Microstructure and corrosion properties of laser cladding MoNi based alloy coatings

Mo-based alloys are widely used for their excellent wear and corrosion resistance as well as high temperature resistance. Mo-NiCrBSi and Mo-Ni alloy coatings were prepared on 1020 water wall tube by laser cladding technology in the present study. The microstructure and phase compositions were analyzed by means of the scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and X-ray diffractometry (XRD). The corrosion properties of the coatings were evaluated by an electrochemical experiment at room temperature in 3.5 wt.% NaCl electrolyte. With increasing content of Mo, the structure homogeneity in Mo-Ni coatings deteriorated, the grain size increased, the average hardness and the corrosion resistance declined, due to the more content of harmful phases. Compared to the Mo-Ni coatings, the overall performance was better for the Mo-NiCrBSi, which had the higher hardness contributed by the element B and Si as well as the better corrosion resistance due to the addition of Cr.