Tribological behavior of dual-layer electroless-plated Ag–carbon nanotube coatings

Abstract

The tribological behavior of electroless Ag-plated carbon nanotube (CNT) dual-layer coatings was assessed and compared to that of the pure CNT coating. The motivation was to protect the surface of CNT coatings from wear by depositing a thin, soft Ag coating. The methods used for coating CNTs and Ag were spin coating and electroless plating, respectively. These coating methods were selected based on their simplicity and cost effectiveness. Wear tests were conducted by sliding the coatings against a stainless steel ball under a 10–30mN applied load. Results showed that the wear rate of the dual-layer coating was strongly dependent on the thickness of the Ag layer as well as the applied load. At a 10mN load and an Ag thickness of 65nm, the wear rate of the dual-layer coating was about 10 times less than that of the pure CNT coating. However, when the thickness of the Ag was decreased to 11.5nm, the wear rate was significantly higher. Also, the steady-state friction coefficients of the CNT and the dual-layer Ag–CNT coatings were in the range of 0.65–0.73 for all loads. A model of the wear reduction mechanism of the dual-layer Ag–CNT coating was proposed.