Tribological Enhancement of Stir-Cast AA2219/TiC–Al₂O₃ - Si₃N₄ Hybrid Nanocomposites: Mechanism and Surface Layer Analysis

This work investigates the fundamental tribological behavior of stir-cast AA2219 aluminum alloy hybrid nanocomposites reinforced with TiC and Al₂O₃/Si₃N₄ nanoparticles. While traditional approaches emphasize property improvements, this study shifts focus toward understanding the mechanisms governing tribolayer formation, interfacial bonding, and thermomechanical interactions during dry sliding wear. Through pin-on-disc experiments (ASTM G99), SEM/EDS/XRD analyses, and statistical validation (ANOVA), the study uncovers how reinforcement-induced tribofilms stabilize sliding interfaces. The optimal composite (5 wt.% TiC + 3 wt.% Al₂O₃) showed a 69% reduction in wear rate, which correlates with dense, adherent tribolayer development. Over-reinforcement disrupted this tribofilm through nanoparticle agglomeration and third-body abrasion. Mechanistic interpretations—based on load transfer theory, dislocation pinning, and tribo-chemical layer evolution—reveal a reinforcement threshold critical for wear stability. This work contributes to tribology by providing insight into how ceramic hybrid nanoparticles influence interfacial stress distribution and tribofilm resilience, crucial for the design of tribo-functional aluminum composites.