A research team has developed a high-entropy alloy composite coating that simultaneously provides lubrication, wear resistance, and cavitation erosion protection in low-viscosity aviation kerosene. The work, published in Tribology Advances, addresses a persistent challenge in aero-engine fuel pumps, where thrust bearings operate under oil-starved conditions that cause wear and cavitation damage.
The coating, designated Al10Cr28Co28Ni34/Ag, was fabricated using high-velocity oxygen fuel (HVOF) spraying. Its design exploits the face-centered cubic (FCC) structure shared by both the Al10Cr28Co28Ni34 high-entropy alloy (HEA) and silver. Because both phases have the same crystal structure, they deform similarly under friction and impact, reducing stress concentrations at phase boundaries that typically lead to cracking and material loss in conventional coatings.
Test results in aviation kerosene showed a friction coefficient below 0.1, a wear rate approaching zero, and a cavitation erosion mass loss rate of less than 0.1 mg per hour. The researchers attribute this performance to the formation of spherical particles at the friction interface, which roll between surfaces and contribute to a rolling-sliding mechanism. The HEA provides load-bearing capacity and work hardening, while silver acts as a low-shear solid lubricant.
The findings, detailed in the study available at https://doi.org/10.3724/trad-20260019, offer a new strategy for protecting fuel pump friction pairs. Existing bonded solid lubricating coatings can reduce wear under oil-starved conditions but often fail under cavitation because their organic resin matrices have insufficient strength and heat resistance. The new coating's all-metallic FCC/FCC design avoids these limitations.
For the aviation industry, the implications are significant. Fuel pumps are critical to engine reliability, and wear or cavitation erosion can reduce fuel delivery efficiency and compromise flight safety. A coating that resists both damage modes could extend component lifetimes, reduce maintenance, and improve operational readiness. The research was supported by the National Science and Technology Major Project, the National Natural Science Foundation of China, the Chinese Academy of Sciences, and other programs.
Beyond aviation, the FCC/FCC compatibility concept may be adapted to other tribological systems where low-viscosity lubricants and cavitation are present, such as in marine or industrial pumps. The study underscores how structural matching between coating phases can unlock combined properties that are difficult to achieve with conventional material designs.
