Material Qualification for the 700/720 °C Power Plant (MARCKO 700)
Project Number 281
Material is gaining central importance in case of increasing steam parameters to temperatures up to 720°C. Martensitic 9 – 12%Cr steels cannot be applied at in this temperature range; it is, however, the structural material in many areas of the power plant where temperatures do not reach the peak rates mentioned.
In the area of the steam generator, the main and key components are the thin-walled membrane wall- and superheater tubes as well as the thick-walled components header and pipe. For the membrane wall, the basic dates for the new German material 7CrMoVTiB10-10 are already on hand. This material is to cover the temperature window between 490 and 535 °C material temperature. For temperatures above some 535 °C, materials from the COST522- and MARCKO-DE2-programme (12CrCoMo and Alloy 617) are applied.
These materials have an increasing degree of complexity, i. e. with regard to chemical composition and heat treatment – resulting from demands for time- and temperature-related strength/ductility.
While in the range up to 550 °C mainly low-alloy steels were applied, the long-term characteristics (strength, forming, creep) of which were well researched, this basis is available only deficiently for the martensitic steels and for the nickel-based materials it is fragmentary. Besides the mere codes, this relates mainly to the large-scale processing of the new materials.
The unacceptable economic as well as legal responsibility risk for the manufacturer which is due to the high net product potential e. g. of a large boiler, can only be borne within the framework of a public support joint project.
The experimental investigations (creep- and component tests) to be realised within the framework of this project will create the basis for the scientific evaluation of the long-term characteristics of the materials 7CrMoVTiB 10-10, 12 CrCoMo and Alloy 617 under operating conditions and thus for their licensing as construction materials in pressure vessel construction as per the European guideline for pressure vessels.
The project results will enable planning of material-adapted recurring testing. Further, possibilities will emerge to make use of modern methods for “Design by Analysis” which in contrast to standard design will make possible complete exploration of the material potential.
The project will be headed by Professor Karl Maile, Stuttgart Materials Testing Institute, from August 1, 2004, to June 30, 2008. It will be financed mainly from BMWi funds (Joint MARCKO programme: “Material realisation low-CO2 coal-fired power plant”, Project No. 0326894) and Research Association of the Working Group of the Iron- and Metal-processing Industry e.V. (AVIF, Project No. 215). VGB participates in industrial financing and its Technical Committee “Materials and Quality Supervision” is supporting the investigations.
The project is technically assigned to the VGB main research programme “New materials for power plants” (NWK) and follows the research project 198 (AVIF 130, BMWi 0327062).