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I am an student of archaeology and on my final work I am working with mining hammers, on which metallography was used. But my supervisor want to use some kind of acid on the surface of the metal so it would be visible difference between parts witch higher amount of carbon in steel and in those that don’t have any or low amount. Is it even possible? Or if it would help, would it be visible just under microscope. Thans for any answers.

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    $\begingroup$ Steel and iron have different etch rates in different acids. Look up which ones. If you have a metallography lab around, they likely have several books with different etchant recipes. $\endgroup$
    – Jon Custer
    Commented Feb 17, 2022 at 14:15
  • $\begingroup$ @JonCuster Cool. I would've gone total apparative overkill and said you need to map the surface with XRD. ;) Crazy how used we get to just having equipment for 100s of k€. $\endgroup$
    – Karl
    Commented Feb 17, 2022 at 23:24
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    $\begingroup$ @Karl - or EBSD with Auger mapping on top. Don’t mess around… $\endgroup$
    – Jon Custer
    Commented Feb 18, 2022 at 1:22
  • $\begingroup$ Have a look at Damascus steel (en.wikipedia.org/wiki/Damascus_steel) and procedures of etching. $\endgroup$ Commented Feb 23, 2022 at 21:41

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By "metal" I assume you mean iron in some form. The most common economical method is combustion of a small sample; nearly all carbon in iron analysis is done with this method. There are other methods like non dispersive x-ray fluorescence in an election microscope, but it will be costly. Metallographic examination using, for example standard nital etch ( ethanol with little nitric acid), can show an experienced person a great deal about the steel/cast iron. But the general color would be relatively useless in determining the carbon content. Without some information regarding what "mining hammers" you are looking at, it would be difficult to guess what they are. For example, light and dark areas could indicate heat-treatment and have no connection with carbon content.

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    $\begingroup$ If you can spare a few grams of sample , commercial labs will offer a package deal on 6 or 7 standard element analysis on steel. I don't know the price of a good deal today . It will include C,S,P, Si, Mn, Cr, Ni, Mo, maybe Cu. Results can be helpful for evaluating the steel. I am not sure about cast iron. If you can't spare material, a university should have a scanning electro microscope with EDAX , probably in physics department ; of course I have no clue about access. ( Every one should have an SEM with EDAX, they are impressive.) $\endgroup$ Commented Feb 17, 2022 at 17:43
  • $\begingroup$ Yes, I know, we have already use an election microscope, but I am trying to find other methods that would be visible be human eyes, cause we have already spent lot of money on election microscope and results are really weir and not really meaningful. The point of my work is to find out the most preferable method medieval smiths, have taken care of the working parts of the hammers. So when it would be visible just by human eyes it would be best for me, cause I would be able to do this on more examples and it would not be so expensive as election microscope. $\endgroup$ Commented Feb 17, 2022 at 18:56
  • $\begingroup$ It sounds like you need a metallurgist. The nature of inclusions ( silicates, oxides, sulfides) will tell a lot about the fabrication. The carbon can be completely changed by heat-treatment so it masks fabrication. Carbon could indicate if a "Damascus" type process was used. A light microscope with modest magnifications such as 40 to 100X will be most informative. I am thinking of a traditionally polished sample , unetched , then etched with 2% nital., also that it is a steel rather than cast iron. $\endgroup$ Commented Feb 18, 2022 at 23:48

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