Tribotechnical Properties of Copper-Based Antifriction Composites for High-Speed Friction Units of Printing Machines

Abstract

The tribotechnical properties of the Cu–(4–6) wt.% Ni–(1–1.5) wt.% Ti–(7–10) wt.% Al–(0.5–0.8) wt.% Si‒(5–8) wt.% CaF₂ antifriction composite were studied. The effect of tribofilms that form and evolve in the friction process in air at loads of 2.0 MPa and rotational speeds from 5,000 to 15,000 rpm on the tribological properties was analyzed. The evolution of dissipative tribofilms and the counterface occurs through a bifurcation mechanism with a transition to one of two attractors, depending directly on the high-speed loading modes. At speeds of 5,000–13,000 rpm, a continuous homogeneous lubricating layer forms on the contacting surfaces. Electron microscopy and elemental mapping of the tribofilm confirmed that the distribution of elements was uniform, promoting high antifriction properties and a sustained self-lubrication mode. With increase in the rotational speed to 15,000 rpm, the system exhibits a self-organization effect in the formation of a coarse heterogeneous tribofilm. This tribofilm loses its continuity and is an accumulation of phases, leading to a sharp decline in antifriction properties. The dual formation of tribofilms is decisively influenced by operating conditions, particularly the intensity of external energy. Depending on this energy, tribofilms show different structures and manifest in two functionally opposite types, transforming from antifriction films to friction ones, resulting in significantly different tribotechnical properties. Copper-based antifriction composites can be recommended as an effective alternative to cast bronzes for operation at rotational speeds of 5,000–13,000 rpm and loads of 2.0 MPa in the friction units of forming, printing, and offset cylinders in high-speed printing equipment.