Design and validation of an in-situ hydrogen embrittlement system in a rotary bending fatigue testing machine

Abstract

Hydrogen is a promising clean energy source, but its integration brings challenges, notably hydrogen embrittlement (HE), which degrades materials used in hydrogen infrastructure. Metals, especially steel, are vulnerable, leading to reduced strength and safety risks. Testing methodologies, including in-situ and ex-situ methods, are crucial to understanding HE. Insitu methods simulate real-time exposure, whereas ex-situ methods focus on post-exposure effects. Rotary bending fatigue tests are particularly interesting as they are cost-effective fatigue machines. This study aims to design and implement an electrochemical cell for in-situ HE testing under cyclic loading in this particular fatigue machine. The study focuses on adapting an electrochemical cell for a rotary bending fatigue machine, testing 42CrMo4 steel. Three key tasks were performed: (i) determining electrochemical parameters for inducing HE through Small Punch Tests (SPTs), (ii) evaluating an electrolyte jet system’s effectiveness, and (iii) designing and validating the electrochemical cell. Electrolytes tested included acid and alkaline solutions, and a novel jetting system was devised to ensure electrolyte coverage during high-speed rotation. The system’s electrical configuration and the cell’s structural adaptations for in-situ hydrogen charging were critical design elements. The tests confirmed the system’s effectiveness in charging the specimen with hydrogen, as evidenced by fatigue life reduction and fracture surface analysis. Specimens precharged with hydrogen, specifically in acidic environments, displayed increased brittleness and premature failure, contrasting with the ductile behavior of non-embrittled specimens. This highlights the system’s potential for future studies on material resistance to hydrogen embrittlement under cyclic loads.