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Some aspects of elemental behaviour in HVOF MCrAlY coatings in high-temperature oxidation
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
Siemens Industrial Turbomachinery AB, Finspång, Sweden.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
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2015 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 261, 86-101 p.Article in journal (Refereed) Published
Abstract [en]

MCrAlY coatings are widely used to protect superalloys against oxidation and corrosion at high temperature in gas turbine engines. To design a durable MCrAlY coating, the elemental behaviour in coating-superalloy couples needs to be better understood. After oxidation tests in temperature range between 900 °C to 1100 °C, the microstructural development in the samples were analysed. The investigation was mainly focused on the microstructures at the coating surface or in areas near the coating-superalloy interface. Some interdiffusion simulations were also done to model the diffusion behaviour of alloying elements in different coatingsuperalloy couples. The results showed that both oxidation at the coatings’ surfaces and the elements’ diffusion inside of the materials were temperature- and chemical-composition dependent. The behaviour of some minor elements like Y, Hf, Ru and Ir in the oxidation processes was particularly studied by tracking their position and composition in the materials.

Place, publisher, year, edition, pages
2015. Vol. 261, 86-101 p.
Keyword [en]
MCrAlY; oxidation; interdiffusion; elemental behaviour
National Category
Materials Engineering
URN: urn:nbn:se:liu:diva-111116DOI: 10.1016/j.surfcoat.2014.11.053ISI: 000348255500012OAI: diva2:753477

On the day of the defence date the status of this article was Manuscript.

Available from: 2014-10-08 Created: 2014-10-08 Last updated: 2015-04-13Bibliographically approved
In thesis
1. Oxidation and Corrosion of New MCrAlX Coatings: Modelling and Experiments
Open this publication in new window or tab >>Oxidation and Corrosion of New MCrAlX Coatings: Modelling and Experiments
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

MCrAlY coatings (“M” for Ni and/or Co) are widely used for the protection of superalloy components operated at high temperatures such as in the hot sections of gas turbines. The exposure to high temperature can cause coating degradation due to oxidation or hot corrosion at the coating surface. Microstructures in the coating and the coating life are affected also by the diffusion of alloying elements through the coating-superalloy interface. This PhD project, by applying thermodynamic modelling and experimental tests, investigates the oxidation and hot corrosion behavior of new MCrAlX coatings, in which X, referring to minor elements, is used to highlight the functions of such elements.

In order to understand and predict the coating degradation progress during thermal exposure, an oxidation-diffusion model has been established for MCrAlX coating-superalloy systems, which integrates the oxidation of aluminum at coating surface, diffusion of alloying elements, and the diffusion-blocking effect in the materials. The predicted chemical composition profile and microstructure agreed well with experimental results in a CoNiCrAlYSiTa-Inconel 792 system. The model was further applied in several coating-superalloy systems to study the influence of coating composition, superalloy composition and temperature on the evolution of microstructure in the coating and the coating life. The results have demonstrated the potential of the model in designing new durable MCrAlX coatings. In addition to the applications in coating-superalloy systems, the model was also adapted for studying the microstructural development in a superalloy in which internal oxidation and nitridation occurred in an oxidation process.

The oxidation behavior of some HVOF MCrAlX coatings was studied by thermal exposure at different temperatures (900, 1000, 1100 °C). Different spinels formed above the alumina scale, depending on the oxidation temperature. The minor alloying elements, Ru and Ir, had no direct influence on the oxidation behavior but may affect the phase stability in the coating.

MCrAlX coatings were also tested in 48-hour cycles at 900 °C in different hot corrosion environments containing sulphates and/or SO2. The results showed that the coating performance was dependent on coating quality, concentration of Al and Cr in the coating, and the hot corrosion condition. It was also found that the addition of SO2 in the environment may not necessarily be bad for hot corrosion resistance of some MCrAlY coatings.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. 46 p.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1619
National Category
Materials Engineering Mechanical Engineering
urn:nbn:se:liu:diva-111119 (URN)10.3384/diss.diva-111119 (DOI)978-91-7519-247-5 (print) (ISBN)
Public defence
2014-10-30, ACAS, Hus A, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
ELFORSK, AGORA MATERIA, Strategic Faculty Grant AFM
Available from: 2014-10-08 Created: 2014-10-08 Last updated: 2015-09-17Bibliographically approved

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