composite, titanium, pump, bearing, geothermal
Renewable energy sources include electrical generators driven by steam from geothermal sources. Typically, the bearings of submersible pumps used in geothermal systems are hardfaced with WC/Co and WC/CoCr composites. To enhance bearing performance, we have developed a TiC/Ti composite, with a functionally-graded hardfacing. This new material resists degradation in geothermal brine much better than WC/Co and exhibits less wear or no wear at all, even if sand is present in the brine. The TiC/Ti composite also reduces raw materials costs, avoids the use of strategic metals, such as W and Co, and increases lifetimes of bearings in geothermal pumps. Ti-matrix alloys are more resistant to corrosion in salt water and hot corrosion in brine than Co or Co-Cr matrix alloys, particularly when the brine contains H2S, CO2 and sulfate acids. Besides, the developed TiC/Ti-matrix composite has lower friction coefficient and experiences reduced wear compared with WC/Co-matrix composite. If the alloy is hardfaced with functionally-graded diamond, the wear resistance is dramatically enhanced, so that this material can be used for drill bits as well.