The contribution of Cr and Ni to hydrogen absorption energy in Fe-Cr-Ni austenitic systems: A first-principles study

The present study focuses on a novel hydrogen-improved strength-ductility balance in several practical Fe-Cr-Nibased austenitic alloys that directly depends on the dissolved hydrogen content. The hydrogen absorption energy of Fe-Cr-Ni model alloys that have a face-centered cubic structure was examined using first-principles calculations to verify the contribution of Cr and Ni substitutions from Fe to hydrogen solubility in these alloys. Chromium substitution reduced the hydrogen absorption energy to a substantially greater degree than does Ni substitution, with increased Cr: Ni ratios resulting in higher hydrogen solubility. This pattern seen in the calculations supports the previously obtained experimental results in practical alloys with various Cr: Ni ratios. The pronounced reduction in hydrogen absorption energy that results from Cr substitution was mostly attributed to a decrement in the chemical effect derived from the electronic binding state rather than a mechanical effect caused by changed interatomic spacing due to these substitutions. We propose here a Cr-equivalent index to predict hydrogen solubility in Fe-Cr-Ni-based alloys that have varying Cr and Ni content.