Case study: The effect of an amorphous hydrogenated carbon-coated gear-wheel on a hydraulic orbital motor’s efficiency over time

This case study examines how the application of an amorphous hydrogenated carbon coating to gear-wheels affects the volumetric and mechanical efficiencies of the hydraulic orbital motors into which the gear-wheels are assembled. The efficiencies over time of these orbital motors are compared with the efficiencies of orbital motors, which were assembled and tested with standard (uncoated) gear-wheels. Comparisons are based on experimental data, accumulated over 3000 h of steady-state tests, divided over six motors with a duration of 500 h each. The paper examines the surface roughness characteristics of amorphous hydrogenated carbon-coated gear-wheels before and after coating, the measured magnitudes and positions of wear on the contact surfaces of the coated and uncoated gear-wheels after testing, and the observed differences in said wear utilizing scanning electron microscopic analyses. Finally, changes in the measured efficiencies of the orbital motors are examined, over the duration of the experimental tests, in order to consider the potential energy savings associated with hydraulic orbital motors assembled with coated gear-wheels.