|
|
ICFRM-12 Santa
Barbara, 4-9 December 2005
Abstract
A comprising steady-state creep model for the austenitic AISI 316 L(N) steel
Michael Rieth
Forschungszentrum
Karlsruhe, Institut für Materialforschung I, Karlsruhe, Germany
Among many other
applications the 17Cr12Ni2Mo steel 316 L(N) is envisaged for ITER applications.
Since creep data allowing statements to be made about the stress dependence of steady-state
creep rate had been almost unavailable, a special long-term creep testing
program at 550 °C and 600 °C was started in 1991. After an experimental
period of about 10 years the creep tests have been either finished or aborted,
and evaluated. Now this low-stress creep data not only allow for a much better
long-term prediction of the reliability of 316 L(N) applications but also
enable deformation modeling for a broader stress range.
The present work focuses
mainly on the set-up of a steady-state creep model with help of rate-equations
well known for different deformation mechanisms, such as diffusional flow,
dislocation climb, and dislocation glide. In addition, the impact of
microstructure and precipitation formation on steady-state creep
is outlined and discussed. The resulting creep model consists of a summation of
contributions for diffusion creep, power-law creep, and power-law breakdown
(transition to pure dislocation glide). Most model parameters are either known
material constants or could be directly deduced from the available data while a
few free parameters had to be adjusted to the experiments. As a result, the
creep model agrees well with experimental data for temperatures between
550 °C and 750 °C and for shear stresses down to 30 MPa. For
very low stresses the model predicts far higher creep rates as usually
extrapolated from tests performed at the medium stress range.
249 words (max. 250 words)
Corresponding Author: Dr.
Michael Rieth
Forschungszentrum
Karlsruhe, IMF-I
Hermann-von-Helmholtz-Platz
1
76344
Eggenstein-Leopoldshafen, Germany
P.O.
Box 3640, 76021 Karlsruhe, Germany
Tel. +49 7247 82 2909, Fax +49 7247 82 4567
michael.rieth@imf.fzk.de