Case colour hardening

[BobH]

Is it possible to have a case colour hardened finish, similar to that found on firearms, on a straight razor blade?

If this is posted in the wrong forum mods feel free to move it.

Bob

[ejmolitor37]

Im no scientist but I would certainly think it would possible, I was looking into nitre bluing for a black powder pistol I have and that does not seem to invasive a technique. I don't remember how hot things get but with the gun parts just went into a bath of the nitre solution and once pulled out Bobs your uncle. (Not you of course ) I am very interested in what others have to say on this I love color case look!


Well I guess I should retract this statement about nitre bluing, I forgot that turns the metal a kind of purple rather than the brown hues of color case. Sorry about that, but the nitre color could also be attractive

[BobH]

IIRC there are cold and hot blue methods that produce a rich dark blue. there is also plum bluing and rust/brown bluing. It's been a long time since I was into firearms. I still use an old bottle of Hoppes cold blue for doing tangs and darkening deep etches. When I say old I mean the bottle is likely 30 years old.

Bob

[Geezer]

True color case is developed by heating to a red heat in a carbon rich environment and dumping the object into a water bath as would be done in hardening.
Not a good idea for a razor.
~Richard
PS. Wikipedia would be a good place to begin.

[JimmyHAD]

Going along with what Richard posted, I seem to remember reading about Colt case hardening their Single Action pistols and IIRC they would heat the frames with bone included in the mix somehow. One way or the other, the end result was a hard exterior, and a soft interior.

Perhaps, as Bob mentioned with the cold blue, there is a way to duplicate the appearance, without compromising the temper of the blade ?

[BobH]

Going along with what Richard posted, I seem to remember reading about Colt case hardening their Single Action pistols and IIRC they would heat the frames with bone included in the mix somehow. One way or the other, the end result was a hard exterior, and a soft interior.

Perhaps, as Bob mentioned with the cold blue, there is a way to duplicate the appearance, without compromising the temper of the blade ?

Yes, like on the Colt SAA pistols, various lever guns and a few single shot rifles. Yes, I recall bone was involved in the process and it did only surface harden the steel. Just wondering if that process could be inserted into the forging and heat treating of a blade. OTH I suppose some sort of exposure to chemical fumes could produce a patina similar in looks to the old case colour hardening.

Bob

[JimmyHAD]

I love the look of a case hardened frame. S&W used to do their hammer/triggers case colored, not sure if they still do.

[Geezer]

Jimmy is correct. Bone and a chemical are parts of the "Bull's-eye Mix." The process done with "pack case hardening" is able to achieve a depth of up to a sixteenth of an inch in depth. Sheffield would take a member's ticket in an instant for case hardening of a blade.
For colors by heat they start at about 400°F for Light gold and that is at tempering temperature for about 60Rc and other colors are hotter and could readily soften a blade.
Richard

[BobH]

That answers that then.

Bob

[JDM61]

Most case hardening is typically done on mild or, at best, medium carbon steel. The objective is to "carburize" the steel sufficiently to surface harden, but not close to the hardness levels required for a blade. Remember also that the "colors" are surface oxides. if you think abut the typical modern gun BARREL steel, it is something like 41XX steel which,when hardened for tactical tomahawk bits,etc, maybe can get into the mid 50 range.