Paul Lamar wrote:

I have seen a rotary engine that had ceramic coating on the
rotors. The ceramic came off and destroyed the rotor housings wear
surface.
The rotors are low coef. of expansion iron no less.
Dave Leonard has the engine. Dave can you please take some pictures
of the rotor and the housing in question before you leave?

Iron's CTE is anywhere from 9 to 14 (depends on alloying elements).
Aluminum 2024: 22.68
Aluminum 6061: 24.3
Alumina-based ceramics: ~8
Zirconia-based ceramics: ~10
Silicon nitride & silicon carbide ceramics: ~3

Russell Kent

Don't forget that the thin cross-section iron rotor housing liner is
bonded to the thick cross-section aluminum housing.  So, the effective
CTE for the iron liner is probably closer to 22 than to 14.   It now
occurs to me that the micro grooves in the Mazda plating may serve two
purposes:  oil retention AND stress  relief.

Aubrey


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