Observation of uniformity of diamond-like carbon coatings utilizing hollow cathode discharges inside metal tubes

Abstract

In this paper, the hollow cathode-plasma enhanced chemical vapor deposition (HC-PECVD) technique was used to deposit diamond-like carbon (DLC) coatings on the inner surface of 304 stainless steel (SS304) tubes with 30 mm in inner diameter and 40 cm in length. The uniformities of thickness, microstructure, mechanical properties, tribological performance of DLC coatings along the tube axis with the different frequency of power supply were studied. The results indicated that the frequency of power supply was an essential parameter to determine the uniformity of DLC coatings inside SS304 tubes. With the low frequency of power supply, the uniformity of DLC coatings along the tube axis was well. The uniformity of DLC coatings was poor with the high frequency of power supply, however, the deposition rate and mechanical properties were outstanding. The results confirmed that the uniformity of DLC coatings became better with the frequency of power supply decreasing.