Development of Novel Vanadium Carbide Coatings Using a 
Large Area, Non-Line-of-Sight Plasma Process, 18-9189

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Principal Investigator
James H. Arps

Inclusive Dates: 04/01/00 - 07/01/01

Background - Plasma immersion ion processing (PIIP) is a relatively new vacuum technology for the application of hard, wear-resistant coatings. Like conventional physical vapor deposition (PVD) methods, PIIP is used to deposit various coatings. The non-line-of-sight PIIP approach allows simultaneous treatment of large components and complex shapes without requiring component manipulation. Building on established capabilities in ion beam surface modification techniques, SwRI has committed to the advancement of PIIP technology. The recent availability of inexpensive, high-power, pulsed modulator equipment and the inherent scalability of PIIP lend an economy to this surface modification process that is difficult to match using other methods. The goal of the proposed research program is to help substantiate SwRI's position as the leading U.S. practitioner of PIIP for industry through the development of key next-generation PIIP coating compositions and approaches described below.

Approach - Research has been directed at the development of proprietary super-hard vanadium carbide (VC) and carbon-based multilayer coatings that can be applied in work for a diverse range of clients. This VC deposition capability has many immediate potential industrial applications due to the exceptional properties of VC and an established market for VC coatings. The combination of deposition processes to produce multiplayer coatings using the same set of equipment has demonstrated the versatility of the process overall and the ability to enhance and tailor coating properties, such as adhesion and toughness, to suit a wider number of industrial needs. A final objective has been to develop the means to apply both new and established coating formulations to high-aspect, down-hole geometries that are essentially inaccessible by other vacuum-based technologies.

Accomplishments - Successful completion of this project has helped to open up a range of new applications for PIIP in areas of light and heavy manufacturing, especially in the aerospace and automotive industries. For example, a number of potential and existing clients have inquired about treatment of inner diameters of tubes, a common "restricted geometry." Since the beginning of this work, the research team has believed that plasma generation inside the tube would be a challenging problem. A representative stainless steel cylinder (see below), 18 inches long by 7 inches in diameter, was coated with diamond-like carbon (DLC) via PIIP. The three light patches visible at the bottom of the tube correspond to areas masked by silicon-witness samples. Initial experiments showed that, while the coating thickness could change substantially (25 to 50 percent) along the length of the tube, the DLC hardness was consistent with previous work on planar samples and varied along the tube by a smaller amount (10 to 20 percent). Further efforts were able to reduce the degree of thickness nonuniformity and expended the range of restricted geometries to tubes up to 10 inches long and 5/8 inch in diameter. Several samples have been prepared for a major aerospace manufacturer interested in applying this technology to hydraulic components.

Diamond-like carbon-coated cylinder (18 inches length by 7 inches in diameter)

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