was discussed. Experimental results showed that, as the thickness of the dense-layered increased, the erosion resistance of the PS-PVD TBCs enhanced. When the thickness of the dense-layered coating was 5μm, it was not obvious upon the influence on the erosion failure behavior of the PS-PVD TBCs. In the case of a 10μm dense-layered coating, the erosion resistance performance of the PS-PVD TBCs improved by about 30%. While the erosion resistance performance of the PS-PVD TBCs increased almost 4 times when the thickness of the dense layer reached 20μm.

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Partial Transparency of Advanced Compression Ignition Combustion Chamber Deposits, Its Impact on Combustion Chamber Wall Temperatures and Application to Thermal Barrier Coating Design

SAE International Journal of Engines ◽

10.4271/03-11-02-0012 ◽

2018 ◽

Vol 11 (2) ◽

pp. 179-194 ◽

Cited By ~ 1

Author(s):

Mark Hoffman ◽

Ryan O’Donnell ◽

Zoran Filipi

Keyword(s):

Combustion Chamber ◽

Thermal Barrier Coating ◽

Chamber Wall ◽

Thermal Barrier ◽

Compression Ignition ◽

Barrier Coating ◽

Combustion Chamber Deposits ◽

Coating Design ◽

Compression Ignition Combustion

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High Temperature Radiation Heat Transfer Performance of Thermal Barrier Coatings With Multiple Layered Structures

Volume 1: Aircraft Engine; Ceramics; Coal, Biomass and Alternative Fuels; Manufacturing, Materials and Metallurgy; Microturbines and Small Turbomachinery ◽

10.1115/gt2008-50047 ◽

2008 ◽

Author(s):

Xiao Huang

Keyword(s):

Heat Transfer ◽

Thermal Radiation ◽

Thermal Barrier Coatings ◽

Wavelength Range ◽

Coating Thickness ◽

Single Layer ◽

Layered Structures ◽

Thermal Barrier ◽

Barrier Coatings ◽

Layered Coating

Meeting the demands for ever increasing operating temperatures in gas turbines requires concurrent development in cooling technologies, new generations of superalloys, and thermal barrier coatings (TBCs) with increased insulation capability. In the case of the latter, considerable research continues to focus on new coating material compositions, alloying/doping existing yttria stabilized zirconia ceramics, and the development of improved coating microstructures. The advent of the EB-PVD coating process has made it possible to consider the creation of multiple layered coating structures to meet specific performance requirements. In this paper, the advantages of layered structures are first reviewed in terms of their functions in impeding thermal conduction (via phonons) and thermal radiation (via photons). Subsequently, the design and performance of new multiple layered coating structures based on multiple layered stacks will be detailed. Designed with the primary objective to reduce thermal radiation transport through TBC systems, the multiple layered structures consist of several highly reflective multiple layered stacks, with each stack used to reflect a targeted radiation wavelength range. Two ceramic materials with alternating high and low refractive indices are used in the stacks to provide multiple-beam interference. A broadband reflection of the required wavelength range is obtained using a sufficient number of stacks. In order to achieve 80% reflectance to thermal radiation in the wavelength range of 0.3 ∼ 5.3 μm, 12 stacks, each containing 12 layers, are needed, resulting in a total thickness of 44.9 μm. Using a one dimensional heat transfer model, steady state heat transfer through the multiple layered TBC system is computed. Various coating configurations combining multiple layered stacks along with a single layer are evaluated in terms of the temperature profile in the TBC system. When compared to a baseline single layered coating structure of the same thickness, it is estimated that the temperature on the metal surface can be reduced by as much as 90°C due to the use of multiple layered coating configurations. This reduction in metal surface temperature, however, diminishes with increasing scattering coefficient of the coating and total coating thickness. It is also apparent that using a multiple layered structure throughout the coating thickness may not offer the best thermal insulation; rather, placing multiple layered stacks on top of a single layer can provide a more efficient approach to reduce the heat transport of the TBC system.

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