Diamond-Hardfaced WC/Co-Cr Nanocomposites for Extended Service Life of Pump Bearings in Geothermal Wells

Renewable energy sources include electrical generators driven by steam from geothermal wells. To exploit this resource, submersible pumps with extended service lives are required to improve the economics of today¿s geothermal systems. A major problem is corrosive wear experienced by the pump bearings, when the lubricating brine becomes contaminated with fine sand particles. Typically, the bearings are hardfaced with WC/Co-Cr, which can resist degradation only when no sand is present. Thus, the bearings fall far short of the desired 5-10 years lifetimes. This project will develop diamond-hardfaced carbide-metal nanocomposites, in which a compositionally-graded layer of diamond nanoparticles is bonded to a nanostructured carbide-metal substrate. The graded coating/substrate interface resists coating spallation over the long term, even when the original geothermal brine becomes contaminated with entrained sand particles. Phase I fabricated a diamond-hardfaced WC/Co-Cr nanocomposite, in which a functionally-graded layer of diamond nanoparticles was bonded to a nanostructured WC/Co-Cr substrate. In Phase II, extensive materials characterization and mechanical properties studies will be performed.Commercial Applications and other Benefits as described by the awardee: The nanocomposite structure would exhibit mechanical properties advantages that include higher hardness and compressive strength, as well as improved fracture toughness. Beyond the application to geothermal wells, other potential commercial applications for diamond-hardfaced nanocomposites include machine tools, drill bits, and wear parts.