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View Full Version : High temperature alloy. Suggestions?



Tony Hanna
04-08-2007, 05:57 AM
I'm looking for something that will survive directly in the exhaust stream preturbine without warping. Requirements are that it has to be available in 1/8" or 3/16" plate and round stock. Also, the less heat expansion, the better. I was initially considering trying to pick up some inconel scrap at work, and I may still, but I thought I'd explore other options as well.
Would any of the commonly available grades of stainless be worth considering?
None of the local metal supply places have anything to offer in the way of superalloys.:(
Thanks,
Tony

Marcus86GLHS
04-08-2007, 06:08 AM
if you require a low coefficient of thermal expansion than stainless steel is not a good choice, best would be Inconel 600 or 625 which is available in many standard forms and is a lot better against high temp corrosion than stainless steel.

Waspoloy is another good choice.

Also look at Inconel 718 which would be less expensive but does have more Fe content than IN 600, and has a higher CTE, but is superior to SS.

The ultimate? Inconel 100 or C101. but those are way exotic.

Tony Hanna
04-08-2007, 06:23 AM
if you require a low coefficient of thermal expansion than stainless steel is not a good choice, best would be Inconel 600 or 625 which is available in many standard forms and is a lot better against high temp corrosion than stainless steel.

Waspoloy is another good choice.

Also look at Inconel 718 which would be less expensive but does have more Fe content than IN 600, and has a higher CTE, but is superior to SS.

The ultimate? Inconel 100 or C101. but those are way exotic.

Well, for what I'm doing, I guess I could work some room for thermal expansion into the design. My biggest problem is that everything you just listed is going to be next to impossible for me to find locally unless I get really lucky and stumble across some scrap inconel plate and round stock at work. I wonder how 309 would do if I allowed it the necessary room to grow? Crap, I hadn't even considered the constant heat cycling this thing is going to see either.:banghead:

Tony Hanna
04-08-2007, 06:43 AM
For reference, here's what I'm trying to build.
http://www.turbo-mopar.com/forums/showpost.php?p=144808&postcount=65
Thanks,
Tony

Marcus86GLHS
04-08-2007, 08:44 AM
looks like you will have to make design considerations for the valve's pivot mechanism in your item to achieve good reliability and minimize exhaust leaks at the pivot.

what material is the exhaust header? looks like mild steel is that right? if so your flange should be the same/similiar material (all the mild steel groups in the 1000 series have nearly identical CTE's)....perhaps use a carbon bushing at the pivot points. carbon having the lowest CTE, should work well in this application since its lubricity will not be effected too much at say 1900 degrees EGT. You can machine the bushing out of common graphite plate, making sure to orient the graphite expansion plane in the same direction as the pivot arm.

As the pivot arm comes up to temp the OD to ID clearances w/ the bushing should be calculated to avoid binding at temp.

that sucker is gonna get hot. i like the concept.

Tony Hanna
04-08-2007, 03:03 PM
looks like you will have to make design considerations for the valve's pivot mechanism in your item to achieve good reliability and minimize exhaust leaks at the pivot.
what material is the exhaust header? looks like mild steel is that right? if so your flange should be the same/similiar material (all the mild steel groups in the 1000 series have nearly identical CTE's)....perhaps use a carbon bushing at the pivot points. carbon having the lowest CTE, should work well in this application since its lubricity will not be effected too much at say 1900 degrees EGT. You can machine the bushing out of common graphite plate, making sure to orient the graphite expansion plane in the same direction as the pivot arm.

As the pivot arm comes up to temp the OD to ID clearances w/ the bushing should be calculated to avoid binding at temp.

that sucker is gonna get hot. i like the concept.

Sorry, I should have been more specific. The picture of the header and gadget was borrowed from a random website just to illustrate the idea. I believe it's on a 280 ZX. Due to space limitations I'm going to be using a ported stock manifold drilled and tapped for the Holset flange.

I'd given a little thought to making some sort of bushing or seal for the pivot, but to keep it simple, I think I'm going to try to allow just enough clearance that it doesn't bind and hope it doesn't leak too bad once it comes up to temperature. Also, I figure the side opposite the arm can be a blind hole so that eliminates the possibility of a leak there.:thumb:

I really do need to keep it simple as I don't have access to the equipment to do any machine work. I'm going to have to get John to drill the hole for the pivot at work and I'll end up cutting the flapper by hand and setting the clearance with a feeler gauge and file.:o

Thanks,
Tony