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Old April 06, 2018, 12:04   #1
Nathaniel01
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Nitride Questions

I had a gunsmith nitride a firearm and I really like the finish.
There is a local company that does nitriding, various methods.

What temperature range is safe for the firearm parts, small springs removed of course. Anyone have any tips?

http://ionic-tech.com/
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Old April 07, 2018, 09:59   #2
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One advantage of nitriding is that it requires relatively low temps so doesn't generally affect core hardness. But it's a case hardening process so that might assume one isn't performing it on a part that is already hardened (an FAL locking shoulder, for example). It's very commonly applied to barrels, bolts, and receivers. So unless you have a specific part in mind I'd say it's safe for almost all parts except springs and maybe hardened parts like locking shoulder. I don't know if it would harm a locking shoulder but I don't see how it would improve it. If you are looking for a cosmetic/corrosion/wear coating for a hard part the DLC may be better choice (though it adds thickness).

Speaking on springs, cryogenic treatment does extend spring life significantly. But most firearm spring are cheap and easy to replace. High performance springs such as valve spring are commonly cryogenically treated to extend life and reliability.

I know a little about this stuff but I AM NOT AN EXPERT.
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Old April 07, 2018, 22:11   #3
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gas or ion nitride? We have parts nitrided daily and have switched strictly to ion. With gas nitride we were getting about .008" case depth. With the ion nitride we can get up to .020" but it`s a 36hr process. The ion treated parts seem to hold their dimensions WAY better than the gas nitrided parts too. This is all on 4140. Our nitride shop has been doing some stainless steels (300/400 series and 17-4ph) but can only get about .003" case on them.

We use it for wear resistance, but it does add a little corrosion resistance.
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Old April 12, 2018, 10:14   #4
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The company offers many nitriding services, but they say the temperature for gas is 925-1050 F and the ion is 850-1100 degrees F.

I thought it would be a neat and easy way to get a nice finish with improved wear and corrosion resistance. The FAL I had nitrided was sent off somewhere by Jeff at Hillbilly Firearms, and looks great.

I was quoted a price of 50lbs of material for about $150. I paid about that much for the one rifle to get done.

Will this process burn off all the paint, or does it need to be stripped beforehand?
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Old April 13, 2018, 18:48   #5
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Do NOT nitride the threads!
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Old April 16, 2018, 06:59   #6
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Which threads should not be nitrided?
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Old April 16, 2018, 08:12   #7
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Right hand or left-hand threads.
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Old April 16, 2018, 22:14   #8
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So how do you not Nitride threads, presumably it's an immersion process?
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Old April 17, 2018, 07:20   #9
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For pulse plasma or gas, they are masked. Not so sure if salt bath nitrocarburizing.
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Old April 17, 2018, 11:16   #10
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Quote:
Originally Posted by Potshot View Post
Do NOT nitride the threads!
Had entire rifles salt-bath nitrided, then assembled. It tightens things up ever so slightly, but a few thousandths of difference rarely matters much. Found on my 700 a simple chase of the receiver threads was all that was needed. As for AR parts the barrels and barrel extensions HAVE to be done separately, and I haven't heard about any of those being issues to assemble. Lord knows the manufacturers aren't compensating for .003 differences pre and post nitriding, especially if they sell barrels of various finishes.

To the OP... most steels are in the 1200+ deg F to reach the Curie point. Nitriding, no matter the method, is typically within 100deg give or take of 1000deg F. I believe my former client doing SBN was just below 1000deg F as that was the melting point of his salts. It doesn't get to the Curie point of any steels, which is why it's gotten so popular. Springs are another matter however, and you do not want those treated from both heat and metal property standpoints.
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Old April 18, 2018, 05:31   #11
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And

Quote:
Originally Posted by Nathaniel01 View Post
The company offers many nitriding services, but they say the temperature for gas is 925-1050 F and the ion is 850-1100 degrees F.

I thought it would be a neat and easy way to get a nice finish with improved wear and corrosion resistance. The FAL I had nitrided was sent off somewhere by Jeff at Hillbilly Firearms, and looks great.

I was quoted a price of 50lbs of material for about $150. I paid about that much for the one rifle to get done.

Will this process burn off all the paint, or does it need to be stripped beforehand?
Strip the paint. It will contaminate the atmosphere in the oven and will cause the surface properties to be uneven (hardness
and case depth)

Also, check the barrel for straightness after nitriding as it WILL distort. Depending on outer, irregular profiles (machined areas for gas blocks, notches for pins, etc) the bore will also expand/contract and distort some. Residual stress can also cause issues, both dimensionally and with barrel harmonics. How it's placed in the oven will determine distortion as well.


During the nitriding process, your barrel will change dimensions quite a bit. Given a general change of .000006"/in/degF, and a temperature rise from room temp to 950F, your 20" bbl ends up at 20.105" or somewhere there about. The surface is hardened to about R 70, with a case depth between .005" and .020" depending on type of nitriding and cycle time,, then it cools and tries to shrink back to 20". All of a sudden all of that $$ spent on that perfect target barrel and bore are a waste. Another caveat to nitriding is if there are any tool marks in the bore when it goes in the oven, they are there for perpetuity. You will not get them out.


It's great for wear on a run n gun firearm. I have one that's been done. It is what it is though, it's not for anything you expect nail driving accuracy from.


YMMV, just some ramblings from a senile old mech engineer who has about 3000lbs of nitriding done per month @ $1.05/lb, mostly 36hr cycles on 4140/4150 alloys and 400 series stainless. Sometimes a batch of H11/H13 if we're feeling froggy.

For those interested... http://www.amesweb.info/Materials/Li..._of_Steel.aspx


Also, I defer to my sig line as well.

Edit...I just looked at the website reference by the OP... The company listed does some work for us, a little higher priced, but they know their stuff when it comes to nitriding and how to do it. You can buy with confidence from them.
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Last edited by ER; April 18, 2018 at 05:44.
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Old April 19, 2018, 20:27   #12
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Thanks for the in-depth information. I felt like I knew just enough about nitriding to be dangerous.

How does the finish look on the parts you have done look?

Would you recommend complete disassembly before nitriding?
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Old April 20, 2018, 03:02   #13
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Nitriding is a process to harden the surface for whatever purpose one desires. Honestly I have never heard of it being used for a finish treatment along the lines of parkerizing or such. It will not change the surface texture, and 4140 parts I have done usually come back colored anywhere from a very light grey (mostly ion nitrided stuff) to a charcoal grey (gas nitrided). Most of our stuff has a Rms16 or better finish when it goes out(about the same surface finish/texture as a satin stainless firearm would feel). Besides paint, I seriously doubt there is any post heat treat finish that the parts would readily accept. Parkerizing a nitrided part, in my opinion, would be and exercise in futility. Not sure about black oxide, but shops that do that anymore are few and far between.

If there's a process out there for using nitriding for a finish I would love to hear about it. Nitriding every part in a firearm would be a waste of money, but if one does it, yes it would have to be completely disassembled and degreased prior to placing it into the oven.


Nitriding can impart some super hard surface s, and with that comes brittleness. Nitrided parts do not like shock loads so it should NOT be applied to items like hammers and firing pins, and to be honest I'd be leery of it on sears and disconnectors. However, on things like bolt gun sears, cocking pieces, etc, nitrided parts can be polished for a really hard, slick surface so I could see a benefit there
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Old April 23, 2018, 14:03   #14
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Quote:
Originally Posted by ER View Post

If there's a process out there for using nitriding for a finish I would love to hear about it. Nitriding every part in a firearm would be a waste of money, but if one does it, yes it would have to be completely disassembled and degreased prior to placing it into the oven.


Nitriding can impart some super hard surfaces, and with that comes brittleness.
I'm not sure how much research you've done on nitriding, but just NO to brittleness. If that were the case NOBODY would do it to a barrel as it would become a pipe bomb. Maybe you give this last paragraph a read...

http://www.houstonunlimitedinc.com/nitriding.aspx
http://www.houstonunlimitedinc.com/implementations.aspx

"This layer is also known as the compound zone which has increased surface hardness to enhance anti-galling characteristics and lowers the coefficient of friction. This compound zone also functions as a solid film lubricant by providing a non-metallic interface between mating surfaces. Nitrogen of lower concentration continues to diffuse below the compound zone and forms a solid solution with the base metal iron. This zone is referred to as the diffusion zone and is noted for its improvement in fatigue strength."

Call me crazy but I consider "brittleness" and "fatigue strength" antonyms, as anything brittle will be most prone to fatigue.

As for finishing it Cerakote is about the only option, and it likely won't stick to a smooth (i.e. polished) nitrided surface. I'd say the best bet would be to have a bead-blasted surface nitrided, and then cerakoted, so that the paint has a rougher surface to adhere to.
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Old April 23, 2018, 20:38   #15
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You don't want to nitride the threads as it will fatigue them.

Yes I am WELL aware of the increased fatigue properties with the diffusion zone, but this isn't so much on threads. NOW, bear in mind that this is pulse plasma nitriding to ~500 micron depth. It's in the furnace for like a week.

Salt bath nitrocarburizing is a different animal, for just starters the case depth is say 20 microns...not near as deep.

Now, just YES to brittleness. The white layer remains, which is really quite brittle. This will manifest itself as a spall, and not turn your barrel into a pipe bomb because the core hardness is still quite low (and thus ductility is still high).
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Old April 24, 2018, 20:19   #16
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[QUOTE=Potshot;4573756

Now, just YES to brittleness. The white layer remains, which is really quite brittle. This will manifest itself as a spall, and not turn your barrel into a pipe bomb because the core hardness is still quite low (and thus ductility is still high).[/QUOTE]

bingo
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Old April 25, 2018, 14:21   #17
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Quote:
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You don't want to nitride the threads as it will fatigue them.

Yes I am WELL aware of the increased fatigue properties with the diffusion zone, but this isn't so much on threads. NOW, bear in mind that this is pulse plasma nitriding to ~500 micron depth. It's in the furnace for like a week.

Salt bath nitrocarburizing is a different animal, for just starters the case depth is say 20 microns...not near as deep.

Now, just YES to brittleness. The white layer remains, which is really quite brittle. This will manifest itself as a spall, and not turn your barrel into a pipe bomb because the core hardness is still quite low (and thus ductility is still high).
Well I guess I sit corrected. Sidenote, call Criterion and tell them they are doing it wrong. I'm sure they will appreciate it.

http://criterionbarrels.com/chrome-l...trided-barrels
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Old April 27, 2018, 22:43   #18
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Look, I have melonited barrels as well. I have done MANY parts with the process and it certainly has its applications. HOWEVER, it has its pitfalls too and I'd suggest understanding them fully.

Brittleness really is a factor in terms of the context of applied stress of the material in question (I am simplifying it here). The working surfaces of gun barrels really don't have much contact (Hertzian) stress, so issues with white layer really don't manifest themselves in this particular application. You may have trouble with threads though, so be alert to it. If you must go this route, use a good assembly lube on the threads, such as Copaslip.

Sidenote, as someone who's broken a lot of shit, I'm just trying to save you trouble here. You can listen... or not.
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Old April 29, 2018, 08:21   #19
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So nitriding the top of a C96 (because the bolt key might slam on it) or a, say, FAL/AR/AK bolt is a bad idea? Just confused
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Old April 30, 2018, 01:39   #20
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So nitriding the top of a C96 (because the bolt key might slam on it) or a, say, FAL/AR/AK bolt is a bad idea? Just confused
Nitrided parts do not like impact loads, especially the sharp corners. It is a process that is used in areas subject to wear from sliding, or frictional, loads. That's why it's​used as a surface treatment in gun barrels.

As Potshot mentioned, the white layer can bite you in the ass if you don't plan for it and the associated issues. In the machines we build (polymer filtration systems) the Hertzian stress is an issue due to occasional contact loading, therefore we grind .0003-.0005" off the surface after treatment.
Personally I like nitriding for the barrels of the rifles I send many bullets thru. I don't like it in target barrels, and I dang sure would never use it on a semi or FA bolt. I seriously doubt I'd ever use it on a semi or FA FCG , but I could see a use for it on some parts.
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Old April 30, 2018, 14:30   #21
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We had another thread discussing a group pile of parts to send for a hot salt bath. Talked to my barrel expert but told me to remove all barrel extensions and then extension and muzzle threads were considered an issue but if sending the barrels I planned, not to sweat it too bad. Have pile of stainless Palmetto 18" Wylde tubes and 18" AR Stoner 22 Nosler barrels all paid $79, $89 and $99 for when on sale. Some are $250 regular price but built enough already if the ones that hit the hot salt go goofy am o.k. Main issue is a lot of other parts was considering dipping have discovered not good to dip so learning more about what is best dipped and what not. Also how to mask threads if able to do myself so don't have that issue but all that need the dip gets it.
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