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Coating alloys on rough sapphire substrates

We'd like to coat alloys such as Aluminum 6061, Copper 14400 and Steel 1045 on small sapphire discs with rough surfaces (Ra values from 0.1 micrometers to 5 micrometers - 4 microinches to 200 microinches). These surfaces will be used in calibration experiements.

Our requirements are that the coating be homogeneous, of the same composition as the alloy, and provides a continuous coverage on the surface being coated, without any gaps. The adhesion needs to be good enough for the coating to not peel off when heated to 200 degrees C. We do not care about other aspects such as stress in the coating, the temperature at which the coating is produced, etc.

We'd like to find vendors who can produce these coatings for us. We'd like to get about 10 sapphire discs of different roughnesses coated with each of the three materials listed above. Each disc is about 12mm in diameter and 2mm thick and only the top surface needs to be coated. Assuming that surfaces of different roughnesses can be coated in one batch, we'll need three batches of 10 discs coated, one for each type of material. We would also like to hear about techniques that can be used for these coatings, potential problems, etc.

Vis Madhavan
Wichita State University - Wichita, Kansas
2005

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2005

That doesn't sound easy by any techinique I know of., but some might exist. Have you considered ion-beam sputter-deposition? I think the compositional fidelity can be a few times better than regular sputter-deposition because it can have 10 times less gas pressure in the deposition chamber, so there's less atomic-weight-dependent scattering loss.

Otherwise, there's plasma spray-gun from wire-stock, maybe some other application of melted droplets, explosive lamination of sheet, arc-evaporation from wire, possibly self-sputtering of some metals from sheet-stock.

Hope you find a way.

James Swenson
- Los Angeles, California, USA