Basic creep models for 25Cr20NiNbN austenitic stainless steels

Abstract

Basic models for solid solution and precipitation hardening during creep are presented for the austenitic stainless steels 25Cr20NiNbN (TP310HNbN, HR3C, DMV310N). The solid solution hardening is a result of the formation of Cottrell clouds of solutes around the dislocations. In addition to slowing down the creep, the solutes increase the activation energy for creep. The increase in activation energy corresponds to the maximum binding energy between the solutes and the dislocations. The formation of fine niobium nitrides during service enhances the creep strength. It is found that the nitrides have an exponential size distribution. In the modelling the critical event is the time it takes for a dislocation to climb over a particle. The creep models can accurately describe the observed time and temperature dependence of the creep rupture strength.

Keywords:

• Austenitic stainless
• Elevated temperature
• Precipitation
• Solid solution hardening

Financial support through by the European Union (directorate-general for energy), within the project MACPLUS (ENER/FP7EN/249809/MACPLUS) in the framework of the Clean Coal Technologies is gratefully acknowledged.

Notes

This paper is part of a special issue on Energy Materials