Hydrogen permeation and embrittlement susceptibility of X80 welded joint under high-pressure coal gas environment

• An electrochemical hydrogen permeation device was designed for high pressure gases.
• The sensitivity of CGHAZ to HE is the highest in welded joints.
• HE sensitivity depends on material microstructure and hydrogen permeation behavior.

Hydrogen permeation and slow strain rate tests in a high-pressure hydrogen-containing coal gas, combined with microstructural analysis, were conducted on X80 base metal, weld metal, and coarse-grained heat-affected zone (CGHAZ). Variation in the calculated diffusivity from high to low was in the following sequence: CGHAZ, weld metal, and base metal. This result was contrary to those of sub-surface hydrogen concentration and hydrogen embrittlement susceptibility. Hydrogen permeation in CGHAZ decreased the cross-sectional shrinkage by 34.56%, which indicates susceptibility to hydrogen embrittlement. The co-effects of microstructure, hydrogen diffusivity, and concentration were the main factors that influenced hydrogen embrittlement susceptibility.