Researchers have developed a new Al10Cr28Co28Ni34/Ag high-entropy alloy composite coating that achieves 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 in low-viscosity aviation kerosene. The work, published in the journal Tribology Advances, addresses the combined wear and cavitation erosion damage that plagues friction pairs in aero-engine fuel pumps.
The fuel pump is often described as the heart of an aero-engine, and its performance and reliability directly affect flight safety. Inside the pump, the thrust bearing supports axial loads from the gears, maintains positioning accuracy, and provides sealing. However, aviation kerosene has extremely low viscosity, making it difficult to form a continuous and stable oil film at the contact interface under high-speed rotation. This leads to lubrication failure, bearing wear, and cavitation erosion, ultimately reducing fuel delivery efficiency.
Existing coating materials, such as bonded solid lubricating coatings (BSLCs), can mitigate wear under oil-starved conditions, but they struggle to simultaneously provide cavitation erosion protection. The key difficulties include insufficient strength and poor heat resistance of traditional organic resin matrices, which are prone to fracture under intense impact loads and cavitation heat. Additionally, substantial property mismatch between the matrix and lubricating phases leads to incompatible deformation behaviors, causing cracking at phase boundaries and accelerating the selective removal of lubricant fillers. Conventional materials also find it hard to balance friction reduction, wear resistance, and cavitation erosion resistance.
The new approach leverages the structural compatibility between the Al10Cr28Co28Ni34 high-entropy alloy (HEA) and silver (Ag). Both phases share a face-centered cubic (FCC) structure, which provides abundant slip systems that promote slip under shear forces and accommodate greater deformation under impact loading, thereby reducing friction and dissipating impact energy. The Al10Cr28Co28Ni34 HEA, owing to its four core effects, possesses high work-hardening capacity and substantially higher strength than conventional FCC metals, confining deformation and providing excellent cavitation erosion resistance. The composite coating was fabricated via high-velocity oxygen fuel (HVOF) spraying. Benefiting from the FCC/FCC structural compatibility, the coating exhibits similar response behaviors when subjected to external forces such as friction and impact. Combined with the rolling effect of spherical particles formed in situ at the friction interface, the coating achieves synergistic lubrication, wear resistance, and cavitation erosion protection.
These findings offer a new perspective for addressing the common challenge of combined wear and cavitation erosion damage in friction pairs of aero-engine fuel pumps. The research, detailed in the study available at https://doi.org/10.3724/trad-20260019, was financially supported by the National Science and Technology Major Project (Grant No. J2022-VI-0006-0037), the National Natural Science Foundation of China (Grant No. 52175200), the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB0470102), the Youth Innovation Promotion Association of the Chinese Academy of Sciences (Grant No. 2020416), and the Longyuan Youth Talent Project. The implications for the aviation industry are significant: improved fuel pump reliability and efficiency can enhance flight safety and reduce maintenance costs. For the broader tribology community, the FCC/FCC structural compatibility design strategy opens new avenues for developing coatings that combat multiple damage mechanisms simultaneously. As the industry seeks more durable and efficient components, this advancement represents a meaningful step forward. For those interested in the commercial potential of such innovations, Chuanlink Innovations focuses on fostering innovation and facilitating the journey of ideas from inception to realization.
