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Thread: Barrel Treatments (nitride/CL)

  1. #11
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    Quote Originally Posted by SomeOtherGuy View Post
    Daniel Defense is offering a CHF barrel with nitride treatment in the new 300BLK upper. AFAIK this is the first nitrided CHF rifle barrel on the market. (Glock and others have been doing nitrided CHF handgun barrels for years.)

    From what I've read, and I am only an amateur:
    1) properly done, the nitriding process is so hard and deep that hardness or wear resistance of the metal below the nitride layer becomes relatively less important;
    2) a barrel that is made of good steel and treated with a good nitriding process will last so long that seeking additional life is almost irrelevant in a semiauto-only rifle;
    2) the temperatures involved in typical salt bath nitriding may be high enough to counteract some or all of the benefit of work hardening from the CHF process.

    Constructor and Rsilvers seem to know plenty about nitrided rifle barrels, hopefully one or both of them will chime in here.

    A related question that I would like to know is this: given the apparent benefits of nitride treatment, why don't we see machinegun barrels using this approach? To my limited knowledge, most machinegun barrels are CHF and thickly chrome lined, or in a few cases lined with Stellite or other special alloys that have superior high temperature wear resistance. Does nitriding lose its benefits at higher temperatures?
    My 2 cents:

    I work as an applications engineer for a valve company. My work is mostly in critical process applications, many of which are high pressure/high temperature steam for turbines in power plants.

    In one such application, we were using 316ss with a nitride-type overlay on the seats and gate of the valve. We began to experience valve leakage (failure). What we found was not that the nitride had failed, but rather that the 316 under the nitride layer was physically compromised through heat and galling. Thus, we made the switch to a harder (though less chemical/corrosion resistant) 410 stainless.

    The point being that despite nitriding, the sub-material can be affected, particularly when heat is involved.

    Now, these are valves with large surface areas. Not gun barrels, so Robert may have different experience.
    Semper Paratus Certified AR15 Armorer

  2. #12
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    Quote Originally Posted by ASH556 View Post
    My 2 cents:

    I work as an applications engineer for a valve company. My work is mostly in critical process applications, many of which are high pressure/high temperature steam for turbines in power plants.

    In one such application, we were using 316ss with a nitride-type overlay on the seats and gate of the valve. We began to experience valve leakage (failure). What we found was not that the nitride had failed, but rather that the 316 under the nitride layer was physically compromised through heat and galling. Thus, we made the switch to a harder (though less chemical/corrosion resistant) 410 stainless.

    The point being that despite nitriding, the sub-material can be affected, particularly when heat is involved.

    Now, these are valves with large surface areas. Not gun barrels, so Robert may have different experience.
    You just drove home the point that the quality of the materials is just as important as the finishing processes.

    Coatings like chrome or processes such as nitriding can only make up for so much if the material they are applied to is of low quality.

    Start with materials like a high quality alloy CHF barrel and perform high quality processes such as QPQ nitriding to get the best all around package that will last and perform.
    Last edited by GrumpyM4; 04-19-12 at 17:21.

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    This is great information guys, thanks for the feedback!

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    Absolutely love this website, for this thread alone is worth the price of admission.

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    Quote Originally Posted by Melon View Post
    Absolutely love this website, for this thread alone is worth the price of admission.
    And that aint cheap

    From what I understand, nitriding reduced effects of friction, but not heat. I dont know what the final verdict was, but some people were discussing this in a previous thread and people were suggesting that the throat erodes quicker on a nitrided barrel(compared to a chome lined barrel) if you use it for high volume firing due to head effects.

    however, nitriding protects the barrel from friction and its a surface treatement(more uniform) so its better for precision guns.

    Chrome lining is a layer, it cannot be perfectly uniform so there are slight accuracy detriments, but it is better for high volume fire.

    Adding one to the other is pointless. I dont think you can nitride chrome. Chroming over nitrided steel offers no benefits over plain chrome lining as you are still putting a layer on it, and once it wears out, you have a hole bigger than it should be for the application. Heat effects may also be the same, but I dont know how nitriding helps the steel handle heat.

  6. #16
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    Quote Originally Posted by MegademiC View Post
    And that aint cheap

    From what I understand, nitriding reduced effects of friction, but not heat. I dont know what the final verdict was, but some people were discussing this in a previous thread and people were suggesting that the throat erodes quicker on a nitrided barrel(compared to a chome lined barrel) if you use it for high volume firing due to head effects.
    They suggested this or did they provide data? If so, I would like to see the data on this. Link?

    I'm not sure how chrome reduces the effects of heat and since much of the heat is created by friction, wouldn't reducing the effects of friction as nitriding does, help mitigate this issue from the get-go?

    And what are "head effects"? Can't say i'm familiar with the term.

    I personally think that the two main issues to look at are the hardness and the lubricity of the process/lining.

    A harder material means that it wears slower, natural lubricity reduces friction, hence reducing friction generated heat, and in the end reduces wear even more.

    Nitriding on cheap steel will result in a rockwell below that of chrome, thusly making it inferior to chrome lining in several aspects.

    But nitriding on a quality alloy will produce a higher rockwell equal to or higher then chrome depending on the alloy, thusly increasing its hardness and natural lubricity all the way around and producing a superior product.

    Also, nitriding, by its very nature, increases the natrual lubricity of the base metal as part of the chemical process, not just because it hardens it. All comparitive tests i've seen have shown that salt bath nitriding produces a much slicker surface then chrome, both with and without some form of lube.

    Add to that the superior corrosion resistance and you've got yourself a winner as far as i'm concerned.

  7. #17
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    Quote Originally Posted by SomeOtherGuy View Post
    Daniel Defense is offering a CHF barrel with nitride treatment in the new 300BLK upper. AFAIK this is the first nitrided CHF rifle barrel on the market. (Glock and others have been doing nitrided CHF handgun barrels for years.)
    LWRCi has been doing CHF, nitrided barrels for some time now. I also believe the MR556A1 has some form of nitriding performed on it's cold hammer forged barrel.

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    FWIW: The barrels on Stoner 63 were nitrided. This came out in Stoner's testimony before the Ichord Subcommittee.

    I have a copy of a 1968 .mil report where nitriding and chrome-lining was compared for barrels in high cyclic rate weapons. Chroming was considered superior, but noted that chrome over a nitrided barrel was better yet.

    Materials for Small-Arms Gun Barrels

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    Quote Originally Posted by GrumpyM4 View Post
    They suggested this or did they provide data? If so, I would like to see the data on this. Link?
    I honestly cant remember, but I know at least one guy said chrome was better but nitriding was cheaper when you factor in cost to stay epa compliant. I'll try to find the thread...


    Quote Originally Posted by GrumpyM4 View Post
    I'm not sure how chrome reduces the effects of heat and since much of the heat is created by friction, wouldn't reducing the effects of friction as nitriding does, help mitigate this issue from the get-go?

    And what are "head effects"? Can't say i'm familiar with the term.
    Head effects = heat effects. It was a mistake, which happens since I dont always proof read forum posts.

    to clerify how I understood, nitriding was better for the main part of the barrel, but chrome was better for protecting against throat erosion - which is more important for high volume barrels.

    Let me try to find the thread-which I should have done in the first place- instead of posting what is starting to look like hearsay, I'm sure. I dont know the specs for all the materials so I cant reallygive solid info at this time.

    Edit : Haha, its a thread you were active in. : https://www.m4carbine.net/showthread...=83495&page=20

    I only read it in the early stages and missed the last 12 pages or so. Just got caught up. I screwed up twice in one day... time to start reading more...

    OP the very long thread above is well worth the read.
    Last edited by MegademiC; 04-22-12 at 03:53.

  10. #20
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    Quote Originally Posted by Nmate View Post
    LWRCi has been doing CHF, nitrided barrels for some time now. I also believe the MR556A1 has some form of nitriding performed on it's cold hammer forged barrel.
    Nope.

    That's the biggest complaint about the MR556 actually aside from the stupid weight.

    I did some major barrel work on my MR556 and it machined very nicely. It is a harder metal then typical OS, but it is through hardened, not surface hardened like nitride does.

    I had the barrel QPQ nitrided as the final step in the build though so now it does have that protection and superior properties.

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