Low temperature Si-DLC coatings on fluoro rubber by a bipolar pulse type PBII system

Abstract

Diamond-like carbon (DLC) films have been attractive materials because of their excellent mechanical properties such as high hardness, low friction coefficient, high wear resistance and more. In order to spread the application of the DLC coatings for polymer materials, it is necessary to make the temperature go down during the coating process. Our group has been studying DLC coatings on several materials with bipolar pulse type PBII (plasma based ion implantation) systems, which consist of positive and negative (or bipolar) pulse generators and a timing controller. Recently we have introduced a new bipolar pulse generator, whose slew-rate is several times larger than that of previous generators, and a controller which can make a very short pulse less than 1 μs. Using the pulse generator and controller, we have tried to make Si incorporated DLC (Si-DLC) coatings on fluoro rubber, which is widely used in many industries, at low temperature. Using the new pulse generator and controller, we can make very short width positive pulse of about 1 μs, and reduce the temperature during Si-DLC coating to about 30 K. The lower temperature makes fewer folds on the sample surface. By using optical indentation microscope system, Meyer hardness (H M) of uncoated and Si-DLC coated fluoro rubber was obtained and the value of H M for Si-DLC coated rubber is about 1.4 times larger than that of uncoated rubber. Coefficient of friction of Si-DLC coated rubber was 0.2 to 0.25 and drastically decreased from 1.3 to 1.9 of uncoated rubber. Wear of uncoated fluoro rubber is apparent, however, wear of Si-DLC coated rubber cannot be observed, except for the creep effect of fluoro rubber substrate. The counter SUJ2 ball surfaces also showed almost no wear. Si-DLC coating can make the tribological property of fluoro rubber to low friction and less wear. Si-DLC coatings are very useful in many applications.