Posted by Gordon England (62.252.0.12) on 13:53:16 05/06/06
In Reply to: etchants for ni-cr and wc-co posted by rambabu
Hi rambabu
I assume these are thermal spray coatings. Generally most thermal
spray coatings are view in the as-polished condition only. Etching
coatings can be difficult and the results can be uneven and
inconsistent. Substrate material very often interferes.
For WC/Co and WC/CoCr type coatings though, a useful etchant is
Murakami's, which I modify by diluting heavily as it tends to
be very aggressive. This is not a pretty etch, but it can indicate
the extent of oxidation and formation of metastable phases which
are not normally desired. At best you should see no etching.
NiCr alloy coatings I have not etch before, so all I can say is
experiment. The only thing I think that you will reveal over that
of viewing in the as-polished condition is the grain structure
within the splats.
Regards Gordon
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