nitrile cutless bearings

[Brent]

Hi there I am needing some input on researching what coating would work best with a nitrile cutless bearing that runs on a stainless marine prop shaft It currently has a ceramic coating on it (that is worn and needs to be resprayed). we could reapply a ceramic with our flame spray gun. We also have hvof at our shop, would a hvof coating work well in this environment and bearing type. Any input would be greatly appreciated

[Brent]

Well I have gathered some more info that I will add to see if anyone has any opinions on the matter. This is the advice I have been given in regards to using a HVOF applied coating. The Cutless Bearing requirement is for a smooth surface on the shaft so that water is held there between the rubber and shaft to reduce friction to zero in operation. To get a smooth surface on the shaft a HVOF coating is best with a highly bonded, dense and wear resistant coating produced after grinding. (The other coating processes would contain some porosity at the surface and roughness which would increase friction). Due to a chloride environment we propose a WC10Ni coating. The current coating is chrome oxide ceramic applied with flame spray not plasma. Is there less friction with a hvof wc coating or a ceramic?

[KevGarty]

I would have thought HVOF would be the best bet, it sounds like a similar application to hard chrome replacement.

60 Rc NiCrBSi ground and polished ? Or your WC/Ni that you mentioned would prob be good

[Brent]

I would have thought HVOF would be the best bet, it sounds like a similar application to hard chrome replacement.

60 Rc NiCrBSi ground and polished ? Or your WC/Ni that you mentioned would prob be good

Thanks that is my thinking also but I need to be able to say why a certain process applied coating in this application is better than another with data to back up my argument.