Contribution to the replacement of cobalt-free hardfacing coating by laser cladding in fast neutron reactors

In fast neutron reactors, some parts can be submitted to displacements between each other (as movable parts for example). On these parts, the contact areas usually need a hardfacing coating. The standard hardfacing alloy is a cobalt-base alloy (as, for example Stellite®6). Unfortunately, in the primary coolant circuit and on wear conditions, cobalt can be released. Under neutron flux, the 59Co, stable, can be transmuted into 60Co by radioactive capture of neutrons and, therefore, can contaminate the primary circuit. Therefore, it is desired to replace this cobalt based hardfacing alloy by a cobalt-free one.First we sum up the existing results on cobalt-free hardfacing materials. Several types of materials such as nickel-base alloys, iron-base alloys and ceramics own interesting properties. However, it has been evidenced that there are few and incomplete works that attempt to understand the links between the material composition, the microstructure of the material obtained by the deposition process and its...