Laser cladding and wear testing of nickel base hardfacing materials influence of process parameters

International audienceIn 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 $^{59}$Co, stable, can be transmuted into $^{60}$Co 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.Previous presentations have shown the potential interest of some nickel base materials as Colmonoy alloy (Colmonoy 52 for laser cladding). In parallel, laser cladding has been identified as a deposition process that could increase the performances of the hardfacing materials compared to the standard process (Plasma Transferred Arc Welding). In all the study, the base material is the stainless steel 316LN. In the article, we sump up the previous results related to the investigations on these alloys. Then, another alloy is presented the Tribaloy 700 and evaluated. This nickel base has a complete different microstructure and its tribological behavior related to the variation of the microstructure is not well known. First, we present the selected materials. Then, we present the process parameter search. The quality of the clad is considered and the process window providing a good clad is determined (no crack, only few porosities,). The variation of the microstructure is analyzed and solidification paths are proposed regarding the process parameters.In parallel, a model of the laser cladding process is discussed and implemented under COMSOL software. Finally a simulation is presented and compared to the real clad.Finally, wear tests are shown on typical wear conditions. The movement is linear. Argon is used for protection of the sample against oxidation. Tests are made at 200°C. Wear tests are analyzed and interpreted against the microstructure of the material