Microstructure, corrosion behavior, and microhardness of plasma-sprayed W–Ni composite coatings

Commercial tungsten powder of average particle size 12 μm was mixed with 10 wt% Ni powder and plasma sprayed on a SUS304 stainless steel substrate. W–Ni composite coatings have been sprayed at different Ar plasma gas flow rates of 120, 150, and 170 l/min and different Ar carrier gas flow rates of 5, 8, and 10 l/min. The microstructure and phase structure of the sprayed coatings were investigated using a scanning electron microscope (SEM), X-ray diffraction (XRD), and an energy dispersive spectrometer (EDS). Corrosion tests were performed for the sprayed W–Ni coatings in a 3.5% NaCl solution using an electrochemical polarization method. It was found that the W–Ni coatings sprayed at a higher Ar gas flow rate showed higher corrosion resistance compared with coatings sprayed at a lower gas flow rate. A more positive value of the corrosion potential and a lower value of the corrosion current are observed for coatings sprayed at a higher Ar gas flow rate.