X-rays reveal duplex embrittlement resistance
11 March 2021
Researchers from Sandvik and the Royal Institute of Technology (KTH) in Stockholm used high-energy X-rays at the Swedish Material Science beamline to find out why its steels are more resistant to hydrogen embrittlement than its competitors’. It was possible to see what was happening within the steel structure in real-time, in environments that mimic how the steel is used.
The explanation emerged in one of the first uses of the Swedish Material Science beamline in 2019. At the beamline, high-energy X-rays can penetrate steels, enabling researchers to map the hydrogen-induced changes in structure within steels – and how those structural changes vary over time – in environments that mimic how the steel is used.
Researchers from Sandvik and KTH exposed the steel samples to hydrogen and placed these steels under stress – and studied how hydrogen rapidly moves within and interacts with the steel, as well as how the steel’s internal structure evolved. Duplex stainless steels consist of two phases: the body-centered-cubic (bcc) phase and the face-centered-cubic (fcc) phase. Both fcc and bcc phases are distributed in a complex pattern within the steels. Measurements showed that hydrogen could quickly enter the duplex steel but causes different changes in the two phases.
The fact that these phases interact so differently with hydrogen is important: the boundary regions between the two phases accommodate more hydrogen and can withstand more internal stress. The coordinated response of the two phases hinders the initiation of micro-cracks, thus providing high resistance to embrittlement.
The experiments were the first time that these hydrogen-microstructure interactions were observed in real-time. The results showed that with their finer microstructure, Sandvik duplex steels are significantly more resistant to embrittlement than competitor steels.
You can find more news in the news archive.