Long-term creep behaviours and structural stabilities of austenitic heat-resistant stainless steels

ABSTRACT

For heat resistant alloys, long-term structural stability at high temperatures is a critical issue for alloy design and applications. In this paper, the long-term creep behaviours and structural stabilities of six heat resistant high Ni alloys and austenitic stainless steels have been studied. The longest creep rupture life is up to 359 283 hours. High Ni and Cr alloys show a good combination of high creep and oxidation resistances. Precipitation of nano MX particles with a very low growth rate improves long-term creep resistance at high temperatures. Long-term stable multiple nanoprecipitates of MX, Cu-rich, Laves and M23C6 phases can greatly contribute to the creep strength. Low Ni austenitic stainless steels show comparatively low oxidation and creep resistances. It was first found that at 800°C, Cr2N could form in the low Ni steel with a long-term crept by the absorption of nitrogen from the air into the matrix.

KEYWORDS:

• Creep
• austenitic stainless steel
• Ni based alloy
• structural stability
• microstructure

Acknowledgments

This paper is published by permission of Alleima EMEA AB. The supports of Dr Tom Eriksson and Mr Martin Östlund are greatly acknowledged.

Disclosure statement

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