Interactive Effects of Lubricant Type and Sliding Distance on the Tribological Behavior of Aluminium 6061 Against SKD11 Steel

Abstract

This study investigated the effects of lubricant formulation and sliding distance on the tribological behavior of Aluminum 6061 coupled with SKD11 steel under a constant normal load of 10 N. Sliding distances of 100, 1000, and 5000 m were tested under three lubrication regimes: dry contact, waste cooking oil (WCO)-based biolubricant, and WCO-based biolubricant containing 0.15 wt% TiO₂ nanoparticles. Tribological performance was evaluated using the coefficient of friction (COF) and wear rate, while Two-Way ANOVA assessed the significance of the main factors and their interaction. The TiO₂-enriched biolubricant produced the lowest COF (0.1081–0.1311), corresponding to a maximum reduction of 73.1% compared with dry friction, and reduced the wear rate to 1.48 × 10⁻³ mm³/N·m at 5000 m, indicating approximately 95% improvement in wear resistance. ANOVA confirmed that lubricant type significantly affected tribological performance (p < 0.05). These improvements were attributed to a more persistent boundary lubrication layer and protective tribofilm formation promoted by TiO₂ nanoparticles, demonstrating its potential as an environmentally friendly lubricant for aluminum-based manufacturing applications.