Influence of W content on microstructure and corrosion behavior of laser cladded Inconel 718 coating

The microstructure and corrosion behavior of Inconel 718-xW (x = 0, 6, 12, and 18 wt%) coating was investigated. The results reveal that W addition can inhibit the formation of interdendritic, refine the grain size, promote the formation of Laves phase, and even form the Fe2W phase inside the Inconel 718-18W coating. The Inconel 718-6W coating demonstrates excellent corrosion resistance in 3.5 wt% NaCl solution with low corrosion current density, and high potential, and its polarization resistance is 11.99 times higher than that of the Inconel 718 coating. W element is able to promote production of more oxides and hydroxides on the surface of the coating by other elements, significantly enhancing the denseness and stability of the passive film. While excessive addition of W leads to a reduction in the corrosion resistance of the coatings, due to the increase in negative galvanic effect caused by the large number of Laves and Fe2W phases generated within the coatings. In addition, the geometrically necessary dislocations inside the coatings increase with the rise of W content, which can destroy the integrity of the passive film, adversely affecting the corrosion resistance.