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  • 1.  Finding High Purity Ni-Cr Suppliers

    Posted 07-10-2022 12:17
    Edited by Ho Lun Chan 07-10-2022 12:18
    Dear Community, 

    I am writing to see if there are any recommended vendors that manufacture high purity (>99% ) Ni-Cr alloys? I am currently planning to use these materials for my thesis research project. I purchased a few Ni20Cr alloys from a commercial supplier (not disclosing the name) yet the alloys seem to contain separate Cr phase in the Ni-20Cr matrix, which I was not able to get rid of through heat treatment (the alloy is also not very pure). I attached the data below. 

    I am looking for relatively small quantality (100mm x 100mm x 3 mm plates for Ni5Cr, Ni10Cr, Ni20Cr, Ni30Cr). I have difficulty finding any commercial vendors for these materials. 

    Do you have any recommendations on suppliers? 

    Thank you very much for your time! 




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    Lun Chan
    Mentorship Chair, EPC Committee
    PhD Candidate, University of Virginia
    Charlottesville VA
    (323) 688-7872
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    Metkon USA - Technology behind Specimen


  • 2.  RE: Finding High Purity Ni-Cr Suppliers

    Posted 07-11-2022 18:58

    Ho Lun:

     

    I imagine that if all else fails you could prepare your own Ni-Cr alloys for your thesis work starting with high purity metals.  A long time ago I had to prepare the beta brass material needed for my MS thesis.  It was very educational!

     

    Nassos Lazaridis




    Metkon USA - Technology behind Specimen


  • 3.  RE: Finding High Purity Ni-Cr Suppliers

    Posted 07-12-2022 12:16
    You have to understand the thermochemistry of melting. Oxygen will be present in your raw materials, and more may be introduced by reaction with refractories. A small addition of deoxidizer may be needed at the end of melting to prevent formation of chromium oxides. Deoxidizers commonly used include aluminum, titanium and silicon. Silicon is not the best deoxidizer but the silica will react with alumina to make aluminosilicates that are more likely to agglomerate and float during solidification. Titanium also forms carbosulfides that may help remove some sulfur. If a high-lime (CaO) slag is involved, the aluminum will help to remove sulfur also via inclusion of CaS into the slag. If you want minimal oxide inclusions (there always will be a few), you will have to accept some residual amounts of the deoxidizer(s). Typical levels might be 0.01 Al, 0.04 Ti, and 0.20 Si.
    At one time, many research centers had small vacuum melters that produced alloys such as you described. You could contact them to see if they would be willing to do that for you. If not, there are many small melt shops that can make and sell you custom alloys. 

    --
    John Grubb



    Metkon USA - Technology behind Specimen


  • 4.  RE: Finding High Purity Ni-Cr Suppliers

    Posted 07-13-2022 06:42
    I agree with John - melting is a whole science in and of itself, and there are many variables, not only purity of the raw getting melted but what type of furnace, refractory, slag, pouring method, chronological order of alloying additions, etc. He is correct that deoxidation is typically performed via addition of some sort of "getter" element such as aluminum, titanium, etc., which is mostly removed in the slag but you will have some amount of inclusions left over.

    That said, here are two melting processes you might consider to achieve the level of purity you're after:

    A vacuum melting process such as VIM or VAR. The idea here is that, by pulling a vacuum on the melt, you can remove some of the gases that way. Often this is done two or three times until a point of diminishing returns is approached. This is a commercially available and well-established process, although if you're ordering a heat from a mill, there will be a minimum buy of at least several thousand pounds (vs. finding something off the shelf at a distributor that was melted this way to buy in the small quantity you're after).

    Electrolytic refining. This is not my area of expertise so I will defer to anyone else in the forum who may know more about it but often precious metals such as gold are purified via electrolysis; essentially you have them in solution and then electroplate them onto a cathode. I don't believe that you could electroplate out this specific 80/20 alloy you're looking for but you could use it as a method to get very pure nickel and chromium independently (or buy said pure metals from someone else who has used this process) and then melt them together in a vacuum furnace to get your alloy.

    I'm not aware of what companies out there are performing these processes on a small scale but the big name manufacturers of nickel alloys that come to mind are SMC, Carpenter, Haynes, and ATI; you could contact representatives of those companies to see whether they have divisions that do small jobs like this but I'm sure that the price per pound will be exorbitant.

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    Sean Piper
    Product / Process Metallurgist
    Ellwood Texas Forge Houston
    Houston TX
    (713) 434-5138
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    Metkon USA - Technology behind Specimen