Cobalt leaching of cemented tungsten carbide

[pip]

What can cause the selective depletion of the cobalt binder from a cemented tugsten carbide tool? The tool is used for drawing and operates in an aqueous environment pH 8.5 - 9.2.

 

Hi I have done some work on this question and thier is no easy answer. Basicly the type of amine used in the fluid is the biggest culprit with the fatty acid corrsion inhibitor 2nd then a cobalt inhibitor must be used also if not leaching will take place to. Example a correctly formulated fluid will not leach but 1-5 ppm of cobalt where a "normal" grinding fluid may leach 400-500 ppm over the same test period.
Good Luck

 

[hank]

I have seen cobalt leaching from carbide tools in alkaline environments (high pH). Your pH does not seem excessively high, so I would suspect that other factors might be at play. Is there any possibility of current through the tool? Alkaline conditions and DC current flow through the tool into the solution would definitely cause your problem. How do know that the problem is cobalt leaching, if I may ask.