Comparative Tribological Performance of Composites, Superalloys, and Ceramics for Extreme Environments

The rising demand for efficiency and sustainability in the aerospace sector requires the development of advanced materials capable of resisting extreme thermal and mechanical conditions. This is especially critical in gas turbine engines, where the performance of various assemblies is limited by their mechanical and tribological properties, making material selection crucial. This represents a major challenge for sealing systems, as clearance control and wear resistance remain key to engine performance and durability. Despite the widespread use of conventional polymers, superalloys, and ceramics in current engines, each exhibits performance limitations that restrict its application across the full spectrum of engine operating conditions. Thus, the objective of this research is to develop a design map for sealing interfaces by correlating operating conditions, microstructure, and wear behaviour of sealing materials across representative engine environments. Candidate materials, including polymer composites, nickel- and cobalt-based superalloys, advanced ceramics such as silicon carbide, and carbon–carbon composites, were evaluated against Inconel 718 counterfaces under representative sliding and fretting conditions spanning temperatures from −80°C to 800°C, together with surface characterization, to identify the wear mechanisms responsible for material degradation, helping guide the selection of materials for more durable sealing systems. Inconel 718, despite being one of the most widely used alloys in gas turbine engines, exhibits the highest friction coefficients and wear across a range of temperatures. It is more sensitive to temperature-driven wear than other materials, highlighting both its function as a benchmark and its tribological limitations in extreme sealing interfaces. On the other hand, polymers and composites exhibited low friction at lower and intermediate temperatures, but their use is limited at elevated temperatures due to degradation, whereas ceramics maintained thermal stability across the test temperature range, showing their potential in extreme environments. Overall, this research helps develop a materials design map for sealing interfaces, aimed at extending component lifespan, reducing leakage, and improving thermodynamic efficiency. These advancements support the aerospace industry's efforts to improve the reliability and sustainability of future propulsion systems.