High-temperature tribological performance of superalloys and silicon carbide: exploring ceramic materials for tribological interfaces in next-generation gas turbines

To address the environmental challenges associated with greenhouse gas (GHG) emissions in aviation, gas turbine engines must significantly reduce CO2 emissions. Achieving this will require a comprehensive redesign of engines to enhance thermal efficiency using materials that can withstand higher temperatures and pressures. This will increase the demand for high-performance materials with strong mechanical and tribological properties to prevent premature degradation of components. Additionally, understanding material interactions is crucial for effective tribological performance in engine assemblies like bearings, seals, and gears. Thus, the objective of this study is to comprehensively analyze the tribological behaviour of Inconel 718 when in contact with various counterfaces, including superalloys and ceramics, under conditions replicating those found in engine operations (at elevated temperatures of 450 °C and 800 °C under fretting conditions). This investigation focused on three selected counterface materials: a nickel-based superalloy (Inconel 718), a cobalt-based superalloy (Haynes 25), and a highly corrosion-resistant ceramic (silicon carbide). Overall, both superalloy counterfaces and the corresponding Inconel 718 surfaces demonstrated a reduction in wear, attributed to a transition in wear mechanisms from a gross-sliding regime at 450 °C to a stick regime at 800 °C; however, this transition led to an increase in friction force. In contrast, the silicon carbide counterface tested at 800 °C exhibited a gross-sliding fretting regime and friction force behavior similar to that observed at lower temperatures. Thus, the consistency in performance of silicon carbide in terms of friction and wear behavior compared to nickel-based and cobalt-based superalloys underscores its potential for further development in gas turbine engines.