Operando cryogenic processing effects on residual stress and magnetism of martensitic stainless steel for energy sector

Martensitic stainless steels (MSS) are widely used in the energy sector due to their high hardenability, corrosion resistance, and favourable mechanical properties. Their performance in extreme environments—such as fusion reactors, offshore systems, and hydrogen infrastructure—depends strongly on the interplay between microstructure, residual stresses, and resulting properties, including magnetic behaviour and mechanical strength. In fusion applications, neutron irradiation and high magnetic fields can significantly alter MSS microstructure, potentially compromising material stability and leading to component failure. To enhance microstructural stability under such conditions, advanced processing methods are required. Cryogenic processing (CP), which involves exposing materials to temperatures below 77 K, has shown promise in improving properties like hardness and corrosion resistance through microstructural refinement. However, the underlying mechanisms governing these improvements, particularly in MSS for energy applications, remain insufficiently understood. Existing studies indicate that CP can influence magnetic properties and residual stresses, but comprehensive operando investigations, especially under strong magnetic fields, are lacking. This study investigates the effects of CP on MSS EN X17CrNi16-2 under different treatment conditions, including conventional heat treatment, CP, and CP combined with magnetic field exposure up to 5 T. The work examines micro-residual stresses ( ex-situ and in-situ ), magnetic behaviour using advanced microscopy techniques, and mechanical properties via microhardness testing. Additionally, it provides novel insights into the time-dependent mechanisms of CP through advanced neutron measurements, contributing to a deeper understanding of structure–property relationships in MSS for future energy applications.