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Influence of Topcoat-Bondcoat Interface Roughness on Stresses and Lifetime inThermal Barrier Coatings
University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. (PTW)ORCID iD: 0000-0002-2857-0975
University West, Department of Engineering Science. (PTW)
University West, Department of Engineering Science, Division of Production Engineering. (PTW)ORCID iD: 0000-0001-7787-5444
2014 (English)In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 23, no 1-2, p. 170-181Article in journal (Refereed) Published
Abstract [en]

Failure in Atmospheric Plasma Sprayed (APS) Thermal Barrier Coatings (TBCs) is associated with the thermo-mechanical stresses developing due to the Thermally Grown Oxide (TGO) layer growth 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. Modeling has been shown as an effective tool to understand the effect of interface roughness on induced stresses. In previous work done by our research group, it was observed that APS bondcoats performed better than the bondcoats sprayed with High Velocity Oxy-Fuel (HVOF) process which is contrary to the present literature data. The objective of this work was to understand this observed difference in lifetime with the help of finite element modeling by using real surface topographies. Different TGO layer thicknesses were evaluated. The modeling results were also compared with existing theories established on simplified sinusoidal profiles published in earlier works. It was shown that modeling can be used as an effective tool to understand the stress behavior in TBCs with different roughness profiles.

Place, publisher, year, edition, pages
2014. Vol. 23, no 1-2, p. 170-181
Keywords [en]
finite element modeling, interface roughness, lifetime, stress state, thermal barrier coatings
National Category
Mechanical Engineering Other Materials Engineering
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
URN: urn:nbn:se:hv:diva-5775DOI: 10.1007/s11666-013-0022-9ISI: 000329106200022Scopus ID: 2-s2.0-84891830219OAI: oai:DiVA.org:hv-5775DiVA, id: diva2:676721
Conference
2013 International Thermal Spray Conference in Busan, South Korea, held May 13-15, 2013.
Available from: 2013-12-06 Created: 2013-12-06 Last updated: 2018-07-03Bibliographically approved
In thesis
1. 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 KumarNylén, Per

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