High temperature wear and corrosion resistance of Co-free Ni-based alloy coatings on nuclear valve sealing surfaces

As a further step in obtaining high temperature wear and corrosion performances of a newly designed and laser cladded cobalt-free, nickel-based alloy coating (Ni-3) used for sealing surfaces of nuclear power valves, high temperature dry sliding wear behavior was characterized on a HT-1000 ball-on-disk tribometer at 360 °C, the hot corrosion test was conducted by plating Na2SO4 + K2SO4 mixed salt solution on the coating at 350 °C for 140 h. For comparison, the high temperature wear and corrosion resistance of the laser cladded Co-based Stellite06 and Fe-based Norem02 coatings were also investigated at the same testing conditions. It is found that the microhardness of the Ni-3 coating is about HV500 and close to Stellite06, but less than Norem02, the high temperature wear volume loss of Ni-3 coating is half of Norem02 and close to Stellite06. While during 350 °C hot corrosion test, the mass loss of Norem02 coating is the largest, Ni-3 coating is placed in the middle, Stellite06 coating shows the best hot corrosion resistance. Thus, the newly designed and laser cladded Ni-3 alloy coating appears to be the viable alternative material and technique for Co-free alloy, especially used in the nuclear valve sealing surfaces.