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View Full Version : Wear and corrosion resistance with a vengeance - nitride IDs of bores



Naphtali
07-09-2009, 07:24 PM
I am uncertain what to do with this information. I believe it may have substantial benefit, especially for black powder shooters. So I'll furnish it, and readers can use it as they wish. I am in correspondence with Mike Wright of http://www.hefusa.net/. Mr. Wright has confirmed that HEF's nitriding can be applied to INSIDE DIAMETERS of rifle barrels as long as 36 inches. If wanted, it can also be simultaneously applied to outside surfaces. The exterior finish is a dark gray-black whose ultimate color and texture depends upon finish of metal to which it is applied. This finish can be applied to lock parts also, excepting springs. And heat treat will not be affected so long as you furnish correctly the information they request at time of order.

I do not know whether build-up, if any, is irregular -- to preclude its application to target barrels -- or process-induced warpage/distortion occurs.

Firebird
07-10-2009, 12:00 AM
Problem is that the heat expansion coefficients are very different between steel and ceramics like titanium nitride etc. So you fire a couple of shots, and the coating develops all these tiny cracks as the steel expands and the coating doesn't. A couple more shots and little pieces of the coating start to peel off. This just gets worse and worse, until most of the coating is gone. And your bore - well all those little pieces of titanium nitride that got pushed down it by the bullets were hard enough to gouge out long little strips of your rifling. so there's not much rifling left. Putting a very hard coating in a rifle bore is a great idea, but so far the only one that works in real life is hard chrome plating (chromium is the hardest metallic element by the way; it's 8 on the Moh's scale, far harder than the various Rockwell scales can measure), and only if it's done very carefully so it doesn't peel or cause other problems.

theperfessor
07-10-2009, 12:22 AM
From what I read of their process the nitrogen permeates the steel instead of forming a surface layer, much as carbon permeates the steel when carburizing/case hardening. This happens through a process of solid state diffusion, where atoms move from a high concentration area (the media bath) to a low concentration area (the steel). Some steels are specifically formulated for nitriding.

44man
07-10-2009, 07:26 AM
It might be the molten salt nitride process. It will make a bore slick and that is not good for ML's that use patched balls or full size boolits.
Might be good for sabot's.

leftiye
07-10-2009, 12:34 PM
If it's nitriding the bore, then the process that firebird described will probly take place. This BTW, is the main process attributed responsibility for throat erosion in rifles. The nitriding coming about due to nitrogen from gunpowder, and 4000 degree flame temps.

theperfessor
07-10-2009, 07:02 PM
It would be interesting to put it to subjective test. Has anybody had this done? Would it make any difference If you're not shooting J-word bullets? Aren't you generating nitrogen gas and relatively high temperatures even shooting cast? Yet it seems to me that a lot of die-hard cast shooters brag about long barrel life.

One good test is worth a thousand opinions, mine included.

Nobade
07-11-2009, 06:40 PM
The main cause I see of nitriding bores is from using Sweet's or other ammonia containing solvents. Invariably when I find a rifle with a firecracked bore, I will ask what they use to clean it with and it's always a high ammonia containing solvent. Barrels cleaned with nothing but shooter's choice and JB paste never show that kind of firecracking. Perhaps cast bullet barrels last so long because of not only lower pressures, but there is never any need to remove copper?

felix
07-11-2009, 07:39 PM
Smokeless has plenty of nitrogen, and that is sufficient to lengthen a 416 leade by 0.030 in 15K shots at 35K cup min in a 22 bore. Bigger the bore, the more the area to nitride, and the less the lengthening. Using the loads most are using in the 06 military boolit matches should make the barrel last forever. ... felix