Closed Field Unbalanced Magnetron Sputtered Solid Lubricant/Ceramic Coatings For Improved Wear Resistance of Bushing and Gear Materials

Increased wear life of bushings and gears in a high-pressure Navy gear pump will result in increased pump reliability and reduced refurbishment costs. Wear of silver-impregnated carbon (C/graphite (Gr) bushings against stellite gears results in reduced pump performance, generation of wear debris, displacement of the gears, and eventual pump failure. Technology Assessment and Transfer, a firm with expertise in novel tribocoatings, proposes two innovative solutions based on closed field unbalanced magnetron sputtering: 1) dispersed solid lubricant (e.g, diamondlike carbon, boron nitride) "islands" within a hard ceramic (e.g., boron carbide, silicon carbide) coating matrix and 2) ceramic coatings that will form lubricious oxide/hydroxide surface layers after reaction with the water working fluid. These solutions offer solid lubrication and potential for lubricant refurbishment (through water entrapment) to the bushing/gear interface, while still providing a hard, wear-resistant ceramic matrix. Alternate metallic materials for the bushing/gear tribosystem, that will not gall or seize in the event of coating wear, are also proposed. Coatings will be evaluated by immersion in static water, scratch adhesion, particle erosion, and rotating-disk wear tests in water. The best performing coating will be demonstrated on bushing and gear components.