Hydrogen Evolution Measurements for a Martensitic-Austenitic Weld Metal

Hydrogen evolutions for martensitic-austenitic weld metals were measured at 45 °C. The specimen without the austenite released hydrogen in about two days, and this result agrees with the 72 h holding time required by JIS Z3118. In the case of the specimens that contain the retained austenite, hydrogen release continued for about 100 days or more. We derived the analytic solution of the McNabb & Foster diffusion equation by regarding the austenitic microstructures as trapping sites to compare the experimental and calculation results, and showed that both of them are in good agreement. We also showed that the initial ratio of free and trapped hydrogen atoms is not necessarily equal to the thermal equilibrium condition at the measurement temperature, which can be analysed using the present solution.