Poster Année : 2024

Study of Thermal Barrier Coatings in Water Vapor Environment using the LASDAM methodology (LAser Shock for DAmage Monitoring)

Étude des revêtements de barrière thermique dans un environnement de vapeur d'eau à l'aide de la méthodologie LASDAM (LAser Shock for DAmage Monitoring)

Eliott Degouilles
Vincent Guipont
Vincent Maurel
Basile Marchand

Résumé

Context of the TBC4H2 project In order to reduce the carbon impact of gas turbines, dihydrogen (H2) can be considered as a fuel. However, since the combustion of H2 introduces an intense flow of water vapor (temperature and pressure), the durability of thermal barrier coatings (TBC) of aero engine components in a very high temperature water vapor environment (T≥1200 °C) needs to be analysed for varying processes and properties of TBCs. This study aims to characterise the behaviour of TBC systems exposed to such conditions by the introduction of LASER-assisted characterisation techniques that are relevant to assess interfacial adhesion of TBCs from as-processed materials to in-service conditions. It is part of the M-ERA.NET TBC4H2 project: “Thermal Barrier Coatings for greener heat-to-power applications: understanding limits of operation under hydrogen combustion and sustainable outlook”. Purpose of the study It is known that damage mechanisms and coating’s spallation in TBC systems are largely driven by oxide (TGO) growth combined to cyclic thermo-mechanical loading. Thus, water vapour environments and high temperatures (T≥1200 °C) are expected to reduce TBCs lifetime considerably by modifying the oxidation kinetics, oxide morphology and reducing the interface strength during service life. Therefore, the goal of this work is to implement an original methodology involving laser shocks applied to ceramic coatings to test adhesion for different ageing conditions and also to prepare calibrated damage for further monitoring of the crack propagation in case of state-of-the art and latest generation TBC systems. Such systems involve YSZ single layer or double-layer YSZ/GZ top-coat by EB-PVD or SPS and various bond coats (NiCoCrAlY, Pt-aluminide and Pt-ɣ/ɣ’) in order to evaluate their oxidation behaviour under water vapour conditions [1] [2]. LAser Shock Adhesion Test (LASAT) applied to ceramic coatings like TBCs. The LASAT is a contactless technique that can be applied to evaluate the interfacial adherence of ceramic layer on metallic substrate. The technique uses laser-matter interaction by a nanoseconds laser pulse to produce a shockwave which travels though the couple substrate/coatings to be tested. From spatial-temporal distribution of the shockwave, it is possible to enable a tensile stress at the interface. This tensile stress is generated by the reflection of the principal wave at the rear free surface and the crossing with the incident release wave. If high enough, this tensile stress can debond the coating or even induce its local spallation for the highest laser energies. For a given coating system and a laser pulse duration (in ns) and a selected focalization, a LASAT threshold is determined by increasing the laser power density (in GW.cm-2) up to the debonding threshold. By increasing the laser energy beyond that threshold, the size of the debonded area is steadily increasing allowing to plot the so-called “LASAT curve”. In the case of ceramic coatings, the debonding can be easily determined and further measured by optical imaging or IR imaging. Such technique is developed to assess the adhesion of ceramic top-coat across different stages of a TBC lifetime. In this manner, it is possible to have a direct qualitative comparison of the ceramic adhesion in its as-deposited state and after exposure to various durations of thermal cycling by analysing the relative position of the “LASAT curve”. LASDAM of TBCs involving thermal cycling and high temperature corrosion The LASDAM (LAser Shock for DAmage Monitoring) methodology consists of introducing a defect calibrated in size and position into the ceramic/metal system by means of a laser shock. Knowing this defect, it is possible to monitor in situ the evolution of the interfacial damage for TBCs subjected to thermomechanical stresses. Optical imaging and infrared thermography imaging (IRT) enable revealing and measuring defects in a non-destructive manner, then to monitor their evolution with thermal cycling. As a complement, profilometry measurements provide information about the blister height which makes it possible to highlight buckling caused by residual stress release in the ceramic layer. From such LASDAM methodology, it is possible to discriminate the crack propagation from the buckling of the ceramic top-coat for further FE calculations of the blister’s behaviour [3]. References [1] K. A. Unocic and B. A. Pint, “Effect of water vapor on thermally grown alumina scales on bond coatings,” Surf. Coat. Technol., vol. 215, pp. 30–38, 2013, doi: 10.1016/j.surfcoat.2012.08.100. [2] B. A. Pint, J. A. Haynes, K. A. Unocic, and Y. Zhang, “The effect of water vapor and superalloy composition on thermal barrier coating lifetime,” Proc. Int. Symp. Superalloys, pp. 723–732, 2012. [3] L. Mahfouz, B. Marchand, V. Guipont, F. Coudon, and V. Maurel, “Driving forces in thermal barrier coatings blistering,” Materialia, vol. 28, p. 101728, May 2023, doi: 10.1016/j.mtla.2023.101728. [4] Mahfouz, L., Maurel, V., Guipont, V., Marchand, B., El Hourany, R., Coudon, B., Mack, D.E., Vaßen, R. “Thermal Barrier Coatings in burner rig experiment analyzed through LAser Shock for DAmage Monitoring (LASDAM) method”, Under review, Journal of European Ceramic Society (2024)

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hal-05069688 , version 1 (15-05-2025)

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  • HAL Id : hal-05069688 , version 1

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Eliott Degouilles, Vincent Guipont, Vincent Maurel, Basile Marchand. Study of Thermal Barrier Coatings in Water Vapor Environment using the LASDAM methodology (LAser Shock for DAmage Monitoring). HTCPM 2024, Jun 2024, Les Embiez, France. ⟨hal-05069688⟩
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