Synergistic Influence of Compaction Pressure and Sintering Temperature on Microstructure Evolution and Tribological Properties of Cu-Fe-Si-Mn-Ni Alloys

Copper-based sintered composites are widely employed in brake lining applications due to their superior thermal conductivity, mechanical strength, and tribological stability. However, the combined influence of compaction pressure and sintering temperature on the microstructure and tribological performance of multicomponent Cu-Fe-Si-Mn-Ni systems remains insufficiently characterized. This study employed a two-stage experimental strategy: in Stage 1, all three compositional variants were fabricated and screened for wear performance across 48 specimens; Composition (iii) (77.8 wt% Cu, 16.7 wt% Fe, 3.3 wt% Si, 1.7 wt% Mn, 0.6 wt% Ni) was selected for comprehensive characterization in Stage 2 based on consistently superior wear performance and its Fe:Si ratio (83:17 at%) within the Fe₃Si thermodynamic stability field. The effects of four compaction pressures (100-175 MPa) and four sintering temperatures (700-850°C) on sintered density, microstructure, Vickers hardness, volumetric wear rate, and coefficient of friction (COF) were systematically investigated. Microstructural analysis by SEM and EDS revealed progressive Fe₃Si nucleation with increasing sintering temperature, complete dissolution of Ni into the Cu matrix, and preferential Mn segregation to inter-phase boundaries. The highest density (6.34 g/cm³) and hardness (85 VHN) were achieved at 125 MPa/700°C; however, this condition exhibited the most severe tribological degradation at 850°C, with wear rate reaching 32.8 × 10⁻⁵ mm³/Nm and COF rising sharply to 0.62, reflecting Fe₃Si coarsening-induced tribofilm instability. In contrast, the 150 MPa/800-850°C processing window delivered the most favorable integrated tribological performance: lowest wear rate (9.8-13.8 × 10⁻⁵ mm³/Nm), stable COF (0.56-0.63), thermally stable hardness (40-44 VHN), and adequate density (5.78-5.87 g/cm³), underpinned by the finest and most uniformly distributed Fe₃Si microstructure of all conditions investigated (mean cluster diameter: 8.2 ± 1.4 μm). These findings establish a process-microstructure-tribology framework and demonstrate that microstructural homogeneity is the primary determinant of integrated tribological performance in Cu-Fe-Si-Mn-Ni sintered composites.