Silicide-Strengthened Steel - A New Method of Wear Protection within Nuclear Environments

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Cobalt-based (Co) steel alloys are extensively used in nuclear reactors, particularly in the valves and pumps employed in water-cooled reactors. This is because they provide outstanding wear resistance, and so improve component life and reduce maintenance requirements. However, these alloys are expensive, and also raise the radiation exposure of workers at nuclear utilities, due to the formation of Cobalt-60, a gamma-emitting radioactive isotope. For this reason, replacing Co-based hardfacing alloys in future nuclear reactors is highly desirable in terms of health and safety and cost, as well as long-term decommissioning. To date, however, alternative materials such as iron (Fe)- and nickel (Ni)-based alloys have not been able to match the outstanding properties of Stellite 6, a well-known Co-based alloy for hardfacing applications (i.e. applications where wear is of particular importance). In response to the EPSRC call for feasibility studies related to energy research, we propose to explore the manufacturability of novel silicide-strengthened stainless steels in order to deliver a new class of Co-free hardfacing materials for nuclear components, with high galling- and corrosion-resistance. We have discovered a new class of Fe-based alloys for hardfacing applications only very recently, providing a real and valuable opportunity to finally have a material system that can match Co-based alloys in their wear and corrosion performance, while also offering great cost advantages and reduced exposure risk for nuclear utility workers. Success in demonstrating the viability of this class of material, as proposed here, could further have great impact in many other areas where high-strength stainless steel solutions are required (such as in highly corrosive environments in the petrochemical industry).