Water-lubricated behaviour of AISI 440C stainless steel and a DLC coating for an orbital hydraulic motor application

E. Strmčnik, F. Majdič, M. Kalin

Tribology International. Vol.131, March 2019, p. 128-136.


The low-speed, high-torque, orbital hydraulic motor[SPAN][SPAN] is a component that often uses mineral oil to convert hydraulic energy into the rotational motion[SPAN] of a shaft. The main purpose of our research was to investigate the possibility of using water, which is a much less environmentally damaging working fluid than oil. The limitations of water lubrication were overcome with an appropriate surface-engineering approach. The surface coated with diamond-like carbon[SPAN] (DLC) significantly reduced both the friction and the wear. The lowest coefficients of friction in this study, taking into account all the tested parameters, were obtained when the stainless-steel/DLC (SS/DLC) contact was tested in water. The friction of the SS/DLC in water was even lower than the friction of the SS/DLC or SS/SS contact in oil. Furthermore, the wear coefficient of the SS/DLC in water was comparable to the wear coefficient of the SS/SS in oil. The surface hardness, surface roughness and applied force were also varied, but they did not play such an important role as employing the DLC coating. The SS/DLC contact can thus be considered as a very promising solution for an orbital hydraulic motor from the tribological and environmental points of view.

URL: https://doi.org/10.1016/j.triboint.2018.10.032

Keywords: DLC Friction Stainless steel Water lubrication Wear

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