High Toughness Cermets for Molten Salt Pumps

Concentrated solar power has been identified as a clean process for the generation of electricity that is calculated to achieve cost competitiveness with conventional generation with systems operating at over 700⁰C. The high temperature and the corrosive properties of the heat transfer fluid and thermal energy storage media represent an extreme environment for concentrated solar power components. New materials and designs offering long life performance and lower cost are required for impellers, bearings and seals used to pump the molten chloride salts used. This project will validate the application of ultra-high toughness hierarchically designed metal matrix ceramic nanocomposite materials for molten metal pump impellers, seals, and bearings. Metal matrix ceramic nanocomposite materials offer very low friction in poorly lubricating fluids, and are extremely erosion and wear resistant, similar to diamond like carbon and chrome coatings, in a structural material that has mechanical properties equal to tool steel. These materials are comprised of a repeating nanocomposite unit encapsulated in a high toughness, corrosion resistant binder phase, and combine the best properties of metals and ceramics, providing high wear and erosion performance and toughness required for durable bearing, impeller and sealing elements, with the ability to withstand extreme stresses such as hot salt immersion and salt freezing and melting without failure. Phase 1 of this program will test these materials in molten chloride salt environments to verify their performance and cost effectiveness leading to the fabrication of low maintenance, durable, and reduced energy (through reduced friction) pumps for concentrated solar power systems. Corrosion resistance, static and dynamic, at temperature in molten salt and mechanical properties will be compared to current materials. Capability, quality and cost assessments of the manufacturing process will be completed during fabrication of typical parts. Pump manufacturers will provide guidance. Phase II will include the fabrication of prototype parts, specific application qualification testing and preparation of production processes and documentation. Pump manufacturer customer relationships and agreements will be established. The products developed in this program will be only one application for metal matrix ceramic nanocomposite materials. This new class of very hard and tough materials provide a platform technology to solve bearing and wear problems in commercial and military applications, in turbines, heavy equipment, material handling equipment and others. Wear and corrosion cost an estimated $1.2T annually in repair and replacement costs and unplanned downtime. Metal matrix ceramic nanocomposite materials are enabling for reducing corrosion, friction and wear in mechanical systems.