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-----Thin Hard-wearing Opaque coating for steel?
2000
Could anyone point me toward a coating which has the following properties (if this is possible). It is for a high-strength steel (approx. 55 HRc through-hardness), tempered at 300 degrees C (572 degrees F)
1. Low process temperature (to avoid softening the material)
2. Opaque (so that temper 'blueing' is covered)
3. Tough (or reasonably so, to avoid coating damage during handling and fitting)
4. Corrosion resistant
5. Thin as possible so as not to affect fit between adjacent parts. A coating which puts 5 microns on per surface has affected the fit between adjacent parts too much.
6. Non-electrolytic, either the coating process or preliminary processes. There is an obvious concern involving hydrogen embrittlement which we would like to eliminate
Am I being unreasonable in my wishes, or is this easily achievable? I would be very grateful for any recommendations that anyone could make.
Wayne Ward- England
You could look at some kind of Vapour Deposition. CVD, PVD. I don't think the parts are heated during that.
Ian Brookeuniversity - Glasgow, Scotland
2000
Ian's suggestion above makes sense. Some PVD processes could give you what you need. However, the type of coating depends on what you mean by corrosion resistance. Is it in-doors, out-doors, humid or marine environment, etc. For more severe conditions, you may need a combination of coatings.
Mandar Sunthankar- Fort Collins, Colorado
2000
As noted, PVD may be the right process, but it's very difficult to recommend any coating in the abstract; you always need all the details including sizes, shapes, production rates, etc. The only caution I would add is that electrolytic processes are not the only potential source of hydrogen embrittlement. Any acid pickling or activation that may be required (depending again on the real world situation) can introduce hydrogen embrittlement. Your criteria would necessitate an acid-free cleaning process--so you might need some kind of blasting or vapor honing.
Ted Mooney, P.E.
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2000
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