High-temperature Oxidation Behavior and Surface Roughness Evolution of VPS NiCrAlY Coating

Seo, Do Won; Ogawa, Kōichi; Shoji, Tetsuo; Murata, Shozo

doi:10.1007/s11666-007-9150-4

Cited by 21 publications

(11 citation statements)

References 17 publications

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“…This agrees with other work reported in the literature [12,19,58]. It has also been reported that surface roughness can affect the yttrium distribution by forming yttrium aluminides in concave regions of the coating [59], but this has not been observed in this study.…”

Section: Surface Roughnesssupporting

confidence: 92%

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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Section: Surface Roughnesssupporting

confidence: 92%

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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“…low pressure plasma spraying (LPPS), vacuum plasma spraying (VPS) and, more recently, high velocity oxy-fuel (HVOF) thermal spraying [28][29][30][31][32][33][34][35][36][37][38][39][40]. It is generally recognised that the rate of Al loss and the β-phase depletion behaviour is closely related to the oxide growth kinetics at the oxide/coating interface.…”

Section: Introductionmentioning

confidence: 99%

Some aspects on modelling of the β-phase depletion behaviour under different oxide growth kinetics in HVOF CoNiCrAlY coatings

Chen

McCartney

2017

Surface and Coatings Technology

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In this paper, β-phase depletion behaviour of free-standing high velocity oxy-fuel (HVOF) thermally sprayed CoNiCrAlY coatings was studied. Microstructural analysis showed a twophase microstructure of γ-Ni matrix and β-NiAl secondary phase after heat treatment. Fine grains were found around the sprayed particle boundaries and coarse grains were retained as the original particle structure, with grain sizes varying from 2 to 0.5 µm or even less for both phases. The β-phase depletion behaviour was investigated during isothermal oxidation and was also modelled through diffusion calculations. A previously developed β-phase depletion model was utilised to study the evolution of β-phase depletion under different oxide growth kinetics. Three oxide growth models were tried: 1) Meier model, 2) thermogravimetric analysis (TGA) model, and 3) experimentally fitted oxide growth model. The oxide growth kinetics were converted to Al flux functions which were used as the boundary conditions in the DICTRA modelling. It is shown that the results obtained from the three models exhibit good agreements between the measured and predicted results for times up to 100 h at 1100 C, but discrepancies were noted at longer oxidation times. Further improvements on closely 2 modelling the oxidation kinetics and the effective diffusion behaviour are needed to minimise the discrepancies at longer oxidation times.

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“…NiCrAlY, CoNiCrAlY and NiCoCrAlY coatings have been obtained by various techniques such as vacuum plasma spray (VPS) [15][16][17][18][19], electron beam physical vapor deposition (EB-PVD) [20], air plasma spray (APS) [21][22][23], high frequency pulse detonation (HFPD) [24] and high velocity oxygen fuel (HVOF) [10,12,16,19,21,[25][26][27][28][29][30][31]. In recent years, HVOF sprayed coatings has been particularly interesting because they possess high density, strong substrate adhesion and are able to maintain nano-scale structure after spraying [32].…”

Section: Introductionmentioning

confidence: 99%

Thermal stability and oxidation behavior of nanostructured NiCoCrAlY coatings

Mercier

Gauntt

Brochu

2011

Surface and Coatings Technology

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High-temperature Oxidation Behavior and Surface Roughness Evolution of VPS NiCrAlY Coating

Cited by 21 publications

References 17 publications

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

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

Some aspects on modelling of the β-phase depletion behaviour under different oxide growth kinetics in HVOF CoNiCrAlY coatings

Thermal stability and oxidation behavior of nanostructured NiCoCrAlY coatings

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