Ultrasonic nanocrystal surface modification effect on reduction of hydrogen embrittlement in Inconel-625 parts fabricated via additive manufacturing process

Abstract

With its considerable design flexibility, additive manufacturing, especially laser powder based fusion (PBF-LB) has been considered a possible method for fabricating metal parts needed in the hydrogen sector. However, hydrogen embrittlement of additively manufactured components is one of the essential issues that must be resolved before the practical application in the hydrogen industry. This study evaluates the effect of ultrasonic nanocrystal surface modification (UNSM) treatment on reducing hydrogen embrittlement in additively manufactured Inconel-625 alloy. The slow strain rate tensile test results of specimens with or without UNSM-treatment that were charged hydrogen gas at a high pressure of 700 bar for two weeks, it was confirmed that the elongation reduction decreased by about 6.3 % in the case of the UNSM-treated specimen. Even though the hydrogen concentration doubled after the UNSM-treatment, the decrease in elongation reduction indicates that the UNSM-treatment is effective in reducing hydrogen embrittlement. In addition, hardness, and microstructural inspection were employed to validate the mechanism of preventing hydrogen penetration after UNSM-treatment.