Gunsmithing Thinking of Nitriding new barrel

[whatsupdoc]

I have a barrel blank coming in for a new bolt action build, going to send it out to be chambered/threaded.
When it comes back my plan is to install the barrel, put 100 rounds through it clean it and send it out to WMD to be nitrited.

Any one with experience with this?
Im looking simply to extend barrel life.

Good, Bad, Ugly?

 

[DAVETOOLEY]

One thing nitriding doesn't do is overcome heat checking. When that happens chunks of barrel will come out. You don't see precision and nitriding used often in the same sentence.

 

[whatsupdoc]

@DAVETOOLEY Thanks for the reply, was wondering why a process that allegedly increases barrel life was available yet not many PRS shooters
are using it.

That is why I asked here before I went down that hole.

 

[clcustom1911]

"Nitriding" or ferritic nitrocarburising, while great for corrosion resistance and surface friction reduction, can potentially "grow" the involved surfaces up to 0.0002" in all dimensions. If the initial dimensions are not machined to take that "growth" into account, you may have issues.

Further, from my research and experience, I believe even if the substrate metal is a mirror Polish, the Nitriding process causes a microscopic roughing of the finish. I have two AR barrels that were nitrided and one thing I had to end up doing was polishing the chambers. I was having sticky extraction issues and ripping off case rims leaving casings in the chamber with standard gas blocks.

 

[308pirate]

"Nitriding" or ferritic nitrocarburising, while great for corrosion resistance and surface friction reduction, can potentially "grow" the involved surfaces up to 0.0002" in all dimensions. If the initial dimensions are not machined to take that "growth" into account, you may have issues.

Further, from my research and experience, I believe even if the substrate metal is a mirror Polish, the Nitriding process causes a microscopic roughing of the finish. I have two AR barrels that were nitrided and one thing I had to end up doing was polishing the chambers. I was having sticky extraction issues and ripping off case rims leaving casings in the chamber with standard gas blocks.

FINALLY, someone else who gets this...……..one of the several reasons I won't buy any rifle that has been nitrided after the fact by its owner.

[sarcasm]I always wondered why we have pre and post nitriding go/no go gauges for close fitting features like splines and tight clearance holes....[/sarcasm]

One minor clarification. Ferritic nitrocarburizing is only one of the several steel nitriding processes in common use. Gas nitriding and Plasma (aka Ion Discharge) nitriding are two that are also very common and neither uses molten cyanide salts to provide the free nitrogen. I know gas nitriding will not increase the surface roughness of a part. I don't know if plasma nitriding will or won't, none of my customers have specified that method of case hardening yet.

Notice also I said "method of case hardening". Increasing the surface hardness (to a specified depth) of the steel, not friction reduction or increased corrosion resistance, is the reason why parts are nitrided in the first place. Those other two benefits are nice side effects, as is the darkening that has led so many internet engineers to call nitriding a "coating".

 

[clcustom1911]

FINALLY, someone else who gets this...……..one of the several reasons I won't buy any rifle that has been nitrided after the fact by its owner.

[sarcasm]I always wondered why we have pre and post nitriding go/no go gauges for close fitting features like splines and tight clearance holes....[/sarcasm]

One minor clarification. Ferritic nitrocarburizing is only one of the several steel nitriding processes in common use. Gas nitriding and Plasma (aka Ion Discharge) nitriding are two that are also very common and neither uses molten cyanide salts to provide the free nitrogen. I know gas nitriding will not increase the surface roughness of a part. I don't know if plasma nitriding will or won't, none of my customers have specified that method of case hardening yet.

Notice also I said "method of case hardening". Increasing the surface hardness (to a specified depth) of the steel, not friction reduction or increased corrosion resistance, is the reason why parts are nitrided in the first place. Those other two benefits are nice side effects, as is the darkening that has led so many internet engineers to call nitriding a "coating".

Thanks for that clarification. Was going on memory and had my head up my tail when I forgot to mention the other methods of nitriding. I was referring specifically to salty bath nitriding.

Reference the reasoning nitriding has been used, I Agree 100%. Case hardening primary with side effects of friction reduction, color, and corrosion resistance. It's definitely not a coating.

The FNC process my barrels went through during their manufacturing process was the pre-heat, quench, polish, quench (QPQ) or Salt Bath Nitriding.

If I'm not mistaken the Nitriding processes you referenced were PVD processes, etc, no?







If you can't be safe, be deadly

 

[308pirate]

Thanks for that clarification. Was going on memory and had my head up my tail when I forgot to mention the other methods of nitriding. I was referring specifically to salty bath nitriding.

Reference the reasoning nitriding has been used, I Agree 100%. Case hardening primary with side effects of friction reduction, color, and corrosion resistance. It's definitely not a coating.

The FNC process my barrels went through during their manufacturing process was the pre-heat, quench, polish, quench (QPQ) or Salt Bath Nitriding.

If I'm not mistaken the Nitriding processes you referenced were PVD processes, etc, no?

PVD is a surface coating that doesn't penetrate into the crystalline lattice of the steel. It uses ionization to create a reactive gas that forms a surface buildup on the metal, not in it.

Gas nitriding is basically an oven from which all air is evacuated and replaced with ammonia supply the N2 for diffusion . Plasma nitriding uses ionization of pure nitrogen to both release nitrogen ions and heat the surface of the steel to be treated.

QPQ is just doing two cycles of salt bath nitriding with a polishing step in between. Not all salt bath nitriding processes are QPQ.

Also, salt bath nitriding is not the same as ferritic nitrocarburizing. People often confuse the method of releasing the elements to be diffused into the steel (salt bath, gas, ion) and the elements themselves (carbon, oxygen, nitrogen).