Assessment of the Tribological Behaviour of Self-Lubricating Metal Matrix Composites Developed for Circular Saw Guide Pad Applications

The development and performance of self-lubricating Cu-Fe-based composites produced via powder metallurgy are examined as an advanced alternative to conventional Babbitt alloy for guide pad applications in high-speed circular saw systems. The proposed composite addresses the inherent limitations of Babbitt, particularly its low mechanical strength and poor wear resistance under high contact pressures, aiming to improve durability and operational reliability. A baseline Cu-5 vol.% Ni-coated graphite (NCG)-6 vol.% CaF₂ composite was reinforced with incremental Fe additions (12–52 vol.%) to enhance mechanical strength while preserving favorable tribological properties. The composites were characterized through pin-on-disk and dry sand rubber wheel (DSRW) wear tests, complemented by the characterization of their mechanical properties (hardness and tensile testing) and detailed microstructural features using SEM/EDS. The results demonstrate that increasing Fe content significantly improves hardness, yield strength, and wear resistance, with the composite containing 42 vol.% Fe achieving the optimal performance balance. This composition exhibited nearly a twofold increase in hardness and an approximately threefold increase in yield strength, along with a 94% reduction in sliding wear during pin-on-disk test and an 81% reduction in abrasive wear compared to Babbitt. These improvements are attributed to the enhanced load-bearing capacity of the Fe-reinforced matrix and the formation of a stable oxide-rich tribolayer that effectively limits direct surface interaction and suppresses material removal. In contrast, excessive Fe content (52 vol.%) led to brittle oxide formation and increased wear due to crack propagation and delamination, confirming the existence of a critical reinforcement threshold. Semi-industrial testing further validated the superior performance of the optimized Cu-Fe-based composite. Compared to Babbitt, the optimized composite demonstrated reduced power consumption and negligible material transfer to the saw blade, indicating improved tribological efficiency. Surface morphology analyses of the guide pads revealed that while Babbitt guide pad experienced severe material loss, the Cu-Fe-based composite maintained a smooth and coherent contact surface with minimal damage. Overall, the Cu-42 vol.%Fe-5 vol.%NCG-6 vol.%CaF ₂ - composite emerges as a highly effective and durable replacement for Babbitt guide pads, offering superior wear resistance.