CCS and Power Systems
Crosscutting Research - Plant Optimization Technologies
Low Cost Fabrication of ODS Materials
Project No: FWP-60098
Powder Metallurgy (PM) processing technology covers most metallic and alloy materials and a wide variety of shapes. PM processing was originally developed and is used for manufacturing small-scale parts, but is often neither economical nor reliable for fabricating large-scale product. Typically, ferritic steel and oxide dispersoid powders are mechanically alloyed in a high energy mill over a period of at least twenty hours. The mechanically alloyed powder blend is poured into a steel can, which is evacuated and welded shut, then placed into a hot isostatic press (HIP) for consolidation at high temperature and pressure to near theoretical density. Once the resulting billet is stripped of the outer can, it undergoes a series of plate rolling or tube piercing/cross-rolling and heat treatment steps to form the finished plate or pipe geometry. The oxide dispersion strengthened (ODS) material is prone to picking up impurities during the extensive milling process; pore defects during HIPing; and dispersoid, inclusion, and/or pore alignment (stringering) during rolling, all of which degrade material properties at high and low temperatures.
One approach to enabling the full potential of ferritic ODS materials in advanced fossil energy power plant cycle is to reduce these defects and also reduce production cost by a new processing methodology. PNNL’s recent progress in friction stir welding of ODS alloys suggests that stainless steel and powder blend can be directly mixed and consolidated into full density rod and tube shapes via a one-step friction stir or shear consolidation process (SCP). This project will investigate this new powder metallurgy process, which has the potential to significantly reduce the cost of fabricating ODS products and enable their use in coal and other fossil fuel power plant applications.