[jywolfe]

Nitriding is a very common practice in our industry now.

We conducted lab tests a few years ago and found the results on 4140 to be excellent. A new brand of salt has emerged with our provider, specifically engineered for 8620. Results are excellent, but a slight drop in core hardness still occurs.

In our view nitriding is primarily an excellent process for corrosion resistance and is very inexpensive insurance. Nitrided parts rarely exhibit any form of corrosion. Second to corrosion resistance is the finish quality. Nitrided parts exhibit a very uniform matte finish. Last is wear properties. Barrels, op rods, gas cylinders and pistons all benefit from the enhanced wear properties of nitriding. A barrel's throat area will still erode after nitriding, but will do so at a slower pace.

Hard chrome in isolation is still a better process for slowing throat erosion and is the easiest to maintain, but most hard chrome barrels are finished with phosphating/parkerizing. What's more, hard chrome barrels do not always perform as well in terms of raw precision and consistency.

For rifles using hard chrome plating, I recommend nitriding the barrel as well. The nitriding does not alter the hard chrome plating in our experience and only enhances the barrel's overall finish and external corrosion resistance.

Taken a step further, if I was going to build a rifle that would hold-up and perform in harsh environments and under heavy use, I would nitride all parts, with the exception of the bolt, bolt internals, receiver and any roll pin or spring.

I've put a link below for you all to view the pictures of the corrosion on the barrel and piston. This rifle is for all intents and purposes new, but was fired and put away with carbon settled in the gas cylinder, on the barrel and op rod tip. If a rifle is going to be exposed to the elements and not cleaned after each and every firing, this can result. M14 rifles are an investment of time and money, and nitriding is a great way to protect them.

See this link barrel corrosion and piston corrosion: https://drive.google.com/folderview?id=0BzVSspUYSUXJcnZ4cjBpZzIteHM&usp=sharing

 

[nf1e]

Thanks Jon.
Always ready to learn.

Semper Fi
Art

 

[XM25Ren]

Jon are you saying you would not Nitride the receiver?

Ren

 

[bustedknuckles]

Keep these posts coming Mr. Wolfe!

The LRB I got from you looks like the day I picked it up. My shooting has slowed a bit so far this summer from the back surgery, but after about 1000 rounds for a rifle to look unfired is nice.

I also love the looks of the finish. Looks the best of any finish imo.

 

[KyAggie]

Very nice to know! So, if I want to make my JRA build that's still in a box ICONROLLEY as durable as possible I should have you nitride all of it except the receiver, bolt, bolt guts, springs, and pins? It has a 18" chrome lined barrel.

 

[MeatyMac]

Jon are you saying you would not Nitride the receiver?

Ren

Yes, please elaborate on Ren's question, Jon.

Thanks,
MM

 

[lysander]

Jon are you saying you would not Nitride the receiver?

Ren

Yes, please elaborate on Ren's question, Jon.

Thanks,
MM

I believe this has to do with the heat treatment of the receiver, bolt and other parts noted.

Nitriding requires the part to be placed in a bath at around 1000 F. this is above the tempering temperature used during the heat treating of these parts.

Heating these parts to 1000 F will alter the strength.

 

[bustedknuckles]

Nitride won't remove the heat treat. Unless I'm reading wrong.
http://www.blacknitride.com/frequentlyaskedquestions.html

 

[MeatyMac]

I ask because I, and several other members here, have GunWorks of Lower Alabama receivers that are factory nitride finished and it was my understand that their receivers are nitride finished after heat treating.

 

[lysander]

Nitride won't remove the heat treat. Unless I'm reading wrong.
http://www.blacknitride.com/frequentlyaskedquestions.html

It will change the temper.

The heat treat for a 8620 receiver is carburize at 1600 F for a case depth of .018", quench in oil at around 100 F, temper at 480 F for one hour, the surface hardness will be 59 to 67 RHc.

Bringing the receiver to 1000 F will change the temper.

This statement...

2. If the pre-hardened component is pre-tempered, or non-pre-hardened above subsequent temperature, core hardness will not change significantly as a result of the Black Nitriding process.

...only applies to parts that are tempered at temperatures above the nitriding process temperature. Since the tempering temperature for a receiver is below the nitriding temperature, raising the part temperature above the initial temper temperature (480 F) will significantly change the material properties...

More in nitriding:

Nitriding is carried out at temperatures below the transformation temperature of alloy steels, so that with proper manufacturing techniques, there is little or no distortion as a result of the process. Parts to be nitrided are heat treated to the proper strength level, and final machined. The parts are then exposed to active nitrogen at a carefully controlled temperature, typically in the range of 925°F to 985°F. This temperature is typically below the final tempering temperature of the steel so that nitriding does not affect the base metal mechanical properties.

In the case of receivers and bolts, 1000 F is well above the final tempering temperature, so it will affect the part's properties.

 

[lysander]

I ask because I, and several other members here, have GunWorks of Lower Alabama receivers that are factory nitride finished and it was my understand that their receivers are nitride finished after heat treating.

Factory nitriding can be different from aftermarket nitriding.

With factory nitriding, the nitriding process can be worked into the part's overall heat treatment, with aftermarket nitriding, you have to start with a heat treated part and NOT alter its properties.

By the way, barrels are tempered around 850 F to 950 F, so they do not see a change in temper. Which is why after-market barrel nitriding is much simpler.

 

[bustedknuckles]

raising the part temperature above the initial temper temperature (480 F) will significantly change the material properties

Right on, but where'd you get 480?

 

[lysander]

raising the part temperature above the initial temper temperature (480 F) will significantly change the material properties

Right on, but where'd you get 480?

That's the heat treating recommendations for carburized 8620 to achieve the harnesses I specified and maximum strength. That heat treatment gives a tensile yield of 135,000 psi, going to higher tempering temperature results in a softer core, and thus not as strong.

Incidentally, I ran across a print for an M1 receiver, they were specified to carburize at 1550 F to 1600 F, temper at 400 F for one hour, so they were a tad harder, 61 to 69 RHc.... that is in the same ball park, if not exactly the same as the M14 receiver.

Factory nitrided receivers and bolts are probably not carburized, as there is no need, the nitriding will harden the surface adequately. Un-carburized 8620 tempers at much higher temperatures. Tempering un-carburized 8620 at 1200 F will give a yield strength of 101,000 psi, at 800 F you can get the full 135,000 psi.

 

[lysander]

Something else occurred to me, it might just simply be a liability issue. The guys doing the nitriding have no clue how these critical components were heat treated by the original manufacturer, and what effect his heating the parts for nitriding will do to that heat treat. . .

Barrels are different an annealed barrel shouldn't fail under a proof load, so no worries there.

 

[bustedknuckles]

I disagree with only the part about the nitride people knowing the heat treat process. The folks from the link I gave started off in the heat treat biz.
The rest makes sense enough to me I'll take you at your word.
The barrel, gas system and the gas cylinder the only parts that really benifit having nitride anyway i guess. Unless it's more for looks.

 

[lysander]

I disagree with only the part about the nitride people knowing the heat treat process. The folks from the link I gave started off in the heat treat biz.
The rest makes sense enough to me I'll take you at your word.
The barrel, gas system and the gas cylinder the only parts that really benifit having nitride anyway i guess. Unless it's more for looks.

They know the heat treatment they give to their parts, and how they would do it, not the exact heat treatment done to a critical part by someone else....

Short of cutting and doing some destructive testing, you really can't tell much about the actual heat treatment given to a part, unless you watch them do it.

Oh, and nitriding is a far better corrosion resisting process than phosphate coating, aka Parkerizing. It also is a very good in wear resistant properties.

 

[32639]

Solution in search of a problem.

 

[XM25Ren]

I would still like to hear Jon's take on why not to Nitride the receiver.

Ren

 

[BLACKTAIL 8541]

I had a nice reply all written and lost it. Now I will try again.

I went with a Gun Works receiver because it has the nitrite process done as a part of the manufacturing process as well as the custom engraving available. The nitrite treatment gives the added benefit of corrosion protection and added wear resistance. The m-14 / M1a receiver is an expensive part, I would think it only makes sense to take advantage of this process when done as part of the manufacturing process.

John Wolfe knows his business, and I respect his opinion. He does not form his opinions out of thin air I would bet. I would also opine that he is basing his opinions on nitrating receivers based on a finished product and then treating, unless stated otherwise. If stated, then all this goes out the window. DI2

 

[M1AMODS]

I really want the Melonite treatment on my receiver, bolt and op rod & guide for it's corrosion resistance and the added lubricity and wear resistance. I hunt with my rifle, and the park finish is wearing off fast. I'm also seeing some corrosion starting to form on my bolt face. There has to be a way to get this process dialed in to work on pre-treated parts...