Effect of the substrate geometry on plasma synthesis of DLC coatings

Abstract

Diamond like carbon (DLC) coatings provide very good wear protection in application with machine elements like bearings, gears, shafts and chains. Ensuring the coating characteristics and reproducibility of DLC coatings on different geometries are major concerns in industrial application scale. Due to the change in the plasma intensity, the same coating process can result in different mechanical properties on different geometrical substrate shapes. In order to determine the influence of substrate geometry on the coating characteristics the plasma parameters, such as electron temperature and electron density should be determined. This study presents the effect of the substrate geometry on the plasma synthesis of hydrogen free (a-C) and hydrogen containing (a-C:H) DLC coatings deposited by magnetron sputter ion plating (MSIP) technology in an industrial coating facility. The electron temperature, plasma potential and electron density are determined by a Langmuir probe at two different substrate geometries, such that one of them has a planar and the other one has an angular surface, which corresponds to the geometries of a bearing and a gear, respectively. The adhesion and the mechanical characteristics, i.e. universal hardness and Young's modulus, of the DLC coatings are determined by scratch test and nanoindentation, respectively. The dependency of the mechanical characteristics on the plasma parameters for different geometrical surfaces is examined and the results are compared. The results show that depending on the plasma gas, either pure argon or mixture of argon and acetylene, the substrate geometry has a significant effect on mechanical properties and adhesion. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.