Hydrogen Embrittlement in Nickel-Base Superalloy 718

Material Challenges and Hydrogen Embrittlement Assessment for Hydrogen Utilisation in Industrial Scale

“…Hydrogen interaction causes a solid-solution strengthening effect similar to that of carbon or nitrogen. This introduces resistance to the gliding or movement of dislocations [30]. Hydrogen damage manifests as hydrogen-induced blistering, cracking due to precipitation of hydrogen in the internal lattice, hydrogen attacking, and cracking due to hydride formation [28].…”

“…In situ charging can be achieved via a range of different techniques that are mechanically comparable. Cathodic charging can result in an apparent loss in tensile strength relative to other charging techniques, but this loss is small compared with the loss in ductility and fracture toughness as a result of HE [30].…”

“…The rate is dependent on the applied temperature and pressure, which can result in the need for more complicated systems to address safety risks. Additionally, it can be difficult to expose samples to adequate concentrations of hydrogen given that sorption and diffusion can be slow in the absence of high temperatures and pressures [30].…”

“…When low current densities are applied to the sample, hydrogen adsorbs onto the metal as a function of current density, allowing only the depth of diffusivity to be calculated [30]. Harsh electrochemical charging, however, may decrease tensile strength due to the induction of subsurface and surface cracking during the charging process.…”

“…High hydrogen concentration gradients that arise at high current densities result in internal stress, which in turn increases embrittlement and loss of strength. To reduce these effects, low current densities can be used for longer charging times [30]. Additionally, when using acidic aqueous media to facilitate the generation of hydrogen at the cathode/sample surface, the presence of H 2 S can result in the precipitation of hydrogen bubbles within cracks.…”