Improvement of MCrAlY coatings by addition of rhenium

Czech, N.; Schmitz, F.; Werner, Stefan

doi:10.1016/0257-8972(94)90131-7

Cited by 111 publications

(37 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…As a consequence, Ir aluminide contains a precipitate free outer zone, a lower amount of c 0 and TCP phases in the diffusion zone. Czech et al [14] indicated that the INCO 738LC alloy with higher Re content in MCrAlY coatings showed much better oxidation resistance at 950 and 1000°C and the influence of the Re content became much more pronounced at higher temperatures, and the oxidation rate due to Re addition was lower and the depletion of the Al-rich b-phase in the coating took more time.…”

Section: Introductionmentioning

confidence: 99%

Improvement of the Oxidation Resistance of the Single-Crystal Ni-Based TMS-82+ Superalloy by Ni–Al Coatings with/without the Diffusion Barrier

Song

et al. 2010

Oxid Met

View full text Add to dashboard Cite

Oxidation behavior of the uncoated base, Ni-Al coated and Re-Cr-Ni plus Ni-Al coated single-crystal (SC) Ni-based TMS-82? superalloy is studied under cyclic air at 900°C for 200 h to assess the oxidation resistance. Regardless of the coating processing, Ni-Al coating is effective in improving the oxidation resistance due to the formation of a continuous a-Al 2 O 3 layer in the scale. For the uncoated base superalloy, the mass-gain curves are fitted by a subparabolic relationship, and complex oxide products including predominately NiO, some 123Oxid Met (2010) 74:287-303 DOI 10.1007 the cyclic exposure environment. The amount of detrimental c 0 -phase and topologically close-packed (TCP) phases in the interdiffusion zone in the coated superalloy with the diffusion barrier is greatly reduced compared with that without the diffusion barrier due to the distinct barrier effect limiting diffusion of elements between the bond-coat and the substrate.

show abstract

Section: Introductionmentioning

confidence: 99%

Improvement of the Oxidation Resistance of the Single-Crystal Ni-Based TMS-82+ Superalloy by Ni–Al Coatings with/without the Diffusion Barrier

Song

et al. 2010

Oxid Met

View full text Add to dashboard Cite

show abstract

“…It is widely recognised that the growth of the TGO during service causes progressive build-up of stress in the system, leading to the spallation of the ceramic top coat and eventually causing detrimental effects to the turbine engine components [20][21][22]. The continuous growth of the TGO due to aluminium diffusion from the MCrAlY bond coat results in subsequent  phase depletion at the oxide/bond coat interface [23][24][25][26][27][28], causing mechanical and chemical degradation of the coating. Degradation of the bond coat also occurs due to interdiffusion of element between the MCrAlY and the superalloy substrate.…”

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

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 aluminium consumed by forming the protective oxides is mainly from the Al-rich β phase which acts as the Al reservoir in the coating. The progressive loss of Al causes the β phase to deplete at the coating surface, leading to the microstructural instability of the coating [13][14][15]. The loss of β phase also occurs at the coating/substrate interface due to the interdiffusion between the coating and substrate [16][17][18][19][20][21][22][23][24][25][26][27].…”

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

View full text Add to dashboard Cite

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.

show abstract

Improvement of MCrAlY coatings by addition of rhenium

Cited by 111 publications

References 1 publication

Improvement of the Oxidation Resistance of the Single-Crystal Ni-Based TMS-82+ Superalloy by Ni–Al Coatings with/without the Diffusion Barrier

Improvement of the Oxidation Resistance of the Single-Crystal Ni-Based TMS-82+ Superalloy by Ni–Al Coatings with/without the Diffusion Barrier

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

Contact Info

Product

Resources

About