High temperature hydrogen attack is a damage mechanism that threatens the integrity of critical steel components in petrochemical plants and refineries when the hydrogen diffuses into the steel and reacts with the carbides within to produce pores containing methane. With the motivation of understanding the role of carbide stability on the reaction with hydrogen, samples of a classic 2.25Cr-1Mo steel were subjected to a variety of heat treatments that generate a variety of carbides, prior to exposure to high-pressure hydrogen in an autoclave. Using quantitative carbide and microstructural characterisation, it has been possible to demonstrate the roles of four variables: (a) the non-equilibrium chemical composition of carbide; (b) the fraction of the carbide that is closest to the thermodynamic equilibrium state; (c) the location of where the depletion preferentially occurs.

Subject
Materials, Carbides, Tempering temperature, Hydrogen attack, Methane, Steel, Carbon, Risk reduction, Tempering, Heat treatment, Voids, Hydrogen, Inclusions
Keywords:
hydrogen attack, carbides, synchrotron diffraction, tempering, non- equilibrium
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2023
Association for Materials Protection and Performance (AMPP)
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