Plasma powder spray coating or plasma sputtering? Tungsten Carbide

A. Chris:

There's no way you can plasma spray such a thin layer without leaving an enormous amount of voids or bare substrate (probably up to 50%). The thickness you are looking for is within the range of size of the plasma powder particles! I don't know enough about the sputtering.

A. ZrN at the thickness you are looking for is typically deposited by cathodic arc, though you can sputter the coating on as well. Arc deposition is just easier, as the cleaning of the substrates is much less important (high ionization of the zirconium). A number of companies can do the work for you, if your batch is large enough to cover a full run.

A. Yves, "carbide" is usually short for "cemented carbide", which is a name for a mixture of a metal carbide particulate held together in a cobalt (or less commonly another metal) binder. The metal carbide is most often tungsten carbide, but chromium, titanium, and others can be found commercially. In this context, "carbide" is a "cermet", which merely means a mixture of ceramic and metal. It is certainly possible to have a cermet that isn't carbide- say, aluminum oxide mixed with aluminum would be a cermet, but not a carbide. (It's also pretty uncommon.)

Tungsten carbide cermets are available as bulk products: it's easy to find ball bearings, cutting tools, and wear pads made of the stuff. It is also a common coating applied by plasma or HVOF thermal spray techniques, and those are just about always polished afterwards. If I wanted to determine if a piece was solid tungsten carbide or coated steel, I'd check the density. Tungsten carbide is HEAVY.

ASTM specifications covering carbides are found in ASTM Volume 02.05.

Hope this helps!

A. Dear Sir,

For Tungsten carbide Coating , 100 Microns is Ok for all applications after finishing. If it a severe application of wear n abrasion then we need to have coating of 300 microns.

Regards,

A. 0.010" WC-Co or WC-Co-Cr is a walk in the park on 4150, especially when applied via HVOF. The HCAT website has published wear data on these coatings at this thickness. 0.001" thermal spray thicknesses often present practical challenges with adhesion. Most tech bulletins for thermal sprays mandate a 0.003" minimum.

That said, application angle is vital to coating consistency with HVOF. anything less than 45 deg from the surface may present problems. An uncomplicated geometry might be more forgiving with a plasma applied coating, and will allow angles approaching 30 deg. when I hear this application, I think along Mr. Marrufo and Mr. Watts's path of non line of sight coatings. But chrome at 0.010" might yield corrosion issues on 4150 from micro-cracking, and certainly will wear faster. PVD rocks for this sort of stuff, (maybe a layered TiN/Ti?)great with cavitation, but it isn't always cheap. Definitely a batch process.

The cheap way I would go is an e-plate Sulfamate Ni base, with a Hard Cr top coat, but watch your embrittlement. Used on Landing Gear all the time. Corrosion/wear resistant, cheap, Non-LOS, repeatable.