Structural integrity and impact toughness of austenitic stainless steels

摘要

Next generation biomass power plants must sustain increased efficiency, based on high-temperature operating conditions, in order to satisfy the increasing global energy consumption. The structural integrity of the materials used for critical components, such as the superheater, in the future biomass power plants are crucial for safety considerations due to the new operating conditions. Thus, the used materials must have improved high-temperature corrosion resistance and a sufficiently maintained toughness. This study is concerned with how long term high-temperature ageing influence the impact toughness of three commercial austenitic stainless steels, namely AISI 304, AISI 310M and Sanicro 31HT. AISI 304H and AISI 310M showed a steep decrease in impact toughness when increasing ageing temperature and time, up to 700°C and 30 000 hours. However, Sanicro 31HT showed relatively high impact toughness even after 30 000 hours ageing at 700°C. Scanning electron microscopy was used to analyse the influence of ageing on the microstructure and discuss the difference in impact toughness between the alloys in terms of the influence of ageing on failure mechanisms.