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Thread: Larry Vickers comments on chrome lined barrels vs nitrated barrels

  1. #11
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    You don't have a concern about the bore dimensions changing from the addition of the nitride?

    Who provides this service for small projects?

  2. #12
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    Nitriding or Ferritic Nitrocarbuerizing does not add to the surface of the steel. It is a conversion process that in simple terms is akin to case hardening a part while at the same time imparting corrosion resistance to carbon steels.

    FERRITIC NITROCARBURIZING accomplishes surface treatment of
    a part in the ferrite region of the iron-carbon equilibrium diagram (Fig. 1).
    As the process takes place in the ferrite region, both nitrogen and carbon
    diffuse into the steel surface. The process is categorized as a thermochemi-
    cal treatment and is carried out at temperatures between 525 and 650 °C
    (975 and 1200 °F); the typical process temperature is approximately 565 °C
    (1050 °F). The purpose of the process is to diffuse nitrogen and carbon
    atoms into a solid solution of iron, thus entrapping the diffused atoms in the
    interstitial lattice spaces in the steel structure (Ref 1).
    Process Benefits
    Ferritic nitrocarburizing improves the surface characteristics of plain
    carbon steels, low-alloy steels, cast irons, and sintered ferrous alloys. As
    described in later sections of this chapter, resistance to wear, fatigue, and
    corrosion are improved with the introduction of nitrogen and carbon.
    Scuffing resistance means the resistance to wear on the metal sur-
    face. This is accomplished by changing the nature of the surface com-
    pound layer, which is also known as the white layer. The completed
    compound layer will form with both epsilon (ε) and gamma prime (γ′)
    phases. The dominant ε-phase resists abrasive wear.
    Fatigue properties of steel are greatly improved by altering the com-
    position of the compound layer. This means that treated steel has greater
    resistance to fatigue failure than an untreated steel (Ref 1).
    Corrosion Resistance. After ferritic nitrocarburizing, steel parts can
    withstand many hours in a salt spray environment, whereas an untreated
    plain carbon steel will fail the corrosion test very rapidly.
    http://www.google.com/url?sa=t&rct=j...VEKssuyfdXWFrg

    Read the PDF in the link for a more thorough understanding on the topic.

  3. #13
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    Quote Originally Posted by PlatoCATM View Post
    You don't have a concern about the bore dimensions changing from the addition of the nitride?

    Who provides this service for small projects?
    You could try contacting HEFUSA for getting a small project nitrocarbuerized. Just keep in mind that most places like to run large batches of stuff, because whether 1 part or hundreds of parts it costs them pretty much the same to run one batch through the process.

    Here is another link that explains the process a bit differently, a good read.
    http://domino-69.prominic.net/A55B6F...arburizing.pdf
    Last edited by An Undocumented Worker; 02-25-12 at 23:20.

  4. #14
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    And here is a link detailing the QPQ process of ferritic nitrocarbuerization.


    http://www.finishing.com/kolene/qpq/


    The Kolene QPQ(SM) Process is an adjunct to Kolene Corporation's salt bath ferritic nitrocarburizing (SBN(TM)) treatment called Nu-Tride(R), whereby a mechanical polish and post salt bath oxidative treatment are provided to the nitrocarburized surface. This unique combination of salt bath treatments with intermediate surface finishing, produces a significant increase in corrosion protection while maintaining all the engineering properties initially developed through the SBN process. Additionally, the Kolene QPQ Process provides a cosmetically appealing black surface on the treated component.


    Process

    The term Kolene "QPQ" is based on a sequence of process events that occur directly following the nitrocarburizing cycle. Referring to the time-temperature profile in Fig. 1, the development of the Kolene QPQ Process may be followed. It begins with the treating cycle of the nitrocarburizing segment, i.e. pre-heat, Nu-Tride salt, Kolene KQ-5OO salt bath quench (SBQ), which produces a layer of epsilon iron nitride, Fig. 2.

    The next step is a mechanical polish of the nitride layer, thus restoring the original surface finish. This may be accomplished by vibratory polishing, lapping, centerless polishing, or by other similar means. Finally, to optimize the corrosion resistance, the component is then reimmersed in the Kolene KQ5OO salt quench bath for 20-30 minutes, rinsed and oil dipped. The resulting sequence of quench-polish-quench operations is thus termed the Kolene QPQ Process and may be expressed generically as SBN/SBQ/polish/SBQ.


    And here is a case study comparing LNC (liquid nitrocarbuerization, aka salt bath nitride) to chrome lining

    http://www.nitromet.com/A55B6F/nitro...%20Plating.pdf

    Introduction
    Experience has indicated that liquid ferritic nitrocarburizing (LNC), followed by a mechanical polish and
    re-oxidation process, has the capability of producing engineering properties on the surfaces of iron
    base components not unlike those resulting from Cr plating. This treatment, and its effectiveness in
    producing desired engineering surface properties has been reaffirmed through comparative testing and
    evaluations, herein described.

    Background
    The inherent physical characteristics of the surface layers produced by Cr plating and the enhanced
    LNC procedure provide similar engineering properties. However, significant differences relate to the
    method of producing the layers, and the resulting physical bonding with the base material. Cr plate is
    applied electrochemically to the surface of steel producing a deposition coating, a layer as shown in Fig.1.
    Whereas, the thermochemical quench, polish, quench process relies on the diffusion of nitrogen
    within a solid base material and the subsequent chemical reaction with iron to produce a microstructural
    zone of iron nitrides, Fig. 2, a layer that is integral with the base material.
    Frictional characteristics of operating surfaces are also of concern when the mating surfaces are both
    steel, or perhaps one non-ferrous metal surface, particularly within applications or systems involving
    marginal lubrication. Under these circumstances, it is noteworthy that the nitride compound formed at
    the surface during the LNC treatment has an inherent lubricity, and accordingly may function as a solid
    film lubricant.
    An evaluation of the frictional properties of the LNC nitride layer and the Cr plate, mated with a carburized
    and hardened steel surface, was made using the Block-on-Ring test, ASTM G-77 (modified). The
    results, Fig. 10, disclose a modest advantage of the LNC nitride layer, indicating a slightly lower frictional
    coefficient than the Cr plate surface.
    Last edited by An Undocumented Worker; 02-26-12 at 00:35.

  5. #15
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    Not all nitriding involves salt baths.


  6. #16
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    I think Ill stick with chrome lining until testing proves that nitrocarburizing is superior. Maybe if some reputable lab took a sample of a batch of barrel blanks from the same manufacturer, chrome lined half and nitrocarburized the other half then proceeded to shoot them to failure perhaps then we would have an answer.

    NiCorr™ surface conversion has proved more lubricious, harder wearing, more heat and corrosion resistant than the hard chrome normally used in the bore. Our barrels can handle 20,000 rounds before replacement, as compared to 6,000-10,000 rounds on a standard M4.-LWRC website
    This is basically an advertisement. Why the hell would I believe any of this? Besides, aren't there examples of chrome lined barrels that have gone 2x that amount of rounds that are still good.
    Last edited by vicious_cb; 02-26-12 at 04:03.

  7. #17
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    There is already a multipage thread on here about this topic.

    It has lots of info including on who does it.

  8. #18
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    Robb don’t run too many rounds down it before you decide to have it done!

    I have had more than a few barrels done and if given the choice will go out of my way to have it on all future builds. Running it on a few ARs with no indications of accuracy loss but then I started with good SS barrels to begin with.

    I have had at least 10 barrels on long range precision rifles done and it’s amazing! My 308 is sitting at almost 2000 rounds and running 155s at 2950 which is smoking hot. Awesome groups all the way to 1000. I clean it near every 500 rounds with just 2-3 patches just because I feel guilty. There really is no reason to clean it. Chamber hasn’t moved and I am sure the Melonite/ BlackNitride is going to extend the barrel life. Two 7mmShort Mags have just been completed so we will really study the chamber and throat wear as the 7WSM will tear up a barrel quick.

    I think more and more manufactures are looking at it and will make the switch. Maybe not the big boys but it is less expensive than chrome and produces an outstanding finish as well.

    Like I said, in addition to barrels and pistols I have done numerous AR gas blocks, gas tubes, bolts and bolt carriers with no issues and talk about a smooth and clean running system.

    Need to get one of these ARs to another LAV school so I can hear those famous words again, "DUDE that’s as wrong as two boys......."

    No one on the planet knows more about combat rifles than LAV so if he says chrome is GTG then no doubt it is. But he did say FN and HK not Bushmaster. That’s a clue!

  9. #19
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    Quote Originally Posted by Robb Jensen View Post
    Some melonited barrels will shoot really well and some don't. If a melonited barrel doesn't shoot well nothing is going to make it shoot well. Good consistent hammer forged chrome lined barrels like FN pretty much ALL shoot very well. Stainless always shoot well but not as long as heavy chromed hammer forged barrels. Just my dos centavos. This is why I want to be sure my SS410 is shooting very well and THEN meloniting it....
    Robb, Contact Mark Gordon at Short Action Customs http://shortactioncustoms.com/ he has some great experience with this and uses MMI for the work. As I understand, the heat treatment of the part at manufacture being melonited is critical.
    Kreiger barrels were used by MMI during testing and they are for certain good to go for this. My 6.5 Kreiger is a virgin, he inspected it and has just sent it off to MMI. I don't know who makes the BCM barrel, I would check into that and consult SAC.
    The increased barrel life and velocity is well worth the cost.

    well, this guy says 416R is ok, he used a Barlein, which are top notch also.

    http://www.youtube.com/watch?v=jiegZyhd5l0

    A quote from replies

    You are correct, and I tried to explain this point in the article. Once a barrel has been nitrided, the surface hardness is increased to the point that IT IS IMPRACTICAL TO RECHAMBER the barrel with conventional reamers and tools. Basically the steel is so hard it will ruin the tools. On the other hand, if you can get 50% or more accurate life from the barrel, you’ve avoided the need to set-back the barrel in the first place. Once you have a chamber in a nitrided barrel, you can’t rechamber to another cartridge type.
    GET IN YOUR BUBBLE!

  10. #20
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