Author Topic: Color case hardening results (Read 3293 times)

David Rase · « **on:** February 28, 2020, 11:58:04 PM »

After many years of successfully color case hardening muzzleloading locks, breech plugs and tangs I ran into a stretch of less than desirable results over the past couple of months. Colors were dull, flat and gray. After several months of thinking about my process, rereading information and having discussions with friends I have come to a conclusion that switching to a carbon steel quench tank was the root of my problem. My first results were fine, then as rust started to build up on the sides of the tank, results became less than optimum.

My question to you scientific types is, could this buildup of iron oxide on the sides of my quench tank impact the quench results? It is the only variable that has changed in my process.

Pictured below are my latest results. I soaked the parts in a 2 to 1 ratio of wood to bone charcoal for 2 hours at 1400 degrees Fahrenheit and then reduced the temperature to 1375 degrees Fahrenheit for an hour then quenched in my plastic garbage can that was aerated using an aquarium pump.
David

Bob Roller · « **Reply #1 on:** February 29, 2020, 12:14:30 AM »

Absolutely beautiful colors.I also use a plastic 5 gallon can that pickles came packed in
with 5 gallons of distilled water and 2 pounds of potassium nitrate.No longer have a
fish tank aerator but do stir it with a wood rod before quenching.I still have a little
Kasenit and use it sparingly and am UNDERWHELMED by Brownell's and Cherry Red
compounds. Brownell's smells of strong ammonia and generates too much smoke in
my little shop.Neither gives me the colors I can sometimes get with the Kasenit.
They DO harden the material and I use them on the current run of Double Set triggers
I am making now.
Bob Roller

JPK · « **Reply #2 on:** February 29, 2020, 01:29:11 AM »

I would consider the water source, if it’s city water some places add chemicals at times.

Scota4570 · « **Reply #3 on:** February 29, 2020, 01:59:49 AM »

My question to you scientific types is, could this buildup of iron oxide on the sides of my quench tank impact the quench results?

I bet it would. The rust maybe causing the oxidation reaction balance to be off, making the colors skewed. If you have too much iron oxide already it may cause more reducing environment and less oxidation of the parts. A real chemist could explain it better.

Try quenching is a clean plastic bucket with distilled water as a baseline?

B.Barker · « **Reply #4 on:** February 29, 2020, 03:57:42 AM »

Really nice looking colors Dave. What kind of container do you pack your parts in?

Dennis Daigger · « **Reply #5 on:** February 29, 2020, 04:52:15 AM »

Beautiful, David and the colors are quite English/Continental.
Dennis

Carl Young · « **Reply #6 on:** February 29, 2020, 07:46:49 AM »

Hi David, i think you might find some clues in this patent application:

Colored razor blades are provided. Methods for manufacturing such blades are also provided, including methods involving subjecting a blade material to a hardening process; and, during the hardening process, oxidizing the blade material to form an oxide layer on the blade material. The method also includes quenching the blade material, after the oxidizing step, to initiate martensitic transformation of the blade material, and forming the hardened blade material into a razor blade, the oxide layer providing the razor blade with a colored surface. https://patents.google.com/patent/US7284461B2/en

Good luck and keep us posted.
Carl

Marcruger · « **Reply #7 on:** February 29, 2020, 01:59:27 PM »

That is some beautiful color case hardening David. Well done. CCH is a fascinating but fussy process. God bless, Marc

JCKelly · « **Reply #8 on:** March 06, 2020, 06:27:04 PM »

Yeah, I'd use a stainless tank or at least get the rust out of yours.
The very best (and only, that I know of) article on color hardening was a two-part series by Oscar L. Caddy, Winter 1996 and Spring 1997, The Double Gun Journal

The bone charcoal one uses "contains approximately 80 percent tri-calcium phosphate which dissolves readily in hot water which is produced in profusion near the surface of the hot steel during the quench."

This is the stuff that makes durable case colors

Send me a genuine email address (forgot to look under your profile) and I'll send you these articles

Bob Roller · « **Reply #9 on:** March 06, 2020, 06:40:19 PM »

The Double Gun Journal.Is it still alive and available? I used to buy it at
a local book shop but I haven't seen one for years..
Bob Roller

rtadams · « **Reply #10 on:** March 06, 2020, 10:04:19 PM »

3-6-20

--- YES ---

Best Regards.

Robert

Bob Roller · « **Reply #11 on:** March 06, 2020, 10:18:08 PM »

Quote from: JPK on February 29, 2020, 01:29:11 AM

I would consider the water source, if it’s city water some places add chemicals at times.

As my small boy once asked me "Dad,does water supposed to have moving parts"?

My wife can NOT drink the water here in Huntington WV and we buy bottled water from
Kroger.
Bob Roller

Daryl · « **Reply #12 on:** March 07, 2020, 08:39:35 AM »

The blues subdued, but very pleasing to the eye, David R.

Blue on every piece. Well done. (but not quite perfectly centered on the top jaw.)

STJ1954 · « **Reply #13 on:** March 07, 2020, 02:46:44 PM »

For a number of years I did the cyanide case hardening. I had pot furnace that would heat to 1500. I had a wood tank that was aerated. The quench water was a nitrated mix I purchase from a vendor. Can't remember the name. This was the same system that Savage Firearms used. I had great colors more blues that browns. Very dangerous, got rid of this about 20 years ago. I tried a little bone charcoal but never has much success. The key to the colors seems to be with the nitrate mix in the quench.

STJ1954 · « **Reply #14 on:** March 07, 2020, 03:01:59 PM »

Forgot to mention I used distilled water!

Eric Kettenburg · « **Reply #15 on:** March 07, 2020, 04:17:44 PM »

Dave those colors are fantastic. I don't do much of that any more since most of the time I'd just be rusting and rubbing it off anyway (

) but I was typically able to get lots of colors and lots of blue by dumping a good slug of saltpeter into the quench.

I read something interesting, sometime, somewhere, about an interaction in the quench of salt crystals (from the saltpeter) trying to form on the surface of the hot metal as the water comes into contact with it and is momentarily vaporized, and the salt crystals exploding - I'm not explaining this well because I can't really remember the entire thing. I imagine it was all occurring at a microscopic level.

Dennis Daigger · « **Reply #16 on:** March 08, 2020, 01:13:36 AM »

The lock is finished and assembled. I'm pretty happy with it.

Eric Kettenburg · « **Reply #17 on:** March 08, 2020, 01:58:40 AM »

Yep, looks spectacular imho.

jerrywh · « **Reply #18 on:** March 08, 2020, 04:00:29 AM »

Yep that is great. Dave Race is about as good as any body I have ever seen and way better than most.
The above mentioned article in dbl, gun digest is the best article on case hardening I ever read but there are many small complications that can occur that no article will tell you about when it comes to color case hardening and no body will tell you about them. Among them is quench temperature quench oxygen content, steel alloy content, quench impurities. quench temp of the parts, distance from the quench to the pack when dumped. Heat stability of the pack. You can have good success for a period of time and all of a sudden everything goes haywire. Dave can testify to some of these I'm sure.
I do not recommend using potassium nitrate in the water. I can intensify the blues but usually it results in all blue or nearly so. Below is an example of using a couple of table spoons full of potassium nitrate in the quench.

Daryl · « **Reply #19 on:** March 08, 2020, 04:53:02 AM »

I expect much would depend on volume of the quench container as well.

jerrywh · « **Reply #20 on:** March 08, 2020, 09:04:08 AM »

The volume of the quench for that lock was 5 gallons.Temp about 55°F Part quenched at 1350F

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Author Topic: Color case hardening results (Read 3293 times)