Modelling the microstructural evolution and degradation of M-Cr-Al-Y coatings during high temperature oxidation

Lee, E.Y.; Chartier, D.; Biederman, R.R.; Sisson, Richard D.

doi:10.1016/0257-8972(87)90095-8

Cited by 66 publications

(31 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Taken the diffusion data from Karunaratne et al [31], D eff is found to be 1.19×10 -14 m 2 /s. The magnitude falls into the right range of the previously reported work [29,42]. It has to be emphasised that the D eff used here may not be the exact effective diffusion coefficient in this…”

Section: β-Phase Coarsening Kineticssupporting

confidence: 55%

See 1 more Smart Citation

An analytical approach to the β-phase coarsening behaviour in a thermally sprayed CoNiCrAlY bond coat alloy

Chen

McCartney

2017

Journal of Alloys and Compounds

View full text Add to dashboard Cite

This paper investigates the β-phase coarsening behaviour during isothermal heat treatment of free-standing CoNiCrAlY (Co-31.7%Ni-20.8%Cr-8.1%Al-0.5%Y, all in wt%) coatings 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 γ-Ni matrix and bcc β-NiAl precipitates. The volume fraction of the γ-Ni and the β-NiAl phases were measured to be around 70% and 30% respectively, with grain sizes varying largely from 0.5 to 2 µm for both phases. Isothermal heat treatments of the freestanding coatings were carried out at 1100 C for times up to 250 h. The β-phase coarsening behaviour during isothermal heat treatments was analysed by quantitative metallography. It is shown that the coarsening behaviour of β phase in the CoNiCrAlY alloy followed the classical Lifshitz-Slyozov-Wagner (LSW) theory of Ostwald ripening. By incorporating a dimensionless factor which correlates with volume fraction of the β phase, a modified LSW model coupled with formulaic interfacial energy and effective diffusion coefficient of the 2 CoNiCrAlY alloy was utilised to interpret the coarsening behaviour of the β phase. The coarsening rate coefficient obtained from the modified LSW model shows good agreement with the corresponding experimental result.

show abstract

Section: β-Phase Coarsening Kineticssupporting

confidence: 55%

“…[28][29][30][31][32][33][34][35][36][37][38]. In these research works, the emphasis has been on oxide growth, phase transformation and element diffusion, but specific concerns on the β-phase coarsening behaviour in the MCrAlY coating have not been addressed.…”

Section: Introductionmentioning

confidence: 99%

An analytical approach to the β-phase coarsening behaviour in a thermally sprayed CoNiCrAlY bond coat alloy

Chen

McCartney

2017

Journal of Alloys and Compounds

View full text Add to dashboard Cite

show abstract

“…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.…”

mentioning

confidence: 98%

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

View full text Add to dashboard Cite

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 ...

show abstract

“…The removal of Al from the coating results in the dissolution of the β-phase, thus giving rise to β-depleted zones at the coating surface, due to oxidation, and at the coating-substrate interface, due to interdiffusion [6,15,16]. When the β-phase is completely depleted, or when the Al concentration reaches a critically low value, the coating can no longer work as an Al reservoir and less-protective oxides forms [2,6,13,[15][16][17]; the depletion of aluminum thus marks the end of the useful life of the coating [3].…”

Section: Introductionmentioning

confidence: 99%

“…As oxidation resistance is achieved by the formation of alumina, the useful life of the coating is often determined by the Al depletion that occurs through oxidation and interdiffusion [3,5,6,[15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Modeling of microstructural evolution and lifetime prediction of MCrAlY coatings on nickel based superalloys during high temperature oxidation

Yuan

Eriksson

Peng

et al. 2013

Surface and Coatings Technology

View full text Add to dashboard Cite

MCrAlY coatings are deposited onto superalloys to provide oxidation and corrosion protection at high temperature by the formation of a thermally grown oxide scale. In this project, the oxidation behaviour of a HVOF CoNiCrAlYSi coating on IN792 was studied for both isothermal oxidation (900, 1000 and 1100 °C) and thermal cycling (100-1100 °C). The microstructural evolution of the CoNiCrAlYSi coatings after oxidation was investigated. It was found that the Al-rich β phase is gradually consumed due to two effects: surface oxidation and coating-substrate interdiffusion. Some voids and oxides along the coating-substrate interface, or inside the coating, were considered to play a role in blocking the diffusion of alloying elements. Based on the microstructural observation, an oxidation-diffusion model, considering both surface oxidation and coating-substrate interdiffusion, was developed by using Matlab and DICTRA software to predict the useful life of MCrAlY coatings.A new concept of diffusion blocking is also introduced into the model to give more accurate description on the microstructural evolution. The results from modeling and the experimentally established composition profiles showed good agreement.

show abstract

Modelling the microstructural evolution and degradation of M-Cr-Al-Y coatings during high temperature oxidation

Cited by 66 publications

References 5 publications

An analytical approach to the β-phase coarsening behaviour in a thermally sprayed CoNiCrAlY bond coat alloy

An analytical approach to the β-phase coarsening behaviour in a thermally sprayed CoNiCrAlY bond coat alloy

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

Modeling of microstructural evolution and lifetime prediction of MCrAlY coatings on nickel based superalloys during high temperature oxidation

Contact Info

Product

Resources

About