I have an old 12A rotor around that I pried the 3 mm seal and springs
out of. The seals look good but the end of the springs was worn
to a sharp point where they contact the bottom of the seal. 
I imagine this is so because the seal and slot was carboned up so 
bad no lube oil could get down there and cool or lube the spring. 
The side wear on the seal itself was minimal. Tracy's seals from 
his 860 hour engine had more side wear than this seal.

I was able to break the cast iron seal easily while prying it
up from the slot. It occurred to me the way to make better apex
seals is make them out of 4130 and heat treat them so they are
tough and hard to fracture with detonation. Then use a 
D-gun to coat them with tungsten carbide on the top wear surface.

You can clamp a bunch together when coating them to cut the cost.
They then must be ground and polished to get the nice radii on
the top.

Also nitriding the top of a heat treated 4130 seal might also 
work and that would be a LOT cheaper.

I just don't think those cast iron seals are the optimum solution
for turbo engines.

The silicon nitride ceramic seals are nice but they can be 
fractured by detonation as well and they are very expensive.

Paul Lamar
 
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