Their results show a reduction of the decomposition peak intensity, which is linked to the extent of the phase separation, of up to 60 %. This shows potential for the implementation of alternative processing routes to prolong the lifetime of components in service.
Stainless steels, which contain more than 11% chromium to create a self-healing layer, are an increasingly important class of engineering materials and used in a broad range of applications. Duplex stainless steels combine the advantageous properties of two phases of iron: ferrite, which is body centered cubic and austenite, which is face centered cubic. This gives the material, for example, improved strength and stress-corrosion resistance compared to conventional austenitic grades.
These steels are used in highly corrosive environments under high stress and temperatures. They contain more than 20% chromium, which causes the alloys to become brittle during service if exposed to temperatures above 300°C for a prolonged period of time. This is due to the immiscibility of iron and chromium in the ferrite phase at lower temperatures leading to phase separation.
Extending the service life of such alloys is important from both a cost perspective and from an environmental point of view.
Working with ISIS scientist Tristan Youngs, the team from KTH Royal Institute of Technology in Stockholm, Sweden, studied the duplex stainless steel alloy 2507 in situ during accelerated service conditions in a furnace. The penetration of neutrons into the sample and their unique interaction with the elements present enabled them to probe the phase separation as it occurred.
“During this accelerated aging we could follow how the phase separation progressed depending on the heat treatment condition used prior to aging," explains Monika Rolinska from KTH Royal Institute of Technology.
“We could show that some proposed heat treatments reduce the extent of the phase separation by up to 60 % during accelerated aging. This implies that the service life of components could be extended significantly by applying tailored heat treatments."
Read the full paper here: https://doi.org/10.1007/s11661-025-07906-1
