Study of cobalt-free, Fe-based alloy powder used for sealing surfaces of nuclear valves by laser cladding

To avoid the activated radiation of cobalt-based alloy, a new cobalt-free Fe-based alloy powder (FeCr-1) has been developed. In addition to the main constituent of Fe, this powder contains C, Ni, Cr, B, Si, W, V, Mo, Mn, etc. By using a hollow laser, FeCr-1 has been successfully prepared on the surface of stainless steel as the cobalt-free strengthening layer. Investigation reveals that the microhardness of this laser cladding coating corresponds to that of cobalt-based alloy Stellite 6. The XRD result reveals that the primary phases of, Fe2SiV, Ni2Si and Si2.2Mn6 as well as various fine carbides such as Fe0.4Mn3.6C, Fe3C and Fe5C2 exist in the coating. Analysis indicates that this kind of alloy has some advantages of high wear resistance, good corrosion resistance and high temperature tolerance. The capability of the Co-free FeCr-1 alloy powder is close to that of Stellite 6, thus it could be the promising candidate material of bead welding used for the new generation nuclear power valves.