Sun, J.G.; Kulkarni, A.; Fry, A.T. (2024) Pulsed thermal imaging for non-destructive evaluation of hot gas path coatings in gas turbines. Materials at High Temperatures, 41 (4). pp. 557-571. ISSN 0960-3409

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Abstract

To address global research in energy technologies, a UK–US collaboration was setup to look at implications in the use of alternative gas turbine liquid/gaseous fuels and first-generation IGCC-derived syngas. The development of predictive models for deposition, corrosion and component living in gas turbines operating on such novel fuel gases is now being developed. Linked to this, the non-destructive inspection of hot gas path components needs to be refined and the life prediction models utilising thermal barrier coatings need to be validated to enable the on-going assessment of the remnant lives of components during their use. Thermal barrier coatings (TBCs) have been critical to the operation of gas turbines in aircraft and land-based applications. As the engine demands increase with respect to operational temperature and efficiency, so has the requirement for TBCs, both from the perspective of their performance (thermal conductivity, durability) as well as their reliability. Because TBCs play critical role in protecting the underlying super alloy, their failure (spallation) cause accelerated component damage leading to unplanned outage. Therefore, it is important to inspect and monitor the TBC condition to assure its quality and reliability. Non-destructive evaluation (NDE) methods would allow for direct determination of TBC thermal conductivity on coated components and, therefore, they can be used to inspect the quality of as processed components and monitor TBC degradation during service. This paper presents a new method, the pulsed thermal imaging–multilayer analysis (PTI–MLA) method, which can measure the coating thermal conductivity and heat capacity distributions for coatings on different substrates and thickness. NDE methods were also evaluated based on preliminary experimental results for TBC samples that were thermal cycled to various lifetimes to monitor TBC degradation and predict TBC life. Initial insight into the TBC response with painted and unpainted surfaces is also discussed to demonstrate next steps.

Item Type:	Article
Keywords:	Non-destructive testing, thermal barrier coatings, flash thermography, thermal conductivity, life prediction
Subjects:	Advanced Materials > Surface Engineering
Identification number/DOI:	10.1080/09603409.2020.1824853
Last Modified:	26 Feb 2025 10:48
URI:	http://eprintspublications.npl.co.uk/id/eprint/9017

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