Application of Cr-X-N Thin Film to Improve the Tribological Properties of Environment Friendly Hydraulic Components
In this study, CrZrN film was deposited on AISI 4130 cylinder barrel and valve plate using a unbalanced magnetron sputtering. The tribological properties between a coated steel cylinder barrel and coated steel valve plate were evaluated by a custom-built disk-to-disk tribometer and the results were compared with those between a coated steel cylinder barrel and a conventional bronze valve plate. The lowest friction coefficients were observed between a coated steel cylinder barrel and coated steel valve plate and they were approximately one half of those between a coated steel cylinder barrel and conventional bronze valve plate in the range of testing up to 1600rpm. Coated valve plate and bronze valve plate showed a steady state of friction coefficient at approximately 0.03 and 0.06, respectively after about 1000 rpm, but steel valve plate without coating showed a continuous decrease in friction coefficient, which suggested that active wear is continuously occurring. By applying CrZrN coating on the commercial cylinder barrel and steel valve plate, much improved tribological results could be obtained, by a factor of approximately 2 in terms of friction coefficient than those from bronze valve plate. Under a tap water environment CrZrN coating appeared to perform better than CrSiN coating. Although further work to reduce the friction coefficient below 0.13 in the steady state after initial drop is still needed, possibilities of applying CrZrN coating to realize a water hydraulic pump were demonstrated through the present work.
Hyungsun Kim, Junichi Hojo and Soo Wohn Lee
S. Y. Lee et al., "Application of Cr-X-N Thin Film to Improve the Tribological Properties of Environment Friendly Hydraulic Components", Materials Science Forum, Vols. 544-545, pp. 657-660, 2007