The current level of the maximum temperature at steam turbine inlet is much lower than that at Gas turbine inlet is much lower than that at Gas turbine inlet because:
(a) The fuel combustion temperature in a steam generator is lower than that in a gas turbine engine.
(b) Of the corrosive nature of high temperature steam on super heater tubes
(c) The materials used for the gas turbine blades are not suitable for the steam turbine blades
(d) Unlike the gas turbine blades the steam turbine blades cannot be cooled.