A new study published in Tribology Advances demonstrates that a high-entropy alloy composite coating can simultaneously provide lubrication, wear resistance, and cavitation erosion protection in aviation kerosene. The research, titled "FCC/FCC structural compatibility enabling synergistic lubrication, anti-wear and cavitation erosion of Al10Cr28Co28Ni34/Ag composite coating in aviation kerosene," addresses a critical challenge in aero-engine fuel pumps, where thrust bearings operate under severe conditions of low-viscosity fuel, high-speed rotation, and cavitation.
The fuel pump is often described as the heart of an aero-engine, and its reliability directly impacts flight safety. The thrust bearing inside the pump bears axial loads and maintains positioning accuracy, but aviation kerosene's extremely low viscosity makes it difficult to form a stable lubricating film. This leads to lubrication failure, wear, and cavitation erosion, ultimately reducing fuel delivery efficiency. Existing coatings, such as bonded solid lubricating coatings, can mitigate wear under oil-starved conditions but struggle to provide cavitation erosion protection due to insufficient matrix strength, poor heat resistance, and property mismatches between phases.
The new approach leverages the structural compatibility between the Al10Cr28Co28Ni34 high-entropy alloy (HEA) and silver (Ag), both of which have face-centered cubic (FCC) structures. This compatibility allows the coating to respond uniformly to external forces, such as friction and impact, reducing stress concentrations and cracking at phase boundaries. The coating was fabricated using high-velocity oxygen fuel (HVOF) spraying. In tests with low-viscosity aviation kerosene, the coating achieved a friction coefficient below 0.1, a wear rate approaching zero, and a cavitation erosion mass loss rate of less than 0.1 mg/h. These results are attributed to the synergistic effects of the FCC/FCC design, the load-bearing capacity of the HEA, the low-shear film formation of Ag, and the in-situ formation of spherical particles that promote a rolling-sliding mechanism.
The implications of this research are significant for the aviation industry. By addressing the combined damage from wear and cavitation erosion in fuel pump friction pairs, this coating could extend the service life of thrust bearings, improve fuel delivery reliability, and enhance overall flight safety. The study offers a new perspective on designing coatings that integrate multiple protective functions, potentially reducing maintenance costs and downtime. The full findings are available in the paper, with the DOI https://doi.org/10.3724/trad-20260019.
This work was supported by several funding sources, including the National Science and Technology Major Project, the National Natural Science Foundation of China, and the Strategic Priority Research Program of the Chinese Academy of Sciences. The research underscores the importance of material innovation in solving longstanding engineering challenges, particularly in extreme environments where conventional materials fall short.
