Mo元素对临氢工况奥氏体不锈钢敏化行为的影响OA

Catalytic cracking units and hydrogen energy equipment frequently operate at intermediate temperatures,where austenitic stainless steels are prone to sensitization.To clarify how molybdenum governs this behavior and to support material selection and remaining-life evaluation of pressure-bearing parts,two grades are examined:Mo-free S30408 and S31608 grade containing approximately 2%Mo(weight).Both steels are held at 650℃for a series of soaking times to induce sensitization.Their microstructural changes,degree of sensitization(DOS),and loss of mechanical performance are assessed using optical metallography,double-loop electrochemical potentiodynamic reactivation(DL-EPR)measurements,and tensile and impact testing.As the holding time increases,M23C6 carbides precipitate along the grain boundaries of both steels and gradually become more continuous,which widens the chromium-depleted regions and increases the tendency toward intergranular corrosion.The Mo-bearing S31608,however,shows slower carbide precipitation,and its DOS increases far less steeply than that of S30408.This behavior indicates that Mo improves the chemical stability near the grain boundaries,partly offsetting the sensitization-driven degradation and improving service reliability under high-temperature,hydrogen-bearing conditions.This study offers experimental support for the long-term safe operation of petrochemical and hydrogen energy facilities,refined material selection,and service life prediction,while also bearing practical value in limiting medium leakage and energy losses arising from material failure.