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Improving the lifetime of suspension plasma sprayed thermal 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, Division of Subtractive and Additive Manufacturing. (PTW)ORCID iD: 0000-0002-9578-4076
Siemens Industrial Turbomachinery AB, Finspong, Sweden.
Linköping University, Linköping, Sweden.
2017 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 332, p. 550-559Article in journal (Refereed) Published
Abstract [en]

Development of thermal barrier coating systems (TBCs) for gas turbine applications allowing higher combustion temperatures is of high interest since it results in higher fuel efficiency and lower emissions. TBCs produced by suspension plasma spraying (SPS) have been shown to exhibit significantly lower thermal conductivity as compared to conventional systems due to their very fine porosity microstructure. However they have not been commercialised yet due to low reliability and life expectancy of the coatings. In addition to the initial topcoat microstructure and its sintering resistance, lifetime of a TBC system is highly dependent on bondcoat chemistry as it influences the growth rate of thermally grown oxide (TGO) layer. To enhance the lifetime of SPS TBCs, fundamental understanding of relationships between topcoat microstructure and its evolution with time, bondcoat chemistry, TGO growth rate, and lifetime is essential. The objective of this work was to study the effect of topcoat microstructure evolution and TGO growth rate on lifetime in SPS TBC systems. Experimental MCrAlY bondcoat powders with different aluminium activities were investigated and compared to a commercial bondcoat powder. High velocity air fuel spraying was used for bondcoat deposition while axial-SPS was used for yttria stabilized zirconia topcoat deposition. Lifetime was examined by thermal cyclic fatigue testing. Isothermal heat treatment was performed to study TGO evolution with time. The changes in microstructure of SPS coatings due to sintering under long term exposure at high temperatures were investigated. Different failure modes in SPS TBCs were also examined. The bondcoat with higher aluminium activity resulted in a significantly higher thermal cyclic lifetime of the corresponding TBC as it could have promoted protective alumina layer growth for a longer period of time. The results indicate that the significant changes in topcoat microstructure due to sintering as observed in this work could have a detrimental effect on TBC lifetime. © 2017 Elsevier B.V.

Place, publisher, year, edition, pages
Elsevier B.V. , 2017. Vol. 332, p. 550-559
Keywords [en]
Air; Alumina; Aluminum; Coatings; Combustion; Deposition; Fatigue testing; Gas emissions; Gas turbines; Growth rate; Microstructure; Plasma jets; Plasma spraying; Sintering; Sprayed coatings; Thermal conductivity; Thermal spraying; Yttria stabilized zirconia; Zirconia, Bond coats; Lifetime; Suspension plasma spraying; Thermal barrier coating (TBCs); Thermally grown oxide, Thermal barrier coatings
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
URN: urn:nbn:se:hv:diva-11885DOI: 10.1016/j.surfcoat.2017.07.078ISI: 000418968100064Scopus ID: 2-s2.0-85029643304OAI: oai:DiVA.org:hv-11885DiVA, id: diva2:1163006
Available from: 2017-12-05 Created: 2017-12-05 Last updated: 2018-01-18Bibliographically approved

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Gupta, Mohit KumarMarkocsan, Nicolaie

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