Diamond Coating of Tungsten Carbide

[engineer23]

Does anyone have any expertise in the coating of WC tools? Are these tools coated by a deposition process (ex. CVD)?

 

[darkelf]

WC (Hard tools) are good substrates for diamond coatings. The meet all the requirements for this sort of coatings. They are coated by a CVD process and loads of research has gone into this area.

Hot Filament CVD has been used. You can also look into the paper 'Interaction of hard metal substrates during diamond deposition' by R Haubner for more information.

 

[engineer23]

Most papers I have found focus on coating a base material of WC-Co. Is WC always alloyed with Cobalt? It is possible to have a tool that is WC alone?

It seems that the alloying is done to make the material less brittle (and thus avoid fracture of tools in machining applications). I also understand from these articles that the Cobalt binder inhibits adhesion of diamond to the substrate. One article recommended a course of chemical pre-treatment to remove the Cobalt binder from the substrate surface. While using WC would make the tool more brittle, wouldn't it also make it easier to coat?

 

[Astronuc]

WC-Co is a cermet. WC is very brittle, and the Co is basically a more ductile binder.

This paper might be of interest
http://www.matmod.com/Publications/armor_1.pdf

There are probably other good papers, but it's a matter of finding them.

 

[engineer23]

^Thank you. That paper is very helpful. I ordered some WC tools to be coated with diamond (in search of the ever-elusive wear resistant tooling). I'm guessing now that these are in fact WC-Co tools? That would explain the difficulty that the diamond lab has encountered in attempting to coat them using CVD tehcniques (this is their first foray into coating WC).

It seems like the surface pretreatment suggested in some of these papers to etch away the Co from the substrate surface may be a potential solution to our problem.