Extreme LC200N (Accidental) Corrosion Test

[Evil D]

Looks like some metal memory action going on.

It got "frozen" by corrosion, while the lock bar was under full tension, creating a fatigue crack in the liner. Maybe?...

I dunno. In the position of his first pic it's partially open, which really doesn't have the lock bar under any more tension than when the lock is closed. I wonder if you left the same knife in the same environment in the fully closed or open position if it would still have broke?

[ChrisinHove]

I’d never heard of hydrogen embrittlement. Fascinating.

[PayneTrain]

Also, as I understand it, the liners are made from LC200N not 316. Something I just realized... In the first picture I posted you can see a slotted screw going into the hull. It's either 316 or 304, and has been there for a decade or more with no corrosion. Not sure why they wouldn't just use 316 for the liner, it has to be cheaper.

I don't think they're LC200N. Spyderco just calls them "stainless steel":
https://www.spyderco.com/catalog/detail ... -Leaf/1091
Definitely makes more sense to use a more stainless steel if edge holding isn't a concern, especially since they're cheaper and that's a pretty good slab of them on each side. I bet it's a 300-series stainless.

Still don't get why it broke though. I'd personally see if the forensics lab at Spyderco W&R would be interested in making a judgement on it. I bet they'd hook you up somehow. Worth a shot if you ask me! I mean, the most likely thing I can think of is corrosion weakened the bend and created a stress concentration, but the rust looks so superficial it just doesn't seem obvious that it contributed to the failure.

[BornIn1500]

I don't think they're LC200N. Spyderco just calls them "stainless steel":
Definitely makes more sense to use a more stainless steel if edge holding isn't a concern, especially since they're cheaper and that's a pretty good slab of them on each side. I bet it's a 300-series stainless.

I'm confident that Spyderco has told us numerous times that the liners are also LC200N, not just the blade. We've had this discussion before on this forum. But maybe I'm wrong...

[Sumdumguy]

Looks like some metal memory action going on.

It got "frozen" by corrosion, while the lock bar was under full tension, creating a fatigue crack in the liner. Maybe?...

I dunno. In the position of his first pic it's partially open, which really doesn't have the lock bar under any more tension than when the lock is closed. I wonder if you left the same knife in the same environment in the fully closed or open position if it would still have broke?

I have no idea, just spitballing.

Closed or partially closed, the lockbar is under tension. When locked there's very little tension on the lock bar.

Combine that that tension(pulling the steel apart, kinda), with surface damage from such extreme exposure, "freezing" the metal and maybe it can create a shear point where added pressure can cause it to fail.

Perhaps the direction the grain could have an affect?

[Evil D]

Looks like some metal memory action going on.

It got "frozen" by corrosion, while the lock bar was under full tension, creating a fatigue crack in the liner. Maybe?...

I dunno. In the position of his first pic it's partially open, which really doesn't have the lock bar under any more tension than when the lock is closed. I wonder if you left the same knife in the same environment in the fully closed or open position if it would still have broke?

I have no idea, just spitballing.

Closed or partially closed, the lockbar is under tension. When locked there's very little tension on the lock bar.

Combine that that tension(pulling the steel apart, kinda), with surface damage from such extreme exposure, "freezing" the metal and maybe it can create a shear point where added pressure can cause it to fail.

Perhaps the direction the grain could have an affect?

Well I started to think about all the knives sitting on vendor's shelves right now that are closed/under tension but of course those aren't sitting in water/chlorine so I guess that's very different.

[JoeBleaux]

I don't think they're LC200N. Spyderco just calls them "stainless steel":
Definitely makes more sense to use a more stainless steel if edge holding isn't a concern, especially since they're cheaper and that's a pretty good slab of them on each side. I bet it's a 300-series stainless.

I'm confident that Spyderco has told us numerous times that the liners are also LC200N, not just the blade. We've had this discussion before on this forum. But maybe I'm wrong...

FWIW, In Nick Shabazz's youtube review he says that Sal told him the liners are LC200N.

[curlyhairedboy]

That definitely looks like stress corrosion cracking to me.

[Abyss_Fish]

Thanks for sharing this! I think most people finding something like this would simply sigh and throw it away. Spyderco is as much a knife research company as they are a knife making company and testing the limits of designs like this does nothing but help us all. I’d love to see how a regular comp lock like the standard pm2 would react to this sort of gauntlet, I doubt there’d be much left :D

[Ngati Pom]

If the liners are LC200 , wasn’t there something about LC not coping well with Sulphur.
This was when the detention balls were changed out for ceramic. Maybe there was a trace in the mud/slurry?