Influence of Different Forming and Heat Treatment Stages on the Properties of P92‐Sheet

To improve the efficiency factor of combined cycle power plants from the state‐of‐the‐art 58% towards 65% in 2025, the steam turbine inlet temperature is to be increased up to approximately 700 °C at a steam inlet pressure of 300 bar. Modern ferritic steels like P92 however do not withstand such harsh operating conditions, necessitating the need for a cooling system. With the help of “grid sheet”, a sandwich material consisting of two face sheets and a core of woven wire mesh, the cooling is to be accomplished in the steam turbine. Since P92‐sheet needed for the face sheets of the grid sheet is not available in industry, the sheet was produced on laboratory scale. However, the used production process yielded partial inhomogeneous material properties, clarifying the need for the redevelopment of the former production process. In the new production process the cast round block was sawn to slices, which enabled a reduction of the number of required heatings above the austinitisation temperature. Using this new production process more homogeneous material properties were expected, which is evaluated using thickness measurements, chemical analyses among others. Furthermore, the effect of each process stage on the mechanical properties and microstructure were analysed.