Influence of physical properties of weld metal on hydrogen diffusion into the heat affected zone of heterogeneous welded joints

The paper presents the analytical solution of one-dimensional problem on hydrogen diffusion in butt heterogeneous welded joints. Such parameters as welded joint thickness, weld thickness, diffusion coefficients, solubilities and initial concentrations of hydrogen in the weld metal and base metal have been taken into account. The effects of microstructure on hydrogen kinetics in homogeneous and heterogeneous welded joints are considered. It is shown that hydrogen concentration in the heat affected zone (HAZ) to a great extent depends on the ratios of the initial concentrations, hydrogen diffusion coefficients and solubilities in the weld metal to those in the base metal. The concentration of hydrogen in the HAZ decreases by three orders of magnitude when welding martensitic steel with austenitic electrodes as compared to homogeneous joints.