Composition-load coupled transition mechanism of friction behavior in dual-ceramic (B₄C-SiC) reinforced Cu-based composites

This study elucidates the composition and load-driven transition mechanism of friction behavior in B₄C/SiC synergistically reinforced Cu-12Sn-2Ni composites fabricated by hot-press sintering. By varying the B₄C/SiC ratio and applied load, the composite with an equal ratio (B5S5) exhibited the most balanced mechanical properties (hardness 297 HV, compressive strength 438 MPa) and the most stable tribological performance. Under low-medium loads (20-50 N), the friction behavior was mainly governed by the structural continuity of the matrix and SiC-dominated load-bearing effect, leading to mechanical wear control. As the load increased to 80 N, the enhanced oxidation activity of B₄C triggered the formation of a dense CuO-B₂O₃ composite film, marking a transition of the dominant wear mechanism from mechanical abrasion to oxidative protection. XPS and worn surface analyses confirmed that CuO provides structural support while lubrication mainly arises from Cu-coated graphite and Cu-coated MoS₂; B-O species may contribute to stabilizing the tribo-layer. The synergistic coupling between ceramic composition and applied load thus determines the frictional regime and adaptive surface evolution. This composition-load coupling mechanism provides a fundamental strategy for designing adaptive, high-performance Cu-based composites operating under severe service conditions. This work also provides the first systematic demonstration of the coupled influence of ceramic composition and external load on adaptive tribo-film evolution in Cu-based composites.