I would avoid laser cutting. Mechanical cutting plus polishing ("sandpapering"), but good polishing, to near mirror quality (you can find protocols on the Web). Of course, Brinell and Rockwell are out of question if you want to measure hardness in the immediate proximity of a coating. Vickers and Knoop microhardness tests may be useful, with Knoop working better for smaller regions.

As for EDS, beware of quantification of lighter elements, without proper understanding of technique it will be usually useless and misleading. Qualitative EDS analysis is a better option in most cases.

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I would avoid laser cutting. Mechanical cutting plus polishing ("sandpapering"), but good polishing, to near mirror quality (you can find protocols on the Web). Of course, Brinell and Rockwell are out of question if you want to measure hardness in the immediate proximity of a coating. Vickers and Knoop microhardness tests may be useful, with Knoop working better for smaller regions.

As for EDS, beware of quantification of lighter elements, without proper understanding of technique it will be usually useless and misleading. Qualitative EDS analysis is a better option in most cases.

I agree with Mr Dusevich if you just have a typical laser cutter because here you are locally melting up the material and by this you would cause alloy formation at the cutting interface and this will alter the results you obtain from EDS/EDX.

Doing a classical metallography procedure would also be my methode of choice, embedding the screw/ nuts in cold curing resin, cut it in cross-section and polish the scratches of with a polishing machine till the surface is shiny.

Regarding the EDS/EDX analysis: What do you want to find out? My recommendation would be to perform an elemental mapping. By this you will see the local elemental distribution in your area of interest (coating+ substrate interface). By doing so, you get a qualitative impression about the coating, the substrate and their interface. If you need quantitative elemental data, this will be more tricky.

Best regards,

Abdelkader Dehbi Vladimir Dusevich Mark-Daniel Gerngross thank you for your illuminating answers. it seems best way is mechnical cutting

Simply cut with precision diamond saw and follow standard metallography specimen preparation procedure to obtain mirror like cross-section. After that you can go with any measurement technique. Use Vickers hardness tester for measurement of base metal. For measurement close to coating use Knoop indentor as informed by @Vladimir.