The design of cobalt-free, nickel-based alloy powder (Ni-3) used for sealing surfaces of nuclear power valves and its structure of laser cladding coating

To meet the demand of cobalt-free for the cladding coating materials used on sealing surface of nuclear power valves, a new Co-free, Ni–Cr based alloy powder (Ni-3) has been developed. It has been successfully coated on the surface of stainless steel as the strengthening layer. The XRD result reveals that the primary phase of cladding coating is Ni-based solid solution, and the carbides M7C3 and M23C6 as well as several A3B types of γ′ strengthening phases. It indicates that the alloy possesses the high wear resistance, good corrosion resistance and high temperature tolerance. The test results suggest that the micro-hardness of Ni-3 corresponds to that of alloy Stellite 6 which containing cobalt and currently used as material for nuclear power valves. Hence, the developed Ni-3 alloy powder can be the hopeful candidate material for Co-free cladding material used on the surface of nuclear power valves; it can reduce the nuclear pollution and save the expensive metals.

Research highlights
► The Ni-3 Co-free alloy coating prepared by laser welding.
► Ni-3 alloy has excellent combination with stainless steel base.
► Ni-3 alloy containing those strengthening phases could have excellent wear resistance and anti-oxidation ability at high temperature.