High throughput deposition of hydrogenated amorphous carbon coatings on rubber with expanding thermal plasma

Flexible hydrogenated amorphous carbon (a-C:H) thin film coated on rubbers has shown outstanding protection of rubber seals from friction and wear. This work concentrates on the potential advances of expanding thermal plasma (ETP) process for a high throughput deposition of a-C:H thin films in Ar/C2H2 plasma on nitrile butadiene rubber (NBR). The effect of the arc current on the microstructure, interfacial adhesion and tribological properties of the deposited a-C:H films on NBR is scrutinized. The temperature variation during the short ETP process is small and only yields sub-millimeter segmented a-C:H films, in consistence with a previously developed model. Increasing the arc current from 30 A to 75 A leads to smaller sizes of film patches (reduced from 940 mu m to 125 mu m), enhanced adhesion strength from 20.4 MPa to 91.8 MPa and higher hardness (from 5.5 GPa to 8.9 GPa) of the deposited a-C:H films on rubber. The tribological performance of the ETP a-C:H coated NBR is a compromise between the adhesion strength and hardness of the a-C:H films, with the coefficient of friction being reduced from about 1 (uncoated NBR rubber) to less than 0.25 of a-C:H film coated NBR. (C) 2014 Elsevier B.V. All rights reserved.