. . .
Ni-Cr alloy may cost 30 - 50 times more than steel or Al on a weight basis but the power output of, say, a large turbo fan is 70 times higher than reciprocating engines on a unit weight basis.
With $400/ton steel the Ni-Cr in a GT engine is now actually cheaper than the steel in a reciprocating engine. Maybe a Wankel would be cheaper than GT but not by much.
Anyway most of the cost of all engines is labor -- that's why you see so few multi engine motor vehicles -- so it is penny wise pound foolish to spend too much time on material cost and not on design.
Turbo is DEFINITELY looking for heat resistant materials but no engine is very efficient at part load which is why series hybrids or fuel cells will eventually take over as gas reaches $20/gal.
Since Wankel is 1/4th the size and weight of reciprocating it might do well in hybrids where a lot of space and weight are devoted to batteries.
What is the efficiency of a Wankel at optimum rpm?
Besides the system could run on batteries to a gas station in case of a coolant leak, which I understand is a big disaster for Wankels.
As far as stationary power plants are concerned GE has an industrial gas turbine that is 60% efficient -- 50% higher than the best steam power plants or diesel engines. It weighs 100 tons and only runs at one rpm, however.
Large aircraft engines -- 40% efficient, at least at the one {wide open] speed they seem to spend on 90% of the flight -- will remain GT and even general aviation will eventually go turbo because of its unparalleled reliability and light weight.
Bret Cahill