Nitriding

Anyone here ever nitrided (i.e salt bath nitriding or plasma nitriding) their firearms? And who can do it in NZ?

I've noticed that Mauser and Rigby are now nitriding some of their high-end guns. While it looks like blueing (black-ish in colour), it's not a finish, but rather a surface hardening treatment which changes the structure of the steel itself. Much more durable and corrosion proof than stainless as well.

I came across these guys online. NZ company. Not sure if they'd work on firearms? Heat Treatments Ltd - heat-treating and surface finishing services for metals and alloys

If any of those metal treating processes could be applied to guns, why would you stick with regular blueing or plain stainless?

US benchresters had a go at nitriding the barrel bore on their rifles some time ago but it can't have been helpful (certainly for accuracy) because it faded away as an internet and magazine topic.

Oh, okay? Interesting.

But for a hunting gun - perhaps the superior corrosion resistant qualities will make up for the loss in absolute precision?

Keen to get my bolt done.

Seems to be pretty popular in the USA.

I used to get a lot of nitriding done at heat treatments ltd of injection mould and machine parts. Excellent process that required very little rework after treatment if any. 65 HRC surface hardness around 5 thou deep and can be double dipped for extra depth. Not sure about the corrosion resistance bit while It did improve it was definitely not like stainless. We still used stainless for mouldings corrosive plastics.

Accepting that nitriding makes it more difficult to work on in the future, it's good. Finish is obviously hard as hell, the process is cheap - elsewhere you pay by the kilogram of material being done, so guns are cheap to do (don't know about here), and it looks good. Same as bluing, it doesn't coat the surface, so any imperfections visible pre-treatment will be visible post treatment.

If I've got it correct the actual nitriding is the part that gives surface hardness in a thin skin layer on the exposed metal by forming metal nitrides ... while the black finish comes from a second surface oxidizing step, so more or less an aggressive hot salt bluing process, which explains why they look so similar. There are a couple different types of nitriding as well, so that's another rabbit hole to go down. Plasma vs gas.... something about being able to mask off surfaces from being nitrided with plasma but not gas??

Downside is that if you ever want to drill, cut, or otherwise modify the gun, you're going to need to break through that high carbon skin first. Not a huge deal in all cases, but it is a factor.

I haven't worked it out fully, but have been thinking that the ultimate hunting/tough use rifle would be nitrided then phosphated/parkerized. You would lose the nitride-oxidized surface layer when the phosphate went on, but the phosphate layer would more than offset that. Depending on if you wanted a specific look (zinc-grey or manganese-black), or planned to then paint, oil, bake a finish etc you could keep going....