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Design of Next Generation Thermal Barrier Coatings- Experiments and Modelling
University West, Department of Engineering Science, Division of Manufacturing Processes. (PTW)ORCID iD: 0000-0002-2857-0975
University West, Department of Engineering Science, Division of Manufacturing Processes. (PTW)ORCID iD: 0000-0003-0209-1332
University West, Department of Engineering Science, Division of Production Engineering. (PTW)ORCID iD: 0000-0002-9578-4076
University West, Department of Engineering Science, Division of Production Engineering. (PTW)ORCID iD: 0000-0001-7787-5444
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2013 (English)In: Surface and Coatings Technology, ISSN 0257-8972, Vol. 220, p. 20-26Article in journal (Refereed) Published
Abstract [en]

Thermal barrier coating (TBC) systems have been used in the gas turbine industry since the 1980's. The future needs of both the air and land based turbine industry involve higher operating temperatures with longer lifetime on the component so as to increase power and efficiency of gas turbines. The aim of this study was to meet these future needs by further development of zirconia coatings. The intention was to design a coating system which could be implemented in industry within the next three years. Different morphologies of ceramic topcoat were evaluated; using dual layer systems and polymers to generate porosity. Dysprosia stabilised zirconia was also included in this study as a topcoat material along with the state-of-the-art yttria stabilised zirconia (YSZ). High purity powders were selected in this work. Microstructure was assessed with scanning electron microscope and an in-house developed image analysis routine was used to characterise porosity content. Evaluations were carried out using the laser flash technique to measure thermal conductivity. Lifetime was assessed using thermo-cyclic fatigue testing. Finite element analysis was utilised to evaluate thermal-mechanical material behaviour and to design the morphology of the coating with the help of an artificial coating morphology generator through establishment of relationships between microstructure, thermal conductivity and stiffness. It was shown that the combined empirical and numerical approach is an effective tool for developing high performance coatings. The results show that large globular pores and connected cracks inherited within the coating microstructure result in a coating with best performance. A low thermal conductivity coating with twice the lifetime compared to the industrial standard today was fabricated in this work.

Place, publisher, year, edition, pages
2013. Vol. 220, p. 20-26
Keywords [en]
Thermal barrier coatings, Microstructure, Thermal conductivity, Lifetime, Finite element modelling, Young's modulus, WIL, Work-integrated learning
Keywords [sv]
AIL
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Work Integrated Learning
Identifiers
URN: urn:nbn:se:hv:diva-4687DOI: 10.1016/j.surfcoat.2012.09.015ISI: 000317875800004Scopus ID: 2-s2.0-84875498863OAI: oai:DiVA.org:hv-4687DiVA, id: diva2:556965
Available from: 2012-09-26 Created: 2012-09-26 Last updated: 2018-07-03Bibliographically approved
In thesis
1. Design of Microstructures in Thermal Barrier Coatings: A Modelling Approach
Open this publication in new window or tab >>Design of Microstructures in Thermal Barrier Coatings: A Modelling Approach
2013 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Plasma sprayed Thermal Barrier Coating systems (TBCs) are commonly used for thermal protection of components in modern gas turbine application such as power generation, marine and aero engines. The material that is most commonly used in these applications is Yttria Stabilized Zirconia (YSZ) because of this ceramic’s favourable properties, such as low thermal conductivity, phase stability to high temperature, and good erosion resistance. The coating microstructures in YSZ coatings are highly heterogeneous, consisting of defects such as pores and cracks of different sizes which determine the coating’s final thermal and mechanical properties, and the service lives of the coatings. Determination of quantitative microstructure–property correlations is of great interest as experimental procedures are time consuming and expensive.

This objective of this thesis work was to investigate the relationships between coating microstructure and thermal-mechanical properties of TBCs, and to utilise these relationships to design an optimised microstructure to be used for next generation TBCs. Simulation technique was used to achieve this goal. Important microstructural parameters influencing the performance of TBCs were identified and coatings with the identified microstructural parameters were designed, modelled and experimentally verified. TBCs comprising of large globular pores with connected cracks inherited within the coating microstructure were shown to have significantly enhanced performance. Low thermal conductivity, low Young‘s modulus and high lifetime were exhibited by these coatings. The modelling approach described in this work can be used as a powerful tool to design new coatings as well as to achieve optimised microstructures.

Place, publisher, year, edition, pages
Göteborg: Chalmers University of Technology, 2013. p. 40
Series
Technical report / Department of Materials and Manufacturing Technology, Chalmers University of Technology, ISSN 1652-8891 ; 81
Keywords
thermal barrier coatings, microstructure, thermal conductivity, Young‘s modulus, lifetime, finite element modelling, design
National Category
Mechanical Engineering Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-5065 (URN)
Presentation
2013-03-01, F127, University West, Trollhättan, 10:00 (English)
Opponent
Supervisors
Available from: 2013-03-11 Created: 2013-01-18 Last updated: 2016-08-16Bibliographically approved
2. Design of Thermal Barrier Coatings: A modelling approach
Open this publication in new window or tab >>Design of Thermal Barrier Coatings: A modelling approach
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Atmospheric plasma sprayed (APS) thermal barrier coatings (TBCs) are commonly used for thermal protection of components in modern gas turbine application such as power generation, marine and aero engines. TBC is a duplex material system consisting of an insulating ceramic topcoat layer and an intermetallic bondcoat layer. TBC microstructures are highly heterogeneous, consisting of defects such as pores and cracks of different sizes which determine the coating's final thermal and mechanical properties, and the service lives of the coatings. Failure in APS TBCs is mainly associated with the thermo-mechanical stresses developing due to the thermally grown oxide (TGO) layer growth at the topcoat-bondcoat interface and thermal expansion mismatch during thermal cycling. The interface roughness has been shown to play a major role in the development of these induced stresses and lifetime of TBCs.The objective of this thesis work was two-fold for one purpose: to design an optimised TBC to be used for next generation gas turbines. The first objective was to investigate the relationships between coating microstructure and thermal-mechanical properties of topcoats, and to utilise these relationships to design an optimised morphology of the topcoat microstructure. The second objective was to investigate the relationships between topcoat-bondcoat interface roughness, TGO growth and lifetime of TBCs, and to utilise these relationships to design an optimal interface. Simulation technique was used to achieve these objectives. Important microstructural parameters influencing the performance of topcoats were identified and coatings with the feasible identified microstructural parameters were designed, modelled and experimentally verified. It was shown that large globular pores with connected cracks inherited within the topcoat microstructure significantly enhanced TBC performance. Real topcoat-bondcoat interface topographies were used to calculate the induced stresses and a diffusion based TGO growth model was developed to assess the lifetime. The modelling results were compared with existing theories published in previous works and experiments. It was shown that the modelling approach developed in this work could be used as a powerful tool to design new coatings and interfaces as well as to achieve high performance optimised morphologies.

Place, publisher, year, edition, pages
Trollhättan: University West, 2014. p. xvi, 85
Series
PhD Thesis: University West ; 5
Keywords
Thermal barrier coatings, Microstructure, Thermal conductivity, Young’s modulus, Interface roughness, Thermally grown oxide, Lifetime, Finite element modelling, Design
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-7181 (URN)978-91-87531-06-4 (ISBN)
Public defence
2015-01-28, 09:00 (English)
Opponent
Supervisors
Available from: 2014-12-16 Created: 2014-12-16 Last updated: 2016-08-16Bibliographically approved

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Gupta, Mohit KumarCurry, NicholasMarkocsan, NicolaieNylén, PerVaßen, Robert

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