Effect of post-GBE strain-sensitisation on corrosion resistance of grain boundary engineered 304 austenitic stainless steel

Abstract

Control of grain boundary microstructure for grain boundary engineering (GBE) is effective to prevent intergranular corrosion by disconnection of corrosive random boundary network resulting from the introduction of coincidence site lattice boundaries during the frequent formation of annealing twins in bulk austenitic stainless steels. Since the practical use of austenitic stainless steels often includes straining and heating processes, such as forming, annealing and welding, the processes after the GBE treatment could degrade the optimised grain boundary microstructure and the high corrosion resistance of grain boundary engineered (GBEed) austenitic stainless steels. Therefore the present study examined the effects of post-GBE strain-sensitisation on grain boundary microstructure and corrosion resistance of a GBEed 304 austenitic stainless steel produced by a single-step thermomechanical processing for GBE. The results showed that the grain boundary microstructure was changed apparently and the corrosion resistance gradually decreased in the GBEed steel with an increase in post-GBE strain followed by sensitisation, but the GBEed steel maintained significantly higher corrosion resistance during the post-GBE strain-sensitisation than the equivalently strain-sensitised base steel.

Keywords:

• grain boundary engineering
• stainless steel
• corrosion
• EBSD
• strain
• annealing

Acknowledgements

This work was supported by a Grant-in-Aid for Scientific Research (A) (No. 24246117), a Grant-in-Aid for Science Research (S) (No. 19106013), and a grant from the Global COE Program ‘Materials Integration (International Center of Education and Research), Tohoku University,’ and partially entrusted by MEXT, Japan. The authors are grateful to Professor T. Watanabe for his useful comments. They also wish to thank Mr T. Oyamada, Mr K. Kurihara and Mr A. Honda for their useful discussions and technical assistance.

Notes

The authors wish to submit this paper for a special issue ‘Celebrating the Career of J. Thibault-Penisson’. Control of grain boundary microstructure for grain boundary engineering (GBE) is effective to prevent intergranular corrosion of austenitic stainless steel, but the effect of post-GBE strain-sensitisation on the grain boundary microstructure and corrosion has not been clarified. This work examined the effect of post-GBE strain-sensitisation on intergranular corrosion in the GBEed austenitic stainless steel. The results showed that the corrosion resistance gradually decreased in the GBEed steel with an increase in post-GBE strain followed by sensitisation, but the GBEed steel maintained significantly higher corrosion resistance during the post-GBE strain-sensitisation than the equivalently strain-sensitised base steel.