Wanted pristine but broken Dilvar head stud

[reclino]

I want to take a look at and have a materials engineer evaluate one or more failed Dilvar head studs. It might help to have one that has not yet failed. The perfect example would have no other damage or corrosion, but appeared to fail for no good reason.
I would assume many engine builders have a bucket of the things lurking in a corner.
I will post all details of the informal report I get. I hope to be able to have a chemical analysis run at the least so we all know what the heck this stuff is made of. I assume it is a variation on Kovar a Nickel-Iron-cobalt alloy.
thanks
David

[totle]

I have, but I live in Norway. Where are you?

[reclino]

I live in North Carolina, USA. I am betting there is someone closer.
David

[unclebilly]

I doubt it is kovar given that kovar has a very low thermal expansion and the thermal expansion of the studs must roughly match the material of the cylinder and head to ensure consistent clamping force of the gaskets during the thermal cycling of the engine during operation.

My first patent was for a thermal clamping mechanism for a solid oxide fuel cell stack. In many ways, the system is very similar to the head studs on a 911...

[IMR-Merlin]

Holy crap, do we have a rocket scientist among us!?!?!
Or is that electrical?

Originally Posted by unclebilly

I doubt it is kovar given that kovar has a very low thermal expansion and the thermal expansion of the studs must roughly match the material of the cylinder and head to ensure consistent clamping force of the gaskets during the thermal cycling of the engine during operation.

My first patent was for a thermal clamping mechanism for a solid oxide fuel cell stack. In many ways, the system is very similar to the head studs on a 911...

[patina]

David I'm in NC and just pulled some this week - shoot me a PM.

[Miguel Antonett]

Originally Posted by IMR-Merlin

Holy crap, do we have a rocket scientist among us!?!?!
Or is that electrical?

No maaaan, that's spelling... :-/

[RarlyL8]

To what end?
I can tell you what you will find after the failure mode evaluation, heat stress and oxidation fatigue.
We have an engine apart now where the studs were all intact. The mechanic saw a rust spot grabbed it and snapped the stud off in his hand.

[chris_seven]

I have posted a few threads on this subject on the same thread cross-posted on the Engine Building' Forum.

I hope these comments add some value.

[Ronnie's.930]

Originally Posted by chris_seven

I have posted a few threads on this subject on the same thread cross-posted on the Engine Building' Forum.

I hope these comments add some value.

Chris, I've just read your posts in that thread and they really answer a lot of questions about why those studs are so problematic - thanks for taking the time to share all that info!

[RarlyL8]

One of the issues with Austenitic precipitation hardening stainless steels is that they do have a strong tendency to suffer from Stress Corrosion Cracking (SCC) particularly in the presence of Chlorides. The relatively high level of carbon found in Dilavar does it no favours in this respect.

I think that is what I said, only in English.

[unclebilly]

Originally Posted by RarlyL8

I think that is what I said, only in English.

What! That was a bunch of gibberish!

SCC is stress corrosion cracking and can be from chlorides, H2S, etc. Carbon is it's own element and not a chloride. Chlorides have the element Chlorine present...

[RarlyL8]

Doesn't matter what the cause is, stress cracking, fatigue, oxidation, etc are all known contributors to dilavar stud failure. This is common knowledge. I'm just curious what the poster is hoping to gain from an analysis that isn't aready known. Maybe just doing it out of curiosity?