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Sample preparation of round specimen to reveal grain structure

Sample preparation of round specimen to reveal grain structure

Sample preparation of round specimen to reveal grain structure

(OP)
I want to reveal the grain structure on the curved surface of a tubular sample made of stainless steel (SS 304). In the usual sample preparation method to reveal the grain structure one needs to polish the sample flat first and then etch it. But, I want to reveal grain on a curved surface of my tubular specimen (please see attached sketch) without polishing it flat.

Can anyone suggest the appropriate sample preparation method for my application? Is electrolytic polishing suitable here?

RE: Sample preparation of round specimen to reveal grain structure

There was no attached sketch. You can have a surface polishing technique that is used for field metallographic examination (replicas). After using 600 grit a portable electropolisher is used along with electrolytic etching with 10% oxalic acid. Contact a materials lab or testing group that can do replication or field metallographic examination.

RE: Sample preparation of round specimen to reveal grain structure

So do not want to section it, or can't you?
A longitudinal section would let you examine this structure.

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P.E. Metallurgy, Plymouth Tube

RE: Sample preparation of round specimen to reveal grain structure

Do you have a scope that can build an image on the curved surface? If not, you will only be able to look at a small section of the surface, depending on the magnification and the diameter of the part.

RE: Sample preparation of round specimen to reveal grain structure

And on 304 what does the grain structure matter, it is fully austenitic.
If you are looking for carbides or twining then you likely need to do sections in order to get good enough images.

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P.E. Metallurgy, Plymouth Tube

RE: Sample preparation of round specimen to reveal grain structure

(OP)
All, thanks for your suggestions and comments. Below is the sketch (the attachment didn't go with the main post).



Actually, I'm doing tensile testing with tubular specimen both inside and outside of a Scanning Electron Microscope (SEM). SEM has higher depth of field, hence I'm expecting to see more curvature, compared to what is visible with an optical microscope at very high magnification.
Now, the reason I'm interested in seeing the grain on the curve surface is because in this way my test samples will be the same (almost) for the tests performed both inside and outside. To reveal the grain, if I polish the surface flat, this will change the cross-section of sample, and hence my inside and outside tests will not supplement each-other.

I think what I need is the sample preparation technique with the least amount of surface alteration. Off-course, I'll need to take out some material from the tube surface, but I need to keep it to minimum. Hence, I'm thinking about electropolishing.

Any suggestion is welcomed.

RE: Sample preparation of round specimen to reveal grain structure

Mechanical grinding with appropriate equipment (small grinding discs) could be enough.

With appropriate microscope does not matter the curvature to attach it and watch directly, without need of replicas.


RE: Sample preparation of round specimen to reveal grain structure

FarhanRahman
This sounds like a research project for a thesis?????

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