Criteria for Creep assessment of High-temperature Components Made of Martensitic 9-11%-Cr Steels

Project Number 274

Components subject to long-term creep stress will be made of modern 9-11% chromium steels in future, their characteristics being investigated in several research projects. This project is to broaden and extend knowledge on distortion- and damage characteristics of these steels. With regard to practice-related temperature- and stress areas, a damage model is elaborated that serves development of a service life supervision concept for components made of martensitic steels.

Therefore, the already begun creep tests at single axis- and hollow cylinder samples made of P 91 as well as E 911 are being continued, so that test periods beyond 40,000 h are achieved. Additional random tests at temperatures < 600 °C help to extend the damage models to realistic conditions.

Since light-optical procedures are suitable for component service life assessment in practice only to a limited extent, alternative methods of service life assessment (extension measurement procedure, electron microscope (TEM) investigation at smallest samples, replications and non-destructive testing methods like micro magnetic processes and ultrasonic laminography already developed in other research projects) are to be applied. To this end, continuation of deformation measurements as well as parallel non-destructive testing at real components for validation of the laboratory sample results and numeric simulation for service life calculation is planned.

The results will be included in the VGB guideline TW 507.

The project will be realised from January 1, 2005, to December 31, 2007, and headed by Dr. Karl Maile (Stuttgart Materials Testing Institute) and Dr. Peter Seliger (Siempelkamp Society for Testing and Expertises). It will be mainly financed by means of Forschungsvereinigung der Arbeitsgemeinschaft der Eisen und Metall verarbeitenden Industrie e.V. (AVIF). The project is supported by the Working Group W 12 („Residual Service Life“) of the study group “Heat-resistant Steels”. From the part of VGB, the investigations are supported by the Technical Committee “Materials and Quality Supervision”.