Investigating the effects of hydrogen trapping on hydrogen environment-assisted cracking of vanadium-added steels

•Impact of hydrogen trapping on HEAC in vanadium-added steels investigated.•Larger trapping capacity does not always correlate with increased HEAC resistance.•Hydrogen trapping effectiveness in reducing HEAC depends on hydrogen concentration.•In HEDE-dominated fracture, hydrogen trapping does not mitigate HEAC susceptibility. Current standards and technical specifications typically limit the maximum hardness of steels under subsea cathodic protection. However, hydrogen trapping has recently gained attention for mitigating hydrogen embrittlement. This study investigates the potential of hydrogen trapping to enhance hydrogen environment-assisted cracking (HEAC) resistance of vanadium-added steels under cathodic protection conditions. The investigation includes nano/microstructural characterization, electrochemical hydrogen permeation, and thermal desorption analyses. HEAC resistance is evaluated through fracture toughness tests under cathodic polarization. AISI4330 V steel is evaluated at both acceptable and higher hardness levels than those allowed by current standards. Additionally, a modified version of a similar steel designed to enhance hydrogen trapping is studied. Hydrogen trapping is mainly related to the presence of carbides in each alloy. Even though the types and characteristics of carbides differ among steels, the de-trapping activation energy is not significantly altered. Instead, the primary factor influencing the hydrogen trapping behavior is the density of traps. Although steels with hardness levels higher than accepted standards exhibited larger trapping capacity, it does not necessarily result in enhanced the HEAC resistance. For the materials considered here, fracture toughness is not enhanced by a higher trapping capacity when materials with similar hardness level are tested under cathodic protection conditions at –1,100mVSCE. At this potential, HELP + HEDE mechanisms are evident for the lower hardness condition, while HEDE mechanism is observed for the higher hardness level. Nevertheless, at less negative potentials (−900 and –780mVSCE), the steel trapping ability can account for increased HEAC resistance and a transition from HEDE to HELP + HEDE mechanisms.