Tribological response of epoxy composite lining filled with zirconia and fly ash under dry sliding conditions

Epoxy-based composite linings are increasingly considered for wear mitigation in oil and gas well casing applications. This study systematically evaluates the tribological performance of a ceramic-filled epoxy composite lining reinforced with zirconium oxide particles, fly ash particles, and short glass fibers under dry sliding conditions. Full-scale experiments were performed using a testing rig at side loads of 500, 700, and 1000 N and rotational speeds of 65, 115, and 154 rpm. The composite lining exhibited average specific wear factors ranging from 0.3 to 2.81 × 10⁻⁸ MPa⁻¹ under moderate load conditions, and up to 12.5 × 10⁻⁸ MPa⁻¹ at 1000 N and 154 rpm. Worn surface characterization revealed that, under moderate conditions, zirconia particles remained embedded and acted as load bearing two-body abrasives, effectively shielding the epoxy matrix. Simultaneously, fractured fly ash particles contributed to the formation of a protective third-body layer. Under severe load conditions, thermal softening of the epoxy matrix led to zirconia and short glass fiber pull-out, resulting in a transition to a more aggressive wear regime dominated by adhesive matrix wear and three-body abrasion from hard debris. These results highlight the role of ceramic fillers in enhancing wear resistance and governing wear mechanisms, providing insight into the performance limits of ceramic-filled polymer composite lining for demanding applications.