Zhonghuai Wang, Michael Akkaoui, Tanury Industries, Lincoln,RI
This paper describes the PVD Diamond-Like-Carbon (DLC) coatings. Magnetron sputtering uses energized gas ions to bombard a target material (e.g. graphite or tungsten) and causes a reaction the energized ions to eject atoms of the target material to deposit onto the substrate. Meanwhile, the reactive acetylene gas is precisely metered into the chamber, the carbon and hydrogen atoms from the metal / gaseous plasma deposit onto the substrate to form Tungsten-doped DLC coating, often referred to as W-DLC or a-C:H:W which enhance wear resistance, low friction and reduced internal stress which improves adhesion. The paper compares the DLC properties between Closed-field-Unbalanced Magnetron (CFUBM) sputtering method which increases the ion current density at the substrate to increase the density of the coating and Rotary magnetron sputtering technique which improves the target utilization and extends target life. The effect of multiple types of sp molecular coatings forms a diamond crystal structure sp³ with high hardness and graphite crystal structure sp² which creates a high level of lubricity. The ratio of sp² to sp³ could be controlled by different coating parameters to make friction coefficient µ from 0.1 to 0.3 and hardness from 15GPa to 30GPa to satisfy different applications.