Development of cobalt-free hard-facing alloys for nuclear applications: 1984 progress

Cobalt-free hardfacing alloysare needed to replace cobalt-base AlloyNo. 6, used in nuclear valves, in order to reduce the radiation exposure of service personnel that is associated with cobalt 60. An analysis of the property requirements of nuclear hardfacingmaterials indicates that gallingresistance is a critical property which is generally not associated with cobalt-free alloys. A series of cobalt-free alloyswas selected for evaluation based on the available knowledge of wear and gallingbehavior of austenitic iron-base alloys. The experimental alloyswere evaluated for gallingresistance and for adhesive wear resistance in a crossed cylinder wear test in both air and deionized water environments at room ambient temperature. Tensile, impact, hardness and weldabilityproperties of the alloyswere also evaluated. An iron-base alloyhas been identified with gallingresistance properties equivalentto those of the AlloyNo. 6 in tests in deionized water and in tests in air at loads up to 275 MPa (40 ksi). The effects of variations in Mn, Si, Ni and N contents on the wear, mechanical, and welding properties, and on the alloymicrostructure have been determined. Gallingtests have also been performed on many commercially produced low- cobaltand cobalt-free alloy hardfacingsasmore » well as laser remelted AlloyNo. 156. 34 refs., 12 figs., 22 tabs.« less