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Forum Index > Rifles general discussion > Gas Nitride as a Rifle Finish

Gas Nitride as a Rifle Finish

16 Dec 2018
@ 10:04 am (GMT)

Ryan Nafe

Fellas,

I started a new job last week, and I now have access to a gas nitride service. My new employer does their own gas nitriding (as well as standard heat treatments) and I should be able to talk to someone and have just about any rifle parts treated in our gas nitride tanks. The only real limitation would be if a piece is too large to fit in the furnace, but I doubt there’ll be issues with that, the furnaces are quite large. I could certainly be wrong but the tanks I saw looked plenty big for rifle parts.

I really can’t think of anything negative about doing this, unless the cost turns out to be prohibitive. The process will make a budget carbon steel rifle into something that’s more durable and corrosion resistant than anything in bare stainless, and should give an enormous boost in barrel life.

Is there anybody with knowledge of this, perhaps a background in this type of chemical engineering, that has reason to not do it?

A very basic summary of what gas nitride treatment will do to a piece of steel can be seen here:

https://en.m.wikipedia.org/wiki/Nitriding#Gas_nitriding

Replies

16 Dec 2018
@ 08:08 pm (GMT)

Warwick Marflitt

Re: Gas Nitride as a Rifle Finish
It's been done before and by many

https://www.shootingillustrated.com/articles/2017/12/30/the-pros-and-cons-of-nitride-barrel-finishes/
17 Dec 2018
@ 08:47 am (GMT)

Warwick Marflitt

Re: Gas Nitride as a Rifle Finish
Gas nitriding or blacl nitriding not to be confused with Blacknitride an H&M trademark for FNC
17 Dec 2018
@ 08:52 am (GMT)

Paul Leverman

Re: Gas Nitride as a Rifle Finish
Ryan, I'm not sure if this nitriding is the same method they use on hydraulic cylinder rods, but if it is I would advise to not go there. Nitriding is supposed to be the be-all/end-all process on rods if you are a salesman. Years in the hydraulic trade say otherwise. Rust is not prevented by any means. Abrasive removal by simple wear of the wipers and seals is very quick, sometimes weeks. It is a cheap process, but it still has not replaced chrome and probably never will.
18 Dec 2018
@ 12:16 pm (GMT)

Ryan Nafe

Re: Gas Nitride as a Rifle Finish
Paul, it’s difficult to extrapolate or generalize from research papers or industrial use to firearms, especially since gas nitriding processes can vary quite a lot.

But from what I’ve seen, on low-alloy carbon steels (4140 is an example of a low-alloy carbon steel that’s actually quite good for nitriding, though it wasn’t designed for it) there will be a noteworthy increase in resistance to pitting in oxidizing environments, and the outer layer of a single-phase nitride process should easily be more than a couple thousandths thick.

Which would mean that the bore is likely to be much harder and thus more wear resistant, as well as being less likely to be ruined by pitting if the user is not very careful with preventative maintenance.

I highly doubt anyone would shoot one barrel enough to burn through the outer white layer, unless it was exceptionally thin. Which can be easily controlled for anyway.

-

Where I think this process could cause problems is if the bore is in poor shape at the time it’s nitrided. Because it’s going to make it that much harder to lapp or otherwise change bore or crown dimensions.
18 Dec 2018
@ 06:01 pm (GMT)

Paul Leverman

Re: Gas Nitride as a Rifle Finish
As I said, I'm not sure which process you are using. What I probably should have said was be very careful subjecting any rifle parts to any process that was not designed or developed for firearms, especially if these parts are going into a "furnace".

SAE describes SAE 4140 thusly:"4140, also known as ordnance steel, was one of the early high-alloy steels."
18 Dec 2018
@ 08:06 pm (GMT)

Warwick Marflitt

Re: Gas Nitride as a Rifle Finish
https://www.falfiles.com/forums/showthread.php?t=429188
19 Dec 2018
@ 12:54 am (GMT)

Paul Leverman

Re: Gas Nitride as a Rifle Finish
Thanks, Warwick. Now we know.

Go for it , Ryan.
19 Dec 2018
@ 01:20 pm (GMT)

Ryan Nafe

Re: Gas Nitride as a Rifle Finish
That was an interesting thread, Warwick, thanks.

The process used on the parts in that thread is a salt bath one, and looks like a QPQ sequence as well. The QPQ (quench, polish, quench) is what gives that black finish to it.

The single-phase gas process I’ll potentially use (meaning it’s just one phase, the part is put in the tank and then removed, very very basic) will give a finish that looks very similar to satin aluminum, or passivated stainless steel. Sort of like a silvery-white satin color.

That’s not really a huge difference in this case though, the end results should be pretty similar.

I did talk to the guy in charge of the Nitride department at work today though, and he said it should be no trouble at all to add some rifle parts into a run of the parts we usually make.

However:

He said they need to be bead-blasted (glass beads, fine finish) to prep the surface and then sanitized before they go into the tank. I’m a little concerned they could damage a barrel during the blasting part. But then again, we run parts with EXTREMELY tight tolerances, like +/- 0.0003”, so maybe it won’t hurt anything.

I’ll likely give it a whirl once I’m sure that the factory barrel on the 7mm Rem Mag is in decent shape.
19 Dec 2018
@ 01:29 pm (GMT)

Ryan Nafe

Re: Gas Nitride as a Rifle Finish
The real trick with this is to make sure that the bore is good before I do it, and also make sure I use some powerful solvents to get the bore completely clean as well, otherwise there could be serious problems.
19 Dec 2018
@ 01:32 pm (GMT)

Ryan Nafe

Re: Gas Nitride as a Rifle Finish
One other thing, I’m probably going to talk to someone in the appropriate engineering department and really make sure that the parameters of the process used is pretty well suited to 4140.

There’s quite a lot that can be done to modify the end results, so maybe if I get in touch with a metallurgist or materials engineer I can be sure everything will work out ok.
20 Dec 2018
@ 12:01 am (GMT)

Warwick Marflitt

Re: Gas Nitride as a Rifle Finish
Unless you do exactly what the factories do QPQ you might have issues.
20 Dec 2018
@ 02:10 am (GMT)

Ryan Nafe

Re: Gas Nitride as a Rifle Finish
Why?
 

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