Damage Development of 9 % Cr Steels

Project Number 211

The aim of the project is the expansion of the knowledge about the time dependant course of the damage due to creep in modern 9 % Cr Steels based on experimental Investigations under practical loading conditions. With regard to that, methods for the monitoring and for the avoidance of component failure due to creep damage should be converted into regulations. As model materials the martensitic steels X10CrMoVNb9-1 (P 91) and X11CrMoWVNb9-1-1 (E 911) are considered whereby variants of P 91 with different thermal treatments are investigated additionally.

The project consists of a multitude of experimental investigations:

  • Operational measurements in the Schwarze Pumpe power plant,
  • Creep rupture tests on smooth and notched hollow zylinders under multiaxial load,
  • Creep rupture tests on smooth circular tensile specimens under uniaxial load.

Above that, metallografical and fractografical investigations are necessary to be able to conduct the characterization of the material's state of damage. Especially the formation of segregations and pores as well as the change of the grain size are fields of interest.

Parallel to the experimental investigations numerical calculations are conducted under the usage of the finite element method. These numerical analysises are used for both, the comparison of postcalculation and operation loads in the Schwarze Pumpe power plant as well as the precalculation of laboratory tests. In the course of this the degree of multiaxiality at the power plant is interesting for the determination of the geometry of the hollow cylinders according to the relations in practice. Beyond that it is possible to evaluate transfer activities and changes of the multiaxiality based on inelastic finite element calculations with respect to the operation time.

This project is conducted by the Staatliche Materalprüfungsanstalt (MPA) of the University of Stuttgart, Prof. Eberhard Roos together with the Siempelkamp Prüf- und Gutachtergesellschaft, Dresden. The project should be processed in the period between July 2000 and June 2003.