Wear and corrosion of cobalt-base alloys used in nuclear plants contribute significantly to the radiation exposure of plant maintenance personnel. An overview of an extensive EPRI program to develop iron-base alloys with resistance to adhesive (galling) wear and cavitation-erosion wear matching those of the traditional cobalt-base alloys is presented. Laboratory studies identified compositions with the desired resistance to wear and corrosion. Weld consumables, including gas atomised powder and homogeneous and metal-core wires, were produced. Weldability studies showed that multi-layer, defect-free deposits could be obtained using standard welding equipment. Gas-atomised powder has been used to hardface seats and discs of gate valves being exposed to extensive cycling under conditions found in the primary circuits of light water reactors. Examination of the valves and the valve trim, using diverse techniques, confirms the outstanding performance of the new alloys. Wire products and welding procedures suitable for field applications have been developed. Additional research, just getting under way, will evaluate these alloys in key nuclear plant valves and develop wire products and welding procedures for hydroturbine applications.
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