Friction-reducing properties of stearic acid modification of the Cu2S film on the copper substrate

A simple two-step process was developed to fabricate the dual-layer films on copper substrate for the purpose of lowering friction. The Cu2S film was fabricated on the surface of the copper substrates by the hydrothermal reaction. A stearic acid overcoat was then prepared on surface of the Cu2S film. X-ray photoelectron spectroscopy, scanning electron microscopy, Fourier transform infrared microscopy and water contact angle measurements were used to analyze the morphological features, the chemical composition and the hydrophobicity of freshly prepared samples. Moreover, the tribological behavior of the dual-layer films was evaluated by sliding the films against a steel ball under 0.5 N normal load using a reciprocating ball-on-plate tribo-tester. It was found that the stearic acid overcoat on the Cu2S film led to a significantly decreased friction with greatly extended life.

► Cu2S thin film is fabricated on the copper substrate by hydrothermal reaction.
► Stearic acid is deposited on Cu2S film for dual-layer film.
► The dual film has the water contact angle as high as 145°.
► The dual film possesses low friction with extremely long duration.