Sliding friction, wear and tribofilm formation of silver films electro-plated on copper alloy sheets

This study is aimed at clarifying the mechanism of wear process for Ag plating through a one-way sliding wear test. The samples of different hardness Ag plating on copper alloys were prepared as coupon and embossment specimens, which simulated terminal contacts. During the sliding test, the contact resistance and the friction coefficient are measured. The surface and cross-section morphologies, roughness, tribo-film formation, and wear volume of the Ag films after wear tests were investigated and the wear mechanism was discussed. As results, the hard Ag plating film (120 Hv) exhibited higher contact resistance comparing to the soft Ag plating film (80 Hv). The soft Ag film delivered a larger wear scar on embossment and wider wear trace on coupon specimens compared to the hard one. The overall wear volume of hard Ag film was less than that of soft Ag film, which can be attributed to the fine crystalline structure of hard Ag. Moreover, the observation of tribofilms formed on the Ag films after wear tests suggested that a mixed-type of adhesive and abrasive wears occurred for both of soft and hard Ag films.