12Cr2Mo1R(H) steel is commonly used to make hot-wall hydrogenation reactors given its excellent mechanical properties and hydrogen embrittlement (HE) resistance. Longtime exposure to high-pressure hydrogen at medium temperature would still severely damage the mechanical properties of the Cr-Mo steel with surface HICs caused by hydrogen adsorption and hydrogen uptake. The mechanisms of HE remain controversial and have not been fully understood so far.
The HE of the steel was investigated by slow strain rate test at different strain rates with in situ hydrogen charging. The diffusion coefficient of hydrogen in the steel is measured by electrochemical technology of hydrogen permeation. HIC cracks of the fractured specimens were captured with field emission SEM equipped with an electron backscatter diffraction system.
Results showed that the hydrogen led to the plasticity of the samples reduced significantly, together with the distinct work hardening behavior induced by hydrogen charging during plastic flow stage. The fracture of in situ charged sample changes from quasi-cleavage to intergranular fracture with the decreasing of strain rates, which indicates that the steel become more susceptible to hydrogen. High densities of dislocations and deformation are found around the crack, where grains are highly sensitive to HIC. Grains with different Taylor factor are more susceptible to intergranular crack.
The results of the study would be helpful to a safer application of the steel.
The research is supported by the State Key Laboratory of Metal Materials for Marine Equipment and Application, Science & Technology Support Program of Sichuan Province (2016GZ0271), Natural Science Foundation of Shandong Province (ZR2017MEM019) and National Natural Science Foundation of China (51201144).
Zhang, K., Fan, Y., Luo, X., Chen, X., Ban, C., Zhao, H. and Chen, Y. (2019), "The study of hydrogen embrittlement of 12Cr2Mo1R(H) steel by slow strain rate test with
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