How does Titanium handle "hard use"/full auto?

[JoeK]

So I am wondering about the various "hard use/full auto" rated suppressors made from Titanium. Airlock and some other ultralight hunting suppressor guys have been saying don't heat their titanium cans above 800* or it is permanently weakened.

Can anybody explain the dissonance here to me? I've seen plenty of cherry red titanium torture tests out there and it makes sense that Inconel can's (and now Haynes 282 is a thing) can handle that sort of hard use but what's the deal with Titanium for hard use cans?

 

[JoeK]

noone can hep me understand this? seems contradictory...

is it just that these ultralight cans are pushing the limit of how thin the material can be and still contain the pressure to the point that heat stressing it above 800* becomes a problem.
Meanwhile the harder use designs have thicker(heavier) material designed to contain the pressure using a thicker walls based around the reduced strength, heat stressed titanium?

 

[Formidilosus]

noone can hep me understand this? seems contradictory...

is it just that these ultralight cans are pushing the limit of how thin the material can be and still contain the pressure to the point that heat stressing it above 800* becomes a problem.
Meanwhile the harder use designs have thicker(heavier) material designed to contain the pressure using a thicker walls based around the reduced strength, heat stressed titanium?

“Full auto” does not mean glowing red. Once Ti changes color during firing, it has lost its temper- or part of it. The most oft used “full-auto” test is the SOCOM reliability test- it does not cause cans to change color during firing.

 

[JoeK]

So is the ability of Ti cans to handle hard use, high heat firing schedules just based on material thickness?

I get the distinction that full auto rated is less than glowing red per SOCOM schedule. It seems clear though that these cans are actually designed to handle higher firing schedules since many of them at least appear to hold up to these glowing red torture tests. Heck Form just put up a pic of the 8.5oz AR can in development glowing red. maybe that does cause non-obvious degradation of the cans but they still at least APPEAR to handle it ok, for a while.

I have no intention of testing the limits of my ultralight hunting cans, and I also understand why a manufacturer would rate a conservative firing schedule and say "don't heat it above 800*" I've just been wondering how other cans/manufacturers are using presumably the same Titanium material, but boasting how they can handle hard use.

@Formidilosus if you wanted a can designed for hard use AR mag dumping would you reccomend going with inconel/Haynes or would you be good with a Ti can that's designed with that use in mind (obviously not an ultralight hunting can)?

 

[Formidilosus]

So is the ability of Ti cans to handle hard use, high heat firing schedules just based on material thickness?

No. Once past a certain temperature, the Ti loses its temper. A thicker can will take just a bit longer- though not as much difference as people would think. Of course, extremely thin Ti goes fast.

I get the distinction that full auto rated is less than glowing red per SOCOM schedule. It seems clear though that these cans are actually designed to handle higher firing schedules since many of them at least appear to hold up to these glowing red torture tests. Heck Form just put up a pic of the 8.5oz AR can in development glowing red.

You responded to “form”.

maybe that does cause non-obvious degradation of the cans but they still at least APPEAR to handle it ok, for a while.

They are safe after the 180 rounds cyclic event. However, baffles have eroded and there is degradation. I metered the US gas gun can you mentioned the other day, it is now about 2 dB (A) louder than before the event.

I have no intention of testing the limits of my ultralight hunting cans, and I also understand why a manufacturer would rate a conservative firing schedule and say "don't heat it above 800*" I've just been wondering how other cans/manufacturers are using presumably the same Titanium material, but boasting how they can handle hard use.

“hard use” is relative. There are Ti cans that 30-60 rounds rapid fire semi-auto damaged them. Then there are cans that can do the full SOCOM reliability test without failure. There almost no cans that you can put in a belt fed and shoot until glowing, then barrels and do it again, etc continuously. Remember- it doesn’t take all that many rounds full-auto on an M4 to burst the gas tube.

@Formidilosus if you wanted a can designed for hard use AR mag dumping would you reccomend going with inconel/Haynes or would you be good with a Ti can that's designed with that use in mind (obviously not an ultralight hunting can)?

I would use the US can that I showed- it was designed by me and another for that use. It has inconel and steel where needed.

 

[PathFinder]

6-4 TI is a balance of alpha and beta phase microstructures. Without going into too much detail, those two microstructures lock each other together and increase the strength of the material.
If heated above the beta transus, the microstructure becomes all beta phase and significant grain growth may occur. This makes the material significantly more ductile, with a lower yield strength. The rate at which it cools determines the final state of the microstructure.
Basically keep it below the beta transus and it should be fine. If it goes above that, there are ways to heat treat it and get it back to the right alpha/beta balance.

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[JoeK]

Thanks for the in depth response I do appreciate it. I had meant to also propose the alternative of a multi-material can and it's interesting that's where you went with developing such a can. it seems to make good sense albeit more complicated manufacturing. Impressive that you've got it down to 8.5ozs that's obviously appealing I'll keep my eye out for that release.

They are safe after the 180 rounds cyclic event. However, baffles have eroded and there is degradation. I metered the US gas gun can you mentioned the other day, it is now about 2 dB (A) louder than before the event.

This is what I was suspecting. and it follows that using inconel or other more durable alloy in the blast baffle and any other high wear areas while still using Titanium tube assembly to keep weight down is a good recipe.

6-4 TI is a balance of alpha and beta phase microstructures. Without going into too much detail, those two microstructures lock each other together and increase the strength of the material.
If heated above the beta transus, the microstructure becomes all beta phase and significant grain growth may occur. This makes the material significantly more ductile, with a lower yield strength. The rate at which it cools determines the final state of the microstructure.
Basically keep it below the beta transus and it should be fine. If it goes above that, there are ways to heat treat it and get it back to the right alpha/beta balance.

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thank you for explaining the metallurgy, do you know Does the color change (glowing) roughly correlate to the 800* mark and this "beta transus"?

 

[PathFinder]

Glowing is definitely above the beta transus. When the oxidation goes from straw colored to dark blue/purple, that's another indicator that it has been that hot. Right around 800f

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