John,
Have a look at this nickel based, high heat resistent alloy made by
Haynes International. It's called HASTELLOY=AE S alloy. You can see it
at this Haynes Web site:
http://www.haynesintl.com/Salloy/HastelloyS.htm

Haynes makes exotic alloys & was originaly founded by a man names
Elwood Haynes who was the inventor of the following:
1=2E) Stainless Steel.

2=2E) The 1st internal combustion powered car.

3=2E) slot car racing.

4=2E) An alloy called stellite.

I only know all this because he hailed from my home town of Kokomo,
Indiana which is where Haynes still manufactures many of it's alloys
today. Hope this helped...
-Wayne-