The substrate material I have used to deposit the coatings is a Tungsten carbide tool insert. I have 2 coating variations: one with a monolayer of TiAlSiN and another with a bilayer of AlTiN/TiAlSiN. Each coating lies in the thickness range of 3-4 micrometers and has been deposited throughout the insert using PVD magnetron sputtering. I want to verify the coating thickness and with that study the microstructure at the cross-section. Previously when I used wire EDM to cut the monolayer insert, I observed a sort of coating folding/buckling, and could not get a precise reading on the thickness of the coating. After polishing the same, I wasn't even able to see the coating properly at the cross-section in the SEM. I have been thinking of using the method of brittle fracture combined with wire EDM. The insert will be cut up to 90% of the cross-section using wire EDM and brittle fractured after. This way, the fractured side can be polished and viewed under SEM. Is this method viable or are there any other better suggestions? If in case this method is viable, any suggestions on which method to use to brittle fracture the sample?
Dear Sriram
If you are going to fracture the sample, there is no need to polish afterwards. you may observe the coating fractured cross-section view in FESEM.
You could also deposit the coatings on a glass substrate (like cover glass), then examine cross-sections after breaking the glass.
Dear Sriram Chembai Ganesh ;
Sure you can use a wire-cut electric discharge machine without polishing to make your fracture toughness test and coating thickness measurement for the scross-section view of the FESEM samples images. more details in the following reference;
http://kth.diva-portal.org/smash/get/diva2:790051/FULLTEXT01
Dear Shayan Sarraf and Mahmood H. M.;
Thank you for the answers. I was able to view the coating thickness and subsequently the coating microstructure at the cross-section through using a mix of wire EDM and brittle fracturing. The insert was cut up to 90% of its cross-section through wire EDM and then dipped in liquid nitrogen for a brief interval before brittle fracturing. The insert was then cleaned and viewed under FESEM.
it may be put in the pattern and fill with epoxy, and then it can be machined with cutting, followed by a polishing procedure
I also suggest focused ion beam (FIB) if you have in your lab. It would give you the possibility to choose the exact area that you want to see with less effect on your film.
You may also consider buying WC-Co sheet substrates for your future work. you can easily break them and are good for lab research on such targets.
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