Quantitative physical modeling of the effect of precipitates in the subgrain interior on the creep curve and service life of P91

ABSTRACT

This work deals with a physically based creep model of the martensitic 9% Cr-steel P91. In particular, we quantitatively study the effect of precipitates located in the subgrain interior on the creep curve and the lifetime of the material. Our creep model is capable of simulating the microstructural evolution parallel to creep curves and has been further developed towards predicting time-to-rupture (TTR) diagrams. We demonstrate how the number density, size and shape of the precipitates in the subgrain interior affect the creep curve and thus the lifetime of the material. Three according parameter studies on the material P91 compare microstructures with/without precipitates and/or assuming specific shapes by introducing aspect ratios. These simulations can be used as a basis for further development of materials with regard to the precipitation phases.

KEYWORDS:

• Creep
• martensitic 9-12% Cr-steel
• P91
• modelling
• dislocation creep
• dislocation climb
• precipitates
• microstructure

Acknowledgments

L.W., F.R, G.Z & B.S. gratefully acknowledge funding from Austrian Science Fund (FWF) within the project P-31374 “Software Development on Dislocation Creep in Alloys”. Furthermore, L.W. would like to thank the Linz Institute of Technology (LIT), the province of Upper Austria and the Federal Ministry of Austria – Education, Science and Research (BMBWF) for financial support within the project LIT-2021-10-SEED-115,01/899978 “MLSC - Model Development for Lifetime Assessment of Steels under Various Creep Loads”. J.M. gratefully acknowledge student funding from Johannes Kepler University (JKU) Linz. Financial support from Siemens Energy Global GmbH & Co. KG is gratefully acknowledged. The authors want to thank Dr Torsten Neddemeyer & Dr Torsten-Ulf Kern from Siemens Energy Global GmbH & Co. KG and Prof. Dr John Hald from DTU (Technical University of Denmark) for fruitful discussions.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Contributor Roles Taxonomy (CRediT) author contributions

L. Witzmann (L.W.): conceptualisation, methodology, validation, formal analysis, data curation, writing – original draft, visualisation; J. Mergl (J.M.): methodology, software, data curation; F. Riedlsperger (F.R.): conceptualisation, data curation, writing – original draft, writing – review & editing; B. Krenmayr (B.K.): investigation, visualisation; G. Zuderstorfer (G.Z.): software; B. Sonderegger (B.S.): conceptualisation, methodology, formal analysis, resources, writing – original draft, writing – review & editing, supervision, project administration, funding acquisition

Additional information

Funding

This research was funded in whole or in part by the Austrian Science Fund (FWF) [P-31374]. Further the work was supported by the Linz Institute of Technology (LIT), the province of Upper Austria and the Federal Ministry of Austria – Education, Science and Research (BMBWF) [LIT-2021-10-SEED-115,01/899978]; Johannes Kepler University (JKU) Linz [Student funding].