It is called MA 956.
           Since the rotary exhaust temperatures are up around
           1800 F it will be needed. One can always cool the exhaust
           before it goes to the turbine but that implies a loss
           of recovered energy.


           Paul Lamar

       Hi Paul & Steve
       Looks like engine rotors from this alloy would have to be CNC machined from solid billet or forgings.
       It is NOT a castable material (unless you are willing to lose the special high-temp qualities) :

       >From Special Metals - "INCOLOY® alloy MA956 (UNS S67956), first developed as an aerospace superalloy and now used in a range of industrial applications, combines excellent strength and fabricability with outstanding resistance to prolonged exposure up to 1300°C (2400°F). Its exceptional properties result from the mechanical alloying process by which it is made; a process which allows a fine distribution of yttrium oxide particles to be incorporated into a highly corrosion-resistant Fe-Cr-Al alloy"

       >From Matweb - "An iron-chromium-aluminum alloy that is oxide dispersion strengthened and produced by mechanical alloying"

       >From wiki - "Incoloy MA956 is made by a mechanical alloying <https://en.wikipedia.org/wiki/Mechanical_alloying> rather than a bulk-melting process"

       Cheers
       Paul Randal


   How big of a billet would be needed to make some 12a sized rotors out of this material? I know it's overkill but I am curious.

   Steve Ross

   My guess is 12 inches in diameter.

   Paul Lamar


Weight or density is the problem. There is no advantage over the stock rotors.
Titanium or titanium aluminide rotors would cut the rotor weight in almost 1/2.
If you build a larger rotary engine such as the R130 or the new 16X the
rotor weight is even more. Manufacturing the rotors from TiAl would have a
pronounced effect on the weight. I am not certain about the heat transfer of
TiAl but being 50% aluminum it should be similar or higher than the cast
iron rotors. A titanium rotor would save weight and have low heat transfer
similar to SS which could provide an ideal rotor material other than cost.
That should start coming down as it is used more in aerospace and racing.

Dale Davies



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