A newly developed Al10Cr28Co28Ni34/Ag high-entropy alloy (HEA) composite coating has demonstrated exceptional synergistic lubrication, anti-wear, and cavitation erosion resistance in low-viscosity aviation kerosene, according to research published in Tribology Advances. The coating, fabricated via high-velocity oxygen fuel (HVOF) spraying, leverages the structural compatibility between two face-centered cubic (FCC) phases to achieve 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 address a critical challenge in aero-engine fuel pumps, where the thrust bearing must withstand axial loads and maintain sealing under severe conditions.
The fuel pump, often described as the heart of an aero-engine, relies on the thrust bearing to support axial loads transmitted from gears. Aviation kerosene's extremely low viscosity makes it difficult to form a stable oil film at the contact interface under high-speed rotation, leading to lubrication failure, wear, and cavitation erosion. Existing bonded solid lubricating coatings (BSLCs) can mitigate wear under oil-starved conditions but struggle to simultaneously provide cavitation erosion protection. The limitations stem from the insufficient strength and poor heat resistance of traditional organic resin matrices, which are prone to fracture under impact loads and cavitation heat, as well as property mismatches between matrix and lubricating phases that cause cracking and selective removal of lubricant fillers.
The researchers turned to metallic materials that exhibit both good lubricating properties and cavitation erosion resistance. They found that most such materials are predominantly FCC-structured, including solid lubricants like Au, Ag, and Cu, and cavitation erosion-resistant alloys such as aluminum bronze, nickel-aluminum bronze, and the Al10Cr28Co28Ni34 HEA. The abundant slip systems in FCC structures promote slip under shear forces and accommodate greater deformation under impact loading, reducing friction and dissipating impact energy. Owing to the four core effects of high-entropy alloys, the Al10Cr28Co28Ni34 HEA possesses high work-hardening capacity and substantially higher strength than conventional FCC counterparts, confining deformation from load impact and providing excellent cavitation erosion resistance.
Inspired by this, the study proposed an FCC/FCC structural compatible design, exploiting the compatibility between the Al10Cr28Co28Ni34 HEA and Ag to fabricate a composite coating that integrates lubrication, wear resistance, and cavitation erosion protection. The coating's similar response behaviors under external forces, combined with the rolling effect of spherical particles formed in situ at the friction interface, enable the synergistic performance. This approach effectively addresses the combined damage caused by wear and cavitation erosion in fuel pump friction pairs.
The research findings, detailed in the paper "FCC/FCC structural compatibility enabling synergistic lubrication, anti-wear and cavitation erosion of Al10Cr28Co28Ni34/Ag composite coating in aviation kerosene," offer a new perspective for enhancing the reliability and efficiency of aero-engine fuel pumps. By achieving near-zero wear and long-term cavitation erosion resistance in a single coating, this technology could significantly extend the service life of critical components and improve flight safety. The study was financially supported by the National Science and Technology Major Project, the National Natural Science Foundation of China, the Strategic Priority Research Program of the Chinese Academy of Sciences, and other programs. For more details, the full paper is available at https://doi.org/10.3724/trad-20260019.
