I have welded two 6mm thickness stainless steel 304L plates in butt joint configuration by TIG welding and I want to prepare a specimen for macro structure study. What are the different cutting methods I can use to obtain the specimen without having any or less effect on the macro structure profile? Can I go for wire cutting method or please suggest some other feasible methods.
What do you mean with macro structure study?
In general you have to select a technique where you are sure that you do not have and impact from the cutting. You can use everything as long as it does not influence your observation.
Macro sounds quite rough so that I assume you can use a standard metallographic cutting machine, but also a wire. It takes longer, and you prevent any deep damaging. However, you need to prepare your surface anyway so that I woud not do this. Then it is better to invest the saved time for the final sample prep.
Everything depends how good is your weld and what is the geometry of whole sample. If you have quite small sample use EDM. If you have large sample use handheld saw for rough cutting and EDM for precise cut. Before cutting be sure that everything is mounted as stiff as possible and will not bend during cutting. If the angle of the joint is 90 degree you can also place it on square pipe and cut it together with profile. This should also prevent your sample from deformation.
Just to let you know often when people or welding related articles mention macrostructure study, they usually mean examining the whole weld transverse cross section so including the weld width, penetration and other features such as undercut, reinforcement and etc., so around 1-10x magnification, rather than looking at the microstructure at higher magnification.
What do you suggest Michael to examine residual stress using a cutting method. Is there any other good way of doing it other than edm for contour method?
We investigated many years ago the impact of EDM on the residual stress measured with XRD (sin²psi). We found out that during EDM a non-neglectable amount of carbon is implemented in the surface-near area and therefore stress which is not related to the bulk. Therefore, one has to remove several hundreds microns e.g. by electropolishing.
@ Michael: you are certainly correct if you have mechanical damaging in mind, but see the above comment. However, it might be possible that over the years EDM has been optimized so that is does not introduce that much strain anymore.
On the other hand, since we use EBSD and there you would see immediately any kind of damage in a resolution which is much more critical compared to XRD, I would assume that a careful cutting, grinding and polishing is absolutely sufficient. The remaining errors are very likely of lower order compared to the errors resulting from the sample mounting, peak maximum positioning, and possibly also Young moduli used from other materials. In other words, if you are preparing half that good as required for EBSD everything should be fine.
EDM will be the best option but maybe a bit expensive if you don't have your own machine. prection cutting also may works but that will depends on your samples size. In general as long as you have cooling liquid the microstructure will not be effected.
Thanks
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