For the little I know about turbine engines, I know that these run at enormous high temperatures and thus, need nickel based superalloys.
From what I know, jet engines use a smart use of air flow throughout the parts of the engine (such as the combustion chamber) in order to make an air layer of protection between the metal walls and the flames.
... But you have to keep a balance between air cooling with the energy used to compress the air in order to increase efficiency.
Well, in the scenario that one wouldn't use such superalloy because of its high price, if someone were to inject water with the combustion jet ejecting the combustion chambers directly to the turbine, would the water avoid the material melting?
... Or it would just make unnecessary steam?