Comparison between an ultrasonic and an electromagnetic metrology for the study of hydrogen embrittlement in steels

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In this work, a comparative investigation is conducted between ultrasonic and electromagnetic non-destructive techniques to assess hydrogen loading in steel specimens. The material studied is a DP800 dual-phase steel, selected for its higher hydrogen uptake capacity compared with other steels. The originality and key contribution of this study lie in the comparison between techniques based on continuous, in-situ measurements performed during the hydrogen loading process and techniques relying on single measurements carried out at the end of the loading, yet capable of reconstructing the entire hydrogen charging trajectory. Hydrogen charging is achieved using an electrochemical method, and the same specimens are used for both measurement approaches. Preliminary ultrasonic measurements reveal an increase in ultrasonic wave velocity of approximately +25 m/s and +50 m/s for two different samples, while preliminary magnetic tests successfully provide loading trajectories for similar thermo-chemical surface treatments.