Abstract: A integral or monolithic nozzle segment having airfoils According to an aspect of the invention a steam turbine has a casing supporting multiple nozzle segments forming a diaphragm with the airfoils located in a channel through which working fluid flows. The diaphragm surrounds a rotary axis of a steam turbine coaxially and consists of a plurality of individual nozzle segments. The nozzle segments and the casing of the steam turbine have substantially equal thermal expansion coefficients. The casing and the nozzle segments are made of different materials and particularly different martensitic steel types. Each nozzle segment may have a core comprising martensitic steel having a minimum creep strength that fulfills the following conditions at a temperature of 580° C.: at least 105 hours under a tensile stress of at least 100 MPa or at least 125 MPa or at least 150 MPa.