Reduction of wear in critical engine components using ion-beam-assisted deposition and ion implantation

Ion-beam-induced decomposition of hydrocarbon precursors is an efficient method for the deposition of diamond-like carbon (DLC). A large area, high current beam of 1-10 keV N+ and N-2(+) ions is used to break up a hydrocarbon precursor, releasing a large fraction of the hydrogen and leaving an amorphous carbon-rich network. This capability has been applied to the improvement of the tribology of combustion engine components. The effect of an intermediate layer of silicon, reacted to form a metal silicide, on the adhesive and wear properties of DLC has been studied by reciprocating pin-on-flat testing under representative loading, lubricating and temperature conditions. A significant reduction in the wear rate is observed when compared with bare and DLC-coated pins without a bond coat. Further experiments were directed at assessing the effect of metal ion implantation on the performance of hard chrome-plated piston rings. Initial results from accelerated wear tests of small treated segments are presented. Samples were implanted with 120 keV yttrium and lanthanum ions at doses of 1 x 10(16) and 1 x 10(17) ions cm(-2). A significant increase in wear was observed at the higher doses. However, a marked improvement was observed in the wear properties of segments co-implanted with nitrogen or oxygen at similar ranges and doses, suggesting the formation of a compound phase which strengthens the material.