A review on application of nickel base hardfacing alloys in sodium-cooled fast reactor

An overview on processing, performance, and applications of Nickel base hardfacrng alloys in Sodium-cooled Fast Reactors (SFR) is presented in this review article. For many components in SFR, the need for superior wear-resistant matenal with reliable tribological properties is a prerequisite for ensuring the safety of the reactor. Hardfacrng of the base matenal is a common practice followed in nuclear industries for rmprovmg the wear resistance of structural components. Recently, Ni base hardfacrng alloys have drawn significant attention as a potential replacement of Co base hardfacrng alloys for nuclear reactor components. This is because cobalt base alloys are known for causing occupational radiation exposure in nuclear reactors. Nickel base hardfacrng alloys are deposited on the base alloy by various methods. Among them, laser cladding, Plasma Transfer Arc Welding (PTAW) and Gas Tungsten Arc Welding (GTAW) have generated interest owing to their high process efficiency and ability to produce superior hardfacrng overlays on the substrate matenal. However, the potential application of these processes is achieved only via proper control of process parameters and with minimum dilution from the base matenal. The wear performance of Ni base hardfacrng alloy mainly depends on its micro structural constituents. It has been reported that boride and carbide precipitates in Ni alloys impart excellent hardness and superior wear resistance at a wide range of temperatures. In this review article, the sliding wear behaviour of these alloys is reported at service temperature ranging from room temperature to 700 °C. The analysis of worn track and worn debris from the wear test of Ni alloys showed that abrasive and adhesive wear were dominant mechanisms at ambient temperature; whereas, at a higher temperature, adhesive wear was the dominant mechanism which was accompanied by the formation of oxide tnbo-layer. The formation of oxide tnbo-layer is known to play a major role in decreasing the coefficient of friction.