Lynn E. Hanover
I have an inconel tangential
muffler/manifold; followed by a resonator (of my own design) that is 321 SS. (see
photo). The joint at the 321 in clamped, and there is a support at the aft end.
The inconel is .050” thinck. I now have over 60 hours of operation (and temp
cycles measured in the hundreds) and all is well. True; that is not REAL
long time, and I do periodic inspections.
Inconel
is often encountered in extreme environments. It is common in gas turbine
blades, seals, and combustors, as well as turbocharger
rotors and seals, high temperature fasteners, chemical processing and pressure
vessels, heat exchanger tubing, firearm sound
suppressor blast baffles, and Formula One exhaust systems.[1][2][3]North American Aviation constructed the
skin of the X-15
rocket plane out of an Inconel alloy known as "Inconel X".[4]
The big advantage to inconel for our
application is its high temperature strength, and resistance to stress
corrosion, intergranular corrosion exacerbated by stress, which the other high nickel
alloys are subject to.
It comes in different alloys; 600, 625,
690, and 718. The 690 is used extensively for cladding of nuclear fuel
rods in power reactors, and was developed with low cobalt to reduce the induced
radioactivity from the CO-90 isotope. Inconel is subject to work hardening,
so it is tricky to machine. This varies a bit from one alloy to another, and I
don’t know what alloy mine is, but I think it is 625. I suspect the
post weld heat treatment is an important factor.
I thought the internals of the 321
resonator would not last much beyond about 50 hours, but it is still solid as a
rock. The expansion of the exhaust into the manifold/muffler drops the
temp considerable, so I now think the 321 will last a long time.
So, Bob; if you don’t fly too soon
and too much, I’ll be ahead of you accumulating hours – and I’ll
let you know if I see any adverse effects.
David Atkins has an inconel
manifold/muffler on his plane, and quite a few hours. Maybe someone knows
how many.
Al