2micron WC coating on thin P-bronze disc

[drramc]

The two-micron thick coating of WC on P-bronze cutter disc is reported to have been done by electrophoresis process.
Coating material need not be WC but any material with similar hardness.
Resin impregnated SiC coating is common in grinding wheel manufacturing.
It may not be difficult to coat the surface with hard carbide plus resin, but how to get to 2-micron thickness limitation?
ram chattopadhyay

[Gordon]

Hi Ram

I suppose sourcing good quality nanometre sized particulates will be important.

Not sure if this link will be of interest

(link dead)

[drramc]

Hi Gordon,
You are right on finding nano-size carbide particles.But the nanos would be too costly for this application.
Since any powder above around 60 HRC would do, if I use some of the self-fluxing Ni-base alloys of (-)400 mesh,the thichness of single layer flattened deposit may not exceed 2 micron and then use epoxy as sealant.I am going to try this. I also would like to know if anyone has been able to get this thin deposit with these alloys.
ram chattopadhyay

[Gordon]

Hi Ram

Using thermal spray? I would have serious doubts about achieving lower than 2 microns using ~400 mesh powder. Even if every particle splatted out to slightly less than 2 microns thickness, you need to consider the somewhat random nature of particle trajectories at this level. Chances are you will have 3 particles pile up on top of one another in one area and nothing in an adjacent area, and not considering the possibility of a few large unmelts . I take it that you are concerned with getting a few particles in place rather than a continuous coating and that you are measuring thickness as peak thickness. I still think you will need to go much finer with particle size.

[drramc]

Hi Gordon,
You are right on the initial powder size.WC powder does not get flattened to the extent the other low melting point powder does.I am checking with some of the diamond tool matrix powder manufactureres, who specialise in making fine,below 1 micron powders of cobalt and other materials in different hardness range.
ram chattopadhyay

[Gordon]

Hi Ram

I suspect this will be a challenging project but then that makes it interesting.

You will probably experience a few problems with metallic powders at this size:

* Powder feeding particularly if using standard TSC equipment feeders.

* Avoiding excessive oxidation of powders during spraying.

Would alumina or chromium oxide ceramics be viable? I have plasma sprayed both at around the 1 micron particle size with some success (don't know about keeping thickness within the 2 microns though).