On the suitability of slow strain rate tensile testing for assessing hydrogen embrittlement susceptibility

TL;DR

This paper evaluates the effectiveness of slow strain rate tensile testing in assessing hydrogen embrittlement, revealing that hydrogen diffusion alone cannot explain observed fractures and highlighting the importance of sub-critical crack growth.

Contribution

It introduces a combined experimental and modeling approach to analyze crack growth during SSRT and questions the reliability of SSRT metrics for hydrogen embrittlement assessment.

Findings

Hydrogen diffusion alone does not account for intergranular fracture depths.

Crack initiation can occur at as low as 40% of the time to failure.

Sub-critical crack growth influences SSRT interpretation.

Abstract

The onset of sub-critical crack growth during slow strain rate tensile testing (SSRT) is assessed through a combined experimental and modeling approach. A systematic comparison of the extent of intergranular fracture and expected hydrogen ingress suggests that hydrogen diffusion alone is insufficient to explain the intergranular fracture depths observed after SSRT experiments in a Ni-Cu superalloy. Simulations of these experiments using a new phase field formulation indicate that crack initiation occurs as low as 40% of the time to failure. The implications of such sub-critical crack growth on the validity and interpretation of SSRT metrics are then explored.