Tribological properties of gold matrix composite coatings with carbon nanocapsules containing ionic liquid lubricants

Self-lubricating, gold matrix composite coatings were produced by electrochemical codeposition of carbon nanocapsules filled with ionic liquid (IL) from a colloidal galvanic bath on a nickel electrode. The tribological response of the composite coatings was analysed under sliding conditions against an alumina counterpart. The incorporation of carbon nanocapsules in the coatings decreases the coefficient of friction (CoF) by the release of the IL through a mechanical triggered mechanism. This is based on the cyclic loading of the coating that produces the smearing of gold and breaks the lubricant nanocontainers allowing for the IL to reach the contact surfaces. Lifetime of the galvanic coating, limited by the upsurgence of the nickel substrate when the gold locally breaks, was defined to be around 2.500 cycles while the lifetime of the self-lubricating composite coating could not be determined in the present study (longer than 20.000 cycles).