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 sources. 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 hardened with WC/Co-Cr, which resists degradation only when there is no sand present. Thus, bearing lifetimes fall far short of the desired 5-10 years lifetimes. This project will develop a diamond-hardened WC/Co-Cr nanocomposite, in which a compositionally-graded layer of diamond nanoparticles is bonded to a nanostructured WC/Co-Cr substrate. A tough Co-Cr binder phase will be used for both the hard WC and the superhard diamond particles, thereby ensuring good fracture resistance of the nanocomposite. A high-pressure sintering technology will be used to produce the desired nanocomposite. To reduce raw-material cost, and to avoid the use of strategic metals such as W and Co, a modified composition ¿ a diamond-hardened TiC/Ti alloy ¿ also will be investigated. Commercial Applications and other Benefits as described by the awardee: For geothermal applications, the nanocomposite should resist coating spallation over the long term. Other commercial applications for diamond-hardened WC/Co-Cr and TiC/Ti-alloy nanocomposites include machine tools, drill bits, and wear parts. The advantages derived from a nanocomposite structure include higher hardness and compressive strength as well as improved fracture toughness.