Cathodic hydrogen charging of Inconel 718

The nickel based superalloy IN718 is known to be prone to hydrogen sensitivity, causing degradation of its mechanical properties. Therefore, during mechanical testing of hydrogen charged samples, a well-defined hydrogen distribution is essential to better understand the influence of hydrogen on dislocation movement and plasticity behavior. The possibility of charging cylindrical specimens of IN718 with hydrogen using cathodic charging is investigated. The method is based on an electro-chemical process using a molten salt electrolyte. The resulting hydrogen concentration is measured for various radii, and it is shown that the anisotropic diffusion coefficient resulting from electromigration, inherent in the charging method, must be taken into account as it has a major impact on the charging parameters of IN718. Also, no evidence of degassing during storage is found. Further, changes in surface roughness were examined by SEM, and only limited surface degradation is observed, which is not considered to significantly affect the results.