Quantifying Void Formation and Changes to Microstructure During Hydrogen Charging: A Precursor to Embrittlement and Blistering

Hydrogen diffusion into the microstructure is a key first step for both hydrogen embrittlement and hydrogen blistering. Previous research has suggested that an increase in voids pre-loading can significantly affect the void growth and failure of samples during loading. However, there is a lack of knowledge on the effect of hydrogen alone on initial void fraction. Therefore, the microstructures of six samples of 13 pct chromium stainless steel were imaged using a computed tomography technique before and after hydrogen charging. These images were then formed into a 3D model to quantify the total void volume fraction before and after charging. Overall, charging was shown to increase void fraction by 18 times. This work provides support to the theory that an important role of hydrogen in promoting failure is to increase void production through recombination into H₂.