Criteria for hydrogen-assisted crack initiation in Ni-based superalloy 718

The tensile mechanical properties of a Ni-based superalloy 718 uniformly precharged with approximate to 90 mass ppm hydrogen were investigated under a wide range of temperatures to shed light on the long-standing uncertainties surrounding the H-related embrittlement mechanisms of the material. The detrimental effect of H on ductility was found to be substantial in the near-ambient to high-temperature range, up to 300 degrees C, stemming from H-assisted microcrack initiations along annealing twin boundaries (ATBs) and crystallographic slip planes (SPs). Dynamic H-dislocation interaction, which has been thought to be a prerequisite for the onset of embrittlement, was found to be unimportant, as demonstrated by employing supplemental tests that incorporated prestraining and intermediate temperature changes. By combining the insights gained from the successfully designed test program, a new model for the nucleation process of H-induced fracturing was established.(c) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study investigated the tensile mechanical properties of a Ni-based superalloy 718 precharged with approximately 90 mass ppm hydrogen under a wide range of temperatures, aiming to clarify the uncertainties surrounding the hydrogen-related embrittlement mechanisms of the material. The study found that hydrogen had a substantial detrimental effect on the ductility of the material in the near-ambient to high-temperature range, resulting from microcrack initiations along annealing twin boundaries and crystallographic slip planes. Additionally, the study revealed that the dynamic hydrogen-dislocation interaction was not important for embrittlement. By combining the insights gained from the test program, a new model for the nucleation process of hydrogen-induced fracturing was established.