© 2007 Society of Vacuum Coaters 505/856-7188 59 50th Annual Technical Conference Proceedings (2007) ISSN 0737-5921 ABSTRACT A novel hollow cathode plasma immersion ion processing method is developed and used to deposit silicon containing diamond like carbon (DLC-Si) coatings inside a one foot long 304 stainless steel (304SS) pipe with 1.5 inch diameter and 0.065 inch wall thickness. A multilayer DLC-Si coating structure was deposited using a combination of carbon and silicon precursors starting with silicon-rich adhesion layer. Result shows that the interface between the substrate and ad- hesion layer contains silicon as well as substrate constituents. Within this interface, isolated crystalline structure embed- ded within amorphous matrix was present while deposited DLC-Si coating is amorphous. Data show that the layered DLC-Si coating structure not only improves the friction and wear performance of the internal surface of 304SS pipe but also improves the corrosion resistance. The hardness and modulus of the coating was measured at 19GPa and 138GPa, respectively. It is suggested that this new technology enables wide spread use of DLC based coatings to increase component life in applications where the internal surface of pipes are exposed to corrosive and abrasive environments especially in oil and gas industry. INTRODUCTION Diamond-like carbon (DLC) coatings have excellent properties such as high wear resistance, very low friction coeffcient and high corrosion resistance [1-3]. Because of these excellent properties, DLC coatings have attracted great attention for use in various applications in industries such as oil and gas, semiconductor, medical and automotive. In the oil and gas industry, DLC coatings are especially expected to improve the tribological and corrosion performance of components that experience extreme environments. For piping or tubing that delivers corrosive material, obviously the interior surface that is in contact with the corrosive material is the surface that must be coated. There are several methods available to deposit DLC based protective coatings at the outer surface of component such as chemical vapor deposition (CVD), physical vapor deposition (PVD), electroplating, fame spray and sol-gel. However, coating internal surfaces remains a challenge especially for large aspect ratio (length to diameter ratio) components and very limited information is available in literature. Investigation of DLC-Si Film Deposited Inside a 304SS Pipe Using a Novel Hollow Cathode Plasma Immersion Ion Processing Method T. Casserly, K. Boinapally, M. Oppus, D. Upadhyaya, B. Boardman, and A. Tudhope, Sub-One Technology, Inc., Pleasanton, CA Various methods of coating the interior surfaces of tubes have been attempted whereby the source material to be coated is inserted into the tube and then sputtered or arced off onto the tube [4,5]. It is reported that a chamber based plasma assisted chemical vapor deposition (PACVD) can be used to deposit coating on small aspect ratio components such as small hollow pins (15mm x 100mm) with a thin layer of DLC-Si [6,7]. In contrast to the work presented here where, these processes use a separate chamber and have a much lower deposition rates, so that much thicker flms, needed for corrosion and abrasion resistance, can not be deposited. This article demonstrates the potential of a new technology to deposit multilayer DLC-Si based flm on internal surfaces of pipes and presents microstructural, corrosion and mechanical performance data. EXPERIMENTAL Coating Deposition A novel hollow cathode plasma immersion ion processing method is developed and used to deposit silicon containing diamond like carbon (DLC-Si) flms onto the internal surface of a 304SS pipe. This method takes advantage of plasma ion immersion and hollow cathode plasma generated within the pipe itself allowing decomposition of precursor gases and subsequent deposition of DLC-Si based flms. As seen in Figure 1, this is done by negatively pulse biasing the pipe, which acts as the cathode, with anodes attached at the ends. A gaseous precursor is introduced and ionized causing a coating to be deposited on the pipe, with by-products pumped out [8]. Figure 1: Diagram of Process Set-up [8].