Case Hardening a high carbon steel?

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by Vincent Price, Apr 5, 2020.

  1. Vincent Price

    Vincent Price

    39
    Feb 28, 2020
    I am new to forging but made knives via stock removal back in my twenties. I built a Forge over the winter and plan to boost retirement with a few hand forged knives here and there. My first customer who happens to be a friend wants a Bushcraft knife but wants it case hardened. He has a thing for the case hardened look and I have to admit being a "Cowboy" myself I do also. My question is can you case harden a high carbon steel like 1075 to achieve the color he's looking for? I say 1075 because thats what I have on hand and have used mostly. Would it be less durable as a knife? I have never case hardened anything. I know they make case harden coloring treatments you can apply but he really doesnt like that idea.
     
  2. Bill DeShivs

    Bill DeShivs KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Jun 6, 2000
    Case hardening is for low carbon alloys that need surface hardness. The temperatures involved would make high carbon steels very brittle.
     
    milkbaby and 12345678910 like this.
  3. N.W. Gean

    N.W. Gean

    120
    Oct 10, 2018
    I'm no expert on hamon or pattern welded steel, but it kind of sounds like that's what's being asked about.
     
  4. 12345678910

    12345678910

    Jul 13, 2009
  5. Vincent Price

    Vincent Price

    39
    Feb 28, 2020
    Yep, the guy wanting me to forge the knife for him wants the color case hardened color like the receiver of the rifle in the picture but on a 1075 steel.
     
  6. A.McPherson

    A.McPherson KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Jan 27, 2012
    You basically pack the parts in a mix of charcoal and bone, bake it at 1400f for an hour or so, then quench in water. Then oil be it up and leave it. You can't temper it or it'll ruin the colors.

    Like @Bill DeShivs said, it'll make a really brittle knife if made out of high carbon steel, and if you use mild steel, it'll make a crappy knife that won't hold an edge.

    You could case harden the furniture (guards, butt caps, etc).
     
  7. Ken H>

    Ken H>

    Dec 31, 2011
    Since he's wanting just the colors you could make the knife as normal (HT'd, tempered, etc) then polish the portion of blade you want the colors on to a nice mirror finish. Now with edge in water, use a hand torch to heat the rest of blade with hand torch to bring out colors. You can get nice blues, yellowish, etc with heat. That will make somewhat of a "case hardened" look. The colors are pretty sensitive and will be damaged pretty easy, so it's more of a "display" knife.
     
    milkbaby likes this.
  8. milkbaby

    milkbaby

    640
    Aug 1, 2016
    What @Ken H> said... torch temper part of the spine to give the colors he wants but keep the edge cool so you don't ruin the HT/temper of the cutting edge. But those colors are still only on the surface and won't last on a real user knife.
     
  9. JTknives

    JTknives Blade Heat Treating www.jarodtodd.com Knifemaker / Craftsman / Service Provider

    Jun 11, 2006
    Yeah heat temper colors just about wipe off with your fingers. That are not durable at all. Only color I have found that kinda holds up is that whispy blue colors from cutting a foil high temp open during heat treat of high temp steels.
     
  10. JTknives

    JTknives Blade Heat Treating www.jarodtodd.com Knifemaker / Craftsman / Service Provider

    Jun 11, 2006
    Maybe just make the blade from mild steel and case harden it. It would or should only be for display anyway if he is wanting those colors.
     
  11. coldsteelburns

    coldsteelburns

    Aug 2, 2010
    Maybe he would be open to using mild steel bolsters on his knife so you can case harden those. I've seen a few smiths do it on their guards and maybe butt caps. From what I've heard/read over the years, there seems to be quite a bit of trial an error and quite a few factors (some subtle and some not so subtle) in pretty much every step of the process that can affect how the color turns out, and even some luck, so you may have do it a few times to get something you like.

    ~Paul
    My Youtube Channel
    ... (Some older vids of some of the older knives I made)
     
    Last edited: Apr 7, 2020
  12. coldsteelburns

    coldsteelburns

    Aug 2, 2010
    I almost forgot, a bladesmith I follow on youtube just shared a video on his case hardening process a few days ago while doing some fittings. Maybe it could be of some help to you if you happen to end up trying it out.




    ~Paul
    My Youtube Channel
    ... (Some older vids of some of the older knives I made)
     
  13. coldsteelburns

    coldsteelburns

    Aug 2, 2010
    As others have mentioned, some air hardening steels (D2, A2, etc) are able to get some pretty colors. I don't know how much they hold up on his knives, but I've always though Medford's was able to get some pretty neat colors with his "Vulcan finish" (oxides from heat treating left on the blade). He may do something else to the blades to help influence the colors, like purposefully allowing some oxygen to remain in foil packet (for heat treating) or maybe putting some oil on it, but I dunno.

    Anyway, from a purely aesthetic point, I think the colors on ones like these look very nice:

    https://www.instagram.com/p/pcJysaMXaU/

    https://www.instagram.com/p/lkP6PwMXcT/

    ~Paul
    My Youtube Channel
    ... (Some older vids of some of the older knives I made)
     
  14. coldsteelburns

    coldsteelburns

    Aug 2, 2010
    Here's a recent little kiridashi I made for myself to try out some heat coloring on (with a plumbers torch). I wanted to see if the rougher surface from forged finish and/or the "ura" (hollow, fuller) on the back would help to hold the color a little better over time, although the oxides aren't on the actual blade, so the only wear it'll get will mostly be from handling it.

    [​IMG]


    [​IMG]

    (Those two spots with the vibrant purples on the back are actually peacock blues, but in certain lighting and angles they look like the above)

    But yea, just wanted to show some example of the ways already mentioned above to achieve some colorful oxides.

    Ok, now I'm done... lol
    ~Paul
    My Youtube Channel
    ... (Some older vids of some of the older knives I made)
     
  15. Vincent Price

    Vincent Price

    39
    Feb 28, 2020
    Thanks everyone.
     
    coldsteelburns likes this.
  16. Hankins

    Hankins KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Dec 7, 2008
    What might last is leaving the flats rough Hot Rolled 1075 doing the grind HT etc... Then edge in water and Heat color the spine using Map gas in a torch. This way if it gets used the rough parts will retain the color better
    Good coat of Ren Wax will help: https://www.texasknife.com/vcom/product_info.php?products_id=2028
     

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