Lets start with an imaginary experiment. There is an enclosed container having a wide (i.e. having sufficient surface area) bowl filled with water at the bottom. The container is in vacuum and filled only with saturated steam at that specific temperature. Both water and steam are at the same temperature and pressure. Now, some amount of superheated steam has been injected into that container. What will happen then? As per my guess, a part of the hot superheated steam will enter the water and will raise its temperature and soon the pressure and temperature inside will rise and the superheated stem will start evaporating water from the bowl until the condition inside will come to an equilibrium and all the steam will become saturated. By this process, superheated steam will loose some heat that will be used to evaporate some water from the bowl to make all the steam insdie saturated. Am I right?