Porosity and Thermal Cycling Behavior of Plasma Sprayed and EBPVD Thermal Barrier Coatings

Agu, Ogad A.; Diwan, Ravinder; Mensah, Patrick; Silva, Monica B.; Guo, Shengmin

doi:10.1115/gt2010-22433

Cited by 3 publications

(5 citation statements)

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“…Normally a higher value is expected for samples that have gone through a high temperature sintering and densification process. For the samples tested [23], the APS-STD300 samples are found to have the lowest thermal conductivity value compared with APS-STD600 and APS-VC300, and APS-VC600. This is believed to follow phonon-phonon scattering theory.…”

Section: Thermo-physical Properties Characterization Resultsmentioning

confidence: 91%

“…[22][23]. As presented in [22] the plots of the processed VC samples that were characterized for thermal diffusivity and thermal conductivity up 1300 This has been made possible by using a boron nitride spray coating on the surface of specimen to eliminate semi transparency effects of the YSZ that impedes the laser flash measurements.…”

Section: Thermo-physical Properties Characterization Resultsmentioning

confidence: 99%

“…Table 1 comparing different processed TBC samples of varying thickness as well as processing conditions. [23]. For EBPVD specimens, NT refers to not tumbled specimen condition and T refers to tumbled condition of the disk samples prior to EBPVD coatings.…”

Section: Thermo-physical Properties Characterization Resultsmentioning

confidence: 99%

See 2 more Smart Citations

A Study of Advanced Materials for Gas Turbine Coatings at Elevated Temperatures Using Selected Microstructures and Characteristic Environments for Syngas Combustion

Diwan¹,

Mensah²,

Li³

et al. 2011

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Thermal barrier coatings (TBCs) that can be suitable for use in industrial gas turbine engines have been processed and compared with electron beam physical vapor deposition (EBPVD) microstructures for applications in advanced gas turbines that use coal-derived synthesis gas. Thermo-physical properties have been evaluated of the processed air plasma sprayed TBCs with standard APS-STD and vertically cracked APS-VC coatings samples up to 1300 o C. Porosity of these selected coatings with related microstructural effects have been analyzed in this study. Wet and dry thermal cycling studies at 1125 o C and spalling resistance thermal cycling studies to 1200 o C have also been carried out. Type I and Type II hot corrosion tests were carried out to investigate the effects of microstructure variations and additions of alumina in YSZ top coats in multi-layered TBC structures. The thermal modeling of turbine blade has also been carried out that gives the capability to predict in-service performance temperature gradients. In addition to isothermal high temperature oxidation kinetics analysis in YSZ thermal barrier coatings of NiCoCrAlY bond coats with 0.25% Hf. This can affect the failure behavior depending on the control of the thermally grown oxide (TGO) growth at the interface. The TGO growth kinetics is seen to be parabolic and the activation energies correspond to interfacial growth kinetics that is controlled by the diffusion of O 2 in Al 2 O 3 . The difference between oxidation behavior of the VC and STD structures are attributed to the effects of microstructure morphology and porosity on oxygen ingression into the zirconia and TGO layers. The isothermal oxidation resistance of the STD and VC microstructures is similar at temperatures up to 1200 o C. However, the generally thicker TGO layer thicknesses and the slightly faster oxidation rates in the VC microstructures are attributed to the increased ingression of oxygen through the grain boundaries of the vertically cracked microstructures. The plasma sprayed TBC microstructure (VC and STD) with NiCoCrAlY-Hf bond coat are stable up to 1100 o C. However, as with other TBC structures, a considerable amount of interdiffusion was observed in the different layers, although the TBC growth was self-limiting and parabolic. The addition of Hf to the VC microstructure appears to have some potential for the future development of robust TBCs with improved isothermal and service temperatures in advanced gas turbines.

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Section: Thermo-physical Properties Characterization Resultsmentioning

confidence: 91%

Section: Thermo-physical Properties Characterization Resultsmentioning

confidence: 99%

See 1 more Smart Citation

A Study of Advanced Materials for Gas Turbine Coatings at Elevated Temperatures Using Selected Microstructures and Characteristic Environments for Syngas Combustion

Diwan¹,

Mensah²,

Li³

et al. 2011

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“…Methods such as magnetic particle testing, dye penetrant and The non-wetting liquid (mercury) requires pressure application to get into the pores and voids. The method can be used to measure pore diameters of up to 0.0070 µm [69]. Total porosity is computed by considering the total volume of mercury intruded into the voids in the samples and the bulk volume of the sample.…”

Section: Nondestructive Testing (Ndt)mentioning

confidence: 99%

Porosity and Its Significance in Plasma-Sprayed Coatings

et al. 2019

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Porosity in plasma-sprayed coatings is vital for most engineering applications. Porosity has its merits and demerits depending on the functionality of the coating and the immediate working environment. Consequently, the formation mechanisms and development of porosity have been extensively explored to find out modes of controlling porosity in plasma-sprayed coatings. In this work, a comprehensive review of porosity on plasma-sprayed coatings is established. The formation and development of porosity on plasma-sprayed coatings are governed by set spraying parameters. Optimized set spraying parameters have been used to achieve the most favorable coatings with minimum defects. Even with the optimized set spraying parameters, defects like porosity still occur. Here, we discuss other ways that can be used to control porosity in plasma-sprayed coating with emphasis to atmospheric plasma-sprayed chromium oxide coatings. Techniques like multilayer coatings, nanostructured coatings, doping with rare earth elements, laser surface re-melting and a combination of the above methods have been suggested in adjusting porosity. The influences of porosity on microstructure, properties of plasma-sprayed coatings and the measurement methods of porosity have also been reviewed.

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“…The method can be used to measure pore diameters of up to 0.0070µ m [55]. Total porosity is computed by considering the total volume of mercury intruded into the voids in the samples and the bulk volume of the sample.…”

Section: Mercury Intrusion Porosimetrymentioning

confidence: 99%

Porosity and Its Significance in Plasma Sprayed Coating: A Review

Odhiambo¹,

Li²,

Zhao³

et al. 2019

Preprint

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Porosity in plasma sprayed coatings is vital for most engineering applications. It is either advantageous or disadvantageous depending on the functionality of the coating and the immediate working environment. Consequently, the formation mechanisms and development of porosity has been extensively explored to find out modes of controlling porosity in plasma sprayed coatings. In this work, a comprehensive review of porosity on plasma sprayed coatings is established. The formation and development of porosity on plasma sprayed coatings are governed by set spraying parameters. Optimized set spraying parameters have been used to achieve the most favorable coatings with minimum defects. Even with the optimized set spraying parameters, defects like porosity still occur. Here, we discuss other ways that can be used to control porosity in plasma sprayed coating with emphasis to atmospheric plasma sprayed chromium oxide coatings. Techniques like multi-layer coatings, nano-structured coatings, doping with rare earth elements, laser surface re-melting and a combination of the above methods have been suggested in adjusting porosity. The influences of porosity on properties of plasma sprayed coatings and the measurement methods of porosity have also been reviewed.

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Porosity and Thermal Cycling Behavior of Plasma Sprayed and EBPVD Thermal Barrier Coatings

Cited by 3 publications

References 0 publications

A Study of Advanced Materials for Gas Turbine Coatings at Elevated Temperatures Using Selected Microstructures and Characteristic Environments for Syngas Combustion

A Study of Advanced Materials for Gas Turbine Coatings at Elevated Temperatures Using Selected Microstructures and Characteristic Environments for Syngas Combustion

Porosity and Its Significance in Plasma-Sprayed Coatings

Porosity and Its Significance in Plasma Sprayed Coating: A Review

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