I have two questions please,
- I have Nanostructured powder composition of WC-Co, I would like to do a cross section to get SEM image inside the powder, I tried cold and hot mounting and then ground and polished, but the results was that the powder been removed due to grinding!! does any one knows how to do the cross section for powders?
- Is there any chemical composition used as etching for thermal spray coating to show the microstructure clearly under microscope/SEM?
Thanks
Agree. Use FIB and high resolution SEM.
With regard to the second question. Use murakami reagent. See
http://www.metkon.com/en/application_etching_13.html
Normally you would spray the power to form a solid and then do microstructure. However your question seems to indicate that you want to look at the metallurgy of the powder before applying heat during spraying. If this is the case then use a strip of nickel as a substrate to place the powder on, then carefully immerse it in a solution of electrolysis nickel and plate nickel on the substrate and the powder. This should consolidate and bond the powder such that it can be sectioned, mounted and polished for etching, then studied in the SEM. Do the grinding and polishing as if it were ceramic, Buehler Diamet system. If your powder is very small, you will need about 40,000 x magnification.
For etching go to the books by either Kehl or VanderVoort for etching solutions and procedures.
Note the above technique must be done carefully as heating the electrolysis solution too vigorously will disturb the powder, do it by heating slowly until the powder is securely bonded onto the substrate, then raise the temperature to thicken the nickel coating.
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