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

SURFACE & COATINGS TECHNOLOGY

卷:313

Article

Chen, H.¹  McCartney, D. G.² 

[1] Univ Nottingham Ningbo China, Fac Sci & Engn, Dept Mech Mat & Mfg Engn, Ningbo 315100, Peoples R China

[2] Univ Nottingham, Fac Engn, Adv Mat Res Grp, Univ Pk, Nottingham NG7 2RD, England

关键词: HVOF spraying;    MCrAIY coating;    beta depletion;    Diffusion;    Oxidation;   

DOI  :  10.1016/j.surfcoat.2017.01.075

来源: Elsevier

【 摘 要 】

In this paper, beta-phase depletion behaviour of free-standing high velocity oxy-fuel (HVOF) thermally sprayed CoNiCrAIY coatings was studied. Microstructural analysis showed a two-phase microstructure of gamma-Ni matrix and beta-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 pm or even less for both phases. The beta-phase depletion behaviour was investigated during isothermal oxidation and was also modelled through diffusion calculations. A previously developed beta-phase depletion model was utilised to study the evolution of beta-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 hat 1100 degrees C, but discrepancies were noted at longer oxidation times. Further improvements on closely modelling the oxidation kinetics and the effective diffusion behaviour are needed to minimise the discrepancies at longer oxidation times. (C) 2017 Elsevier B.V. All rights reserved.

【 授权许可】

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