The Effect of High-Temperature Water Vapour on Degradation and Failure of Hot Section Components of Gas Turbine Engines

Abstract

For the past decade, the aviation industry has been adopting sustainable aviation fuels (SAF) for use in aircraft to reduce the impact of aviation on climate change. Also, some nations look to SAF as an option for energy security for their military fleets. Understanding the critical impact of alternative fuel sources on hardware will provide the gas turbine industry with strategic options in sustainability and maintainability of the existing and new fleets. The alternative fuels with high hydrogen/carbon ratio (H/C) (such as synthetic paraffinic kerosenes (SPK)) could produce more water vapour content than the conventional jet fuels upon combustion, and this increased water vapour level could exert a significant impact over the long-term durability on hot section components such as the substrate blades, oxidation resistant coatings, thermal barrier coatings (TBCs), environmental barrier coatings (EBCs), resulting in an accelerated degradation of the turbine components. The possible detrimental effect of high-temperature water vapour on degradation and lifespan of hot section components was examined. Examples were specifically given on degradation and spallation of thermally grown oxides (TGO), formation of non-protective oxides and ceramics topcoats in TBCs. Results show that water vapour can lead to volatilization of TGO (Al2O3), and is responsible for the formation of non-protective oxides in both Pt-modified β-NiAl and MCrAlY coatings, leading to their early spallation. However, water vapour does not appear to directly affect the ceramic topcoat of the TBC. For EBCs coated on SiC-based substrates, the substrate recession via silica (TGO) volatilization was reviewed. These EBCs were observed undergoing degradation in highly hostile environments, e.g., constantly operating under high temperatures, pressures, and velocities condition in the presence of water vapour steam. The review intends to provide a perspective of high-temperature water vapour effect on the EBCs’ topcoat properties such as durability, degradation, crack nucleation and crack growth, and possible guidance for mitigating these degradation effects.

Health and Durability of Protective and Thermal Barrier Coatings Monitored in Service by Visual Inspection

“…It gradually loses its protecting properties, and the structure of the base material is eventually weakened. The described degradation process is common for MCrAlY coatings [62][63][64], but it advances very quickly in this military turbofan due to high thermal stress.…”

Design of newly developed burner rig operating with hydrogen rich fuel dedicated for materials testing

“…The silicon is usually used for protection against water vapour in this application (Chen et al, 2021).…”

In Situ High-Temperature Tensile Fracture Mechanism of PS-PVD EBCs

“…To ensure their smooth operation and maintain a certain thermal efficiency, such components must possess excellent performance in terms of high temperature resistance. The temperature bearing capacity and the service lifetime of hot-end components can be improved using environmental barrier coating technology [1,2]. Environmental barrier coatings (EBCs) have good high-temperature corrosion resistance and are generally composed of complex multilayer structures, including bonded metal layers and ceramic layers [3].…”