Application of Fundamental Models for Creep Rupture Prediction of Sanicro 25 (23Cr25NiWCoCu)

Junjing He,Rolf Sandström

doi:10.3390/cryst9120638

Abstract

Creep rupture prediction is always a critical matter for materials serving at high temperatures and stresses for a long time. Empirical models are frequently used to describe creep rupture, but the parameters of the empirical models do not have any physical meanings, and the model cannot reveal the controlling mechanisms during creep rupture. Fundamental models have been proposed where no fitting parameters are involved. Both for ductile and brittle creep rupture, fundamental creep models have been used for the austenitic stainless steel Sanicro 25 (23Cr25NiWCoCu). For ductile creep rupture, the dislocation contribution, solid solution hardening, precipitation hardening, and splitting of dislocations were considered. For brittle creep rupture, creep cavitation models were used taking grain boundary sliding, formation, and growth of creep cavities into account. All parameters in the models have been well defined and no fitting is involved. MatCalc was used for the calculation of the evolution of precipitates. Some physical parameters were obtained with first-principles methods. By combining the ductile and brittle creep rupture models, the final creep rupture prediction was made for Sanicro 25. The modeling results can predict the experiments at long-term creep exposure times in a reasonable way.

Highlights

The concept of Advanced Ultra-supercritical (AUSC) power plants has been proposed world-wide in order to raise the operating temperature and stress for fossil-fired power plants [1].Thereby, the efficiency of the power plants can be improved and the CO2 emissions can be reduced.In the AUSC conditions, the temperature is 700 ◦ C or more and the stress is above 30 MPa, which imposes high requirements on the materials used for power plants
The fundamental models shown here are based on the microstructure and defect evolution, fundamental modelshave shown here aredefined based on defect evolution, where The all involved parameters been well andthe nomicrostructure parameters areand fitted to the creep where all involved parameters have been well defined and no parameters are fitted to the creep rate
Creep rupture strength of Sanicro 25 has been predicted with the help of fundamental creep models

Summary

Introduction

In the AUSC conditions, the temperature is 700 ◦ C or more and the stress is above 30 MPa, which imposes high requirements on the materials used for power plants. Austenitic stainless steels and nickel-based superalloys are candidate materials for the critical components serving at high temperature and stress. Sanicro 25 (23Cr25NiWCoCu, called UNS S31035) is an austenitic stainless steel developed by Sandvik [2,3,4,5] and is designed for use in steam boilers at high temperatures. The high temperatures and stresses give rise to a slow mechanical deformation that is called creep, which will eventually result in rupture. This type of deformation is life controlling for many components in fossil-fired power plants

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Discussion

Conclusion