Experimental study on slow tensile, fatigue, and impact on X42 steel and #20 carburizing steel

Hydrogen embrittlement is a common phenomenon in high-strength steels and presents a significant challenge in the research and development process. This study aims to analyze the mechanism of hydrogen embrittlement, investigate the causes of crack growth in steel, and conduct experiments at mesoscopic and microscopic scales to gain a deep understanding of the relationship between hydrogen embrittlement and defects in high-strength steels. The research includes a slow tensile test to study the shrinkage and ductility of X42 steel and 20# carburizing steel under air and hydrogen environments. Furthermore, fatigue testing is conducted to comparatively investigate the crack growth of CT specimens in nitrogen and hydrogen environments at different pressures. Additionally, impact testing is performed to examine the fracture of V-notched specimens in air and hydrogen at different pressures. The findings reveal that 20# carburizing steel exhibits better fracture toughness than X42 steel during the slow tensile process, and its hydrogen embrittlement sensitivity is lower. Moreover, the fatigue crack growth process of 20# carburizing steel is less affected by hydrogen embrittlement, resulting in better fatigue rupture resistance compared to X42 steel. Furthermore, the impact toughness value of 20# carburizing steel is higher than that of X42 steel in the impact toughness test. Both steels show varying effects on crack growth under different hydrogenation pressures. Importantly, the impact toughness of both steels is less affected by different hydrogenation pressures.