Microstructure, wear resistance and electrochemical properties of spherical/non-spherical WC reinforced Inconel 625 superalloy by laser melting deposition

The strengthening mechanism of spherical WC and non-spherical WC reinforced Inconel 625 composite coatings was investigated by laser melting deposition technique. The microstructure, phase composition, wear resistance, and electrochemical corrosion performance of the 15 wt.% spherical WC/IN625 and 15 wt.% non-spherical WC/IN625 composites are studied. The addition of WC changes the grain growth of the coating, forming columnar grains perpendicular to the WC and fine equiaxed grains around the WC particles. WC is partially decomposed during laser melting deposition, where the non-spherical WC decomposes more seriously, and the C and W elements in WC diffuse into the IN625 matrix. The decomposed WC and other elements in the coating generated new phases such as WC, W2C, NbC, W6C2.54, and M23C6. The newly formed hard phase and the undecomposed WC particles are uniformly scattered in the IN625 matrix, which improves the microhardness, wear resistance and corrosion resistance of the substrate. Since non-spherical WC is more prone to breakage during the frictional wear phase, the wear resistance of the spherical WC/IN625 coating is stronger, with a wear rate 0.13 times higher than that of the non-spherical WC/IN625 coating. During electrochemical corrosion, the corrosion current density of the spherical WC/IN625 coating is 0.78 times higher than that of the non-spherical WC/IN625, and the polarization resistance is 1.18 times higher.