|
||||||||||||||||||||||||||||||||||||||
Member
I've been a huge fan of nitriding for a while now but im not that knowledgeable about it I was curious if anyone knows a lot about it otherwise I will get in contact with h&m basically I'm curious to how deep it treats the metal and how it affects different steels in diffent ways if I rememver correctly it affects ss not as well as cmv if no one knows these answers can you point me in the correct direction
Member
Member
Depends mostly on the application cycle time.
http://www.burlingtoneng.com/melonite.html - says it can penetrate up to 0.008"
Member
Pm "Constructor". He owns AR15 Performance and sells almost exclusively nitrided barrels. Very nice and knowledgable guy. He could probably answer a lot of your questions. Maybe he'll chime in on the thread.
Last edited by Jsp10477; 10-15-15 at 20:36. Reason: Name correction
Member
There are a lot of companies who are in over their heads when it comes to nitriding of barrels, which they outsource of course.
Some of the companies that nitride barrels fully understand what the intended application is, have been doing it for decades, and are able to correctly nitride AR barrels.
If the business customer (the retailer you buy the barrel from) doesn't know their metallurgy, then they have no clue what to ask for from the nitriding shop. It's very common in this generation, where business owners haven't taken the opportunity to get educated other than cut and paste of the services listed by the shop.
One area where this has shown up is in barrel extensions being nitrided with the barrels, and barrel extensions being nitrided on top of an existing case hardening than now creates a very brittle surface in areas you would never see this before.
Consumers, totally unaware of these realities, hear a barrel maker make claims, post figures, and come to the conclusion that the source is credible, knowledgeable, and competent, when they are in fact anything but, and are still learning about metallurgy.
Member
Have you heard that having the barrel and the extention nitrided together will cause failures or has it happened to you or do you know someone it has happened to I've also heard this but just from certain manufacturers I believe my barrel was done together but I've never heard anyone comeplain about failures with my brand of barrels I was just wondering if its theory that the extention could fail if they are done together
Member
I just know the tip of the iceberg on the subject as part of the required materials science course in engineering undergraduate work, the material on nitriding was presented under surface treatments to mitigate crack initiation and propagation, additional techniques on top of polishing and shot peening. Nitriding is a case hardening technique that improves both surface hardness and fatigue for steel alloys. From what I recall, the case depth is normally on the order of 1 mm deep, but the core of the substrate typically remains ductile. Although not covered under the basic material engineering course, from material I've read afterward, the three methods I currently know of are gas, salt bath and plasma based. Each method has it's own advantageous and disadvantages, some require operations at high temperatures, should be done as part of the heat treating process, others are low temp, and some employ even more refined techniques like QPQ (quench-polish-quench). From what little I've read on the subject, nitriding stainless does apparently reduce the inherent passivity of stainless steels - the ability to form a very thin protective oxide film.Originally Posted by Hicklinc
As for where to readily find this information, in addition to the intro to materials engineering literature, you can find specific papers on the subject using an engineering e-databases, but if you don't have access to them, then a simple advanced google search, with a file-type PDF can pull up good papers, and then search for the additional literature in the reference section.
http://www.asminternational.org/docu..._Chapter_1.pdf
I also find masters and doctorate dissertations as a good source, after the introduction section, as all dissertations require a through literature review of current techniques and practices, before demonstrating why their research is novel and pushes our understanding and knowledge envelop worthy of a masters or doctorate degree. From what I remember, most research however was conducted on big bore weapons, very little was done on small arms.
I know you're question was directed to LRRPF52, but as for the specifics for how it applies to small arms, I've read that hydrogen embrittlement is a large concern, nitriding assemblies is generally frown upon, due to the possibility of dissimilar hardenability of steel alloys used in the barrel extensions, or say on a pinned gas block. Moreover, I would also imagine that depending on the method employed, not all surfaces would be properly treated, case hardened, which may introduce internal compressive stress factors based on the temperatures required for the nitriding to occur.
Manufacturer
Issues with nitriding the barrel assembly are NOT strictly theoretical.
The most obvious issue is the extension coming loose.
The heating and cooling of dissimilar materials during the process can cause the threaded joint to lose preload.
The barrel can then come loose after healthy use and a few heat cycles.
No bueno.
Other less obvious metallurgy issues can be present as well.
Case hardening alloys are generally not compatable with nitriding.
Black River Tactical
BRT OPTIMUM Hammer Forged Chrome Lined Barrels - 11.5", 12.5", 14.5", 16"
BRT EZTUNE Preset Gas Tubes - PISTOL, CAR, MID, RIFLE
BRT Bolt Carrier Groups M4A1, M16 CHROME
BRT Covert Comps 5.56, 6X, 7.62
Member
I've tried to investigate the subject and basically came to the conclusion that there is no easily digestible, layman's version.
1) the metallurgy of the material treated affects the treated properties.
2) the type of process (gas, plasma, salt bath) affects the properties.
3) how the particular process is performed (time, heat, etc) affects the properties.
4) there are other considerations. For example, in addition to the issues like loosening extensions based on differential expansion, you can also have issues like traces of the salts remaining in small areas which could eventually cause corrosion down the line.
My takeaway is that I only deal with companies that seem to be on the ball. One criterion (necessary but not sufficient) is that barrel is treated prior to being torqued to extension & drilled for gas port.
Member
Outside of the added hardening of the barrel extension surface, the biggest factor in why extensions come loose after nitriding is because the barrel shop didn't torque the barrel extension down to 150 ft-lbs.
Since the barrel extension is case hardened 4140 or 8620, when mated with a different alloy, the diffusion of nitrogen won't be the same across an assembled part.
There are companies that have been doing this successfully for many years, and one of them is world renowned for nitrided barrels on their nation's military service rifles (full auto rated), but they are guarded about what process they use.
Last edited by LRRPF52; 10-22-15 at 11:49.
Posting Permissions
Reply With Quote
Bookmarks