Improving Boundary Lubrication of Phenolic-Based Coatings via Rare Earth Compound-Promoted Transfer Film Growth

Polymer composite coatings are promising for tribological protection, with stable transfer films being key to their friction-reducing and anti-wear performance, yet the mechanism by which rare-earth compounds, known to enhance polymer tribological properties, regulate transfer film growth remains unclear. In this work, the tribological performance of phenolic resin (PF)-based coatings filled with lanthanum oxide (La2O3) and lanthanum fluoride (LaF3) was systematically investigated. The results demonstrate that the friction coefficients of 5La2O3/PF and 3LaF3/PF decrease to 0.024 and 0.031, representing a 79.66% and 73.95% reduction compared to pure PF, which compensates for the inadequacy of oil lubrication. Tribochemical analyses and characterizations of tribofilm structures confirm that complex tribochemical reactions involving rare-earth compounds occur, promoting the growth of a solid-lubricating tribofilm at the boundary lubrication interface. This work provides a theoretical foundation for the design of high-performance polymer lubricating coatings.