Tungsten Carbide Anti-corrosion Research (1/2)

Conventional tungsten carbide is composed of hard phase WC and the binder Co. Due to Co has good wettability on WC, tungsten carbide has high hardness, high density, high strength and excellent chemical stability, which can be widely used in some wear parts and cutting tools machining. But as binder, Co has poor anti-corrosion, especially for scour corrosion so that to add some other elements with good anti-corrosion or to find new binder becomes the new directions of related researchers. The principle of Co oxidation corrosion of WC and Co is formed of two electrodes in the electrochemical etching solution, to form a closed loop enclosing an electrolyte. WC as a catalyst to promote the electrolytic solution boundaries O₂, producing O^2-, forming a cathode; Co as the anode is oxidized and causes the corrosion.

The Common nickel (Ni) can effectively take place of the cohesive effect of cobalt (Co) and improve the anti-corrosion of tungsten carbide. But tungsten carbide hardness (HRA) affected its formation, as compared to the original cobalt tungsten carbide decreased 0.5-1 times, only 70-80% strength cobalt tungsten carbide, which is only suitable for less demand in strength, wear resistance situations. In addition, add chromium (Cr) in the binder is also a kind of common method to improve anti-corrosion of tungsten carbide. It can remarkably decrease the corrosion rate of tungsten carbide in corrosive conditions, refine tungsten carbide grains and strengthen the binder phase, which not only improve the anti-corrosion of tungsten carbide, but also promote other properties.