Qualification of New Materials for Steam Turbines with Higher Temperatures in Order to Improve the Thermal Efficiency

Project Number 259

The investigations started under Research Project 158 on determination of modern turbine materials parameters were continued within the framework of the successor project 217 because for evaluation of the long-term characteristics of highly stressed turbine shafts and -casings as well as valves, a reasonable test duration must be achieved in order to guarantee a secured extrapolation to the planned design duration of 200,000 operating hours. Further, in the successor project, tests were carried out at 625 °C, expanding the existing database.

The present unsteady development of the creep strength graphs does not yet allow

  • reliable extrapolation of the creep strength on the determining 200 000 h-operating-/design period,
  • definition of an average creep strength rate of the new steels under investigation. These average rates are of considerable importance to the NRW reference power plant and to all other future new power plants with increased steam parameters.
  • Evaluation of the influence of applied melting and heat treatment methods on the creep strength characteristics and on the micro structure of large-volume power plant components with regard to technical ordering specifications.

Therefore, the following is planned for the successor project

  • continuation of the long-term tests with the new 600°C-steels up to a duration of t = 80,000 h,
  • ensuring the time-extrapolation concepts of conventional steels for ensuring the component characteristics of the new materials up to 200,000 h,
  • supply of long-term samples for preparation of structural figures for service life analyses.

Further expansion of the sample investigation period will create a good basis for evaluation of real components.

The following benefit for the utilities is expected from realisation of the research project:

  • Careful investigation of many production components allows covering of the design parameters for 600°C-power plants, resulting in high availability and extended plant life.
  • Increased steam parameters do improve thermal efficiency and reduce the plant CO2-emission.
  • Direct knowledge transfer among power plant operators and turbine manufacturers is guaranteed through joint elaboration of the results.

Within the framework of this research project, turbine manufacturers supply information on the state of other national and international research projects as well as on all relevant international meetings dealing with new development of power plant materials (COST522, THERMIE, MARCKO etc.).

The project is headed by Dr. Torsten-Ulf Kern, Siemens AG, and technically supported by the Technical Committee “Materials and Quality Supervision”. The results will be available in summer 2007.