Low Thermal Conductivity EB-PVD Thermal Barrier Coatings

Nicholls, John; Lawson, K.J.; Johnstone, Andrew; Rickerby, D.S.

doi:10.4028/www.scientific.net/msf.369-372.595

Cited by 43 publications

(28 citation statements)

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“…Scattering occurs because phonons interact with imperfections such as dislocations, vacancies, pores and grain boundaries, and the greater the density of these, the greater the scattering. The phonon mean free path (l p ) of a lattice phonon is defined by [24,25]:…”

Section: Thermal Conductivity Of Coatingsmentioning

confidence: 99%

Thermal conductivity of EB-PVD ZrO2–4mol% Y2O3 films using the laser flash method

Jang

Sakka

Yamaguchi

et al. 2011

Journal of Alloys and Compounds

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Section: Thermal Conductivity Of Coatingsmentioning

confidence: 99%

Thermal conductivity of EB-PVD ZrO2–4mol% Y2O3 films using the laser flash method

Jang

Sakka

Yamaguchi

et al. 2011

Journal of Alloys and Compounds

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“…TBC systems consist of a ceramic top coat, a metallic bond coat and a superalloy substrate [3][4][5]. Additionally, a thermally grown oxide (TGO) forms at the interface between the top coat and the bond coat during service at elevated temperature due to the fact that oxygen permeates through the ceramic top coat and oxidises the bond coat.…”

Section: Introductionmentioning

confidence: 99%

Modelling and experimental study on β-phase depletion behaviour of HVOF sprayed free-standing CoNiCrAlY coatings during oxidation

Chen

Jackson

Voisey

et al. 2016

Surface and Coatings Technology

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This paper investigates the β-phase depletion behaviour during oxidation of free-standing CoNiCrAlY (Co-31.7%Ni-20.8%Cr-8.1%Al-0.5%Y, all in wt%) bond coats prepared by high velocity oxy-fuel (HVOF) thermal spraying. The microstructure of the coatings was characterised using scanning electron microscopy with energy dispersive X-ray (EDX) analysis and electron backscatter diffraction (EBSD). It comprises a two phase structure of fcc-Ni and bcc -NiAl, with grain sizes varying largely from 0.5 to 2 µm for both phases.Isothermal oxidation tests of the free-standing coatings were carried out at 1100 C for times up to 250 h. The phase depletion behaviour at the surface was measured and was also simulated using Thermo-Calc and DICTRA software. An Al flux function derived from an oxide growth model was employed as the boundary condition in the diffusion model. The diffusion calculations were performed using the TTNi7 thermodynamic database together with the MOB2 mobility database. Reasonable agreement was achieved between the measured and the predicted element concentration and phase fraction profiles after various 2 time periods. Grain boundary diffusion is likely to be important to element diffusion in this HVOF sprayed CoNiCrAlY coating due to the sub-micron grains. Keywords IntroductionThermal barrier coatings (TBCs) are widely used to protect high temperature components in turbine engines from harsh operating environments [1,2]. TBC systems consist of a ceramic top coat, a metallic bond coat and a superalloy substrate [3][4][5]. Additionally, a thermally grown oxide (TGO) forms at the interface between the top coat and the bond coat during service at elevated temperature due to the fact that oxygen permeates through the ceramic top coat and oxidises the bond coat. The durability of the overall TBC system is largely determined by the microstructural, chemical and mechanical characteristics of the bond coat due to interdiffusion of element between the MCrAlY and the superalloy substrate. This is not considered in the present paper but has been studied by others, e.g. [29][30][31][32][33][34][35][36][37][38][39][40][41]. In these research works, the emphasis has been on substrate/bond coat interdiffusion and specific comparisons between measured and predicted β-phase depletion at the oxide/bond coat interface have not been considered. On the other hand, several analytical models concerned with the oxidation of 4 two phase systems in which the secondary phase dissolves during oxidation have been reported, e.g. [42][43][44][45][46][47][48]. In these models, the secondary phase depletion behaviour during oxidation can generally be represented by the parabolic diffusion law, Eq. (1), ~√( 1) where is the width of the second phase depletion zone and is the oxidation time.Considering the significance of β depletion on the degradation of TBCs, therefore, the aims of the work reported in this paper were to investigate specifically the kinetics of β depletion at the oxide surface in free-standing MCrAlY coatings ...

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“…The results reveal the presence of a high porosity region near the substrate (competition zone) consistent with modeling results. [11,19] The columns with preferred orientation grow beyond this point, thus showing a monotonic increase in porosity (intercolumnar spacing) toward the top surface of the coating. A sharp increase in porosity toward the surface is the region of the tip of the columns.…”

Section: Resultsmentioning

confidence: 97%

Microstructural characterization of electron beam-physical vapor deposition thermal barrier coatings through high-resolution computed microtomography

Kulkarni

Herman

DeCarlo

et al. 2004

Metall Mater Trans A

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Thermal barrier coatings (TBCs), deposited using the electron beam-physical vapor deposition (EB-PVD) process, comprise a unique architecture of porosity capable of bridging the technological gap between insulation/life extension and prime reliance. The TBC microstructures consist of columnar structure, nucleated via vapor condensation, along with a high degree of intercolumnar porosity, thus providing enhanced stress relief on thermomechanical loading and also accommodating misfit stresses resulting from CTE mismatch. In this article, we report the characterization of these coatings using high-resolution synchrotron-based X-ray computed microtomography (XMT) at 1.3-m resolution. Experiments focused on quantitative characterization/visualization of imperfections in these coatings and on the relative changes in microstructural features upon isothermal annealing. The influence of time/temperature of exposure was investigated and the results were correlated with elastic modulus.

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Low Thermal Conductivity EB-PVD Thermal Barrier Coatings

Cited by 43 publications

References 0 publications

Thermal conductivity of EB-PVD ZrO2–4mol% Y2O3 films using the laser flash method

Thermal conductivity of EB-PVD ZrO2–4mol% Y2O3 films using the laser flash method

Modelling and experimental study on β-phase depletion behaviour of HVOF sprayed free-standing CoNiCrAlY coatings during oxidation

Microstructural characterization of electron beam-physical vapor deposition thermal barrier coatings through high-resolution computed microtomography

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