Interfacial Microstructure and Properties of Antifriction Copper/Steel Cladding Composites Fabricated by Vacuum Diffusion Bonding

Antifriction (AF) copper/steel cladding composites combine the tribological properties of copper alloys with the high strength of steel, making interfacial bonding central to their performance. A Cu–2Ni–7Sn–10Pb AF alloy was joined to 45 steel by low‐pressure vacuum diffusion bonding. Using this fixed‐composition system, we examined how bonding temperature and holding time regulate interfacial elemental redistribution, Pb‐rich phase accumulation, transition‐layer development, and shear response. Interfacial elemental distributions changed substantially with bonding temperature, and heterogeneous Ni enrichment became pronounced at and above 900 °C. Bonding at 900 °C for 120 min produced an EPMA‐derived transition‐layer width of (1.60 ± 0.62) μm and a shear strength of 162 MPa. Across the investigated processing conditions, the EPMA‐derived interfacial transition‐layer width and shear strength showed a positive, although scattered, association. This trend indicates that transition‐layer development contributes to the shear response together with Pb‐rich interfacial coverage and local continuity. Bonding at 900 °C for 120 min provided a favorable combination of interface development and mechanical performance, establishing a quantitative basis for broader multivariable validation.