Modelling of Hydrogen Diffusion in a Weld Cold Cracking Test: Part 1, Experimental Determinations of Apparent Diffusion Coefficient and Boundary Condition

Abstract

Weld cold cracking is a kind of hydrogen embrittlement and is a serious problem when high strength steel is concerned. Cold cracking usually occurs at the area where hydrogen locally accumulates, and hence hydrogen diffusion modelling is important to understand the hydrogen distribution in a welded joint. In this paper, we conducted the permeation tests to measure the apparent diffusion coefficients of hydrogen with varying the hardness and the plastic strain of the steel. The experimental results were used to develop the empirical equation to predict the diffusion coefficient. The empirical equation is described as a function of temperature, hardness and plastic strain. Next, we measured the evolution curves of hydrogen released from the rectangular specimens. We considered the boundary condition of the surface exposed to the atmosphere, and the experimental results were used to determine the boundary condition. The empirical equation and the boundary condition obtained in this paper will be used for the numerical calculations of hydrogen diffusion in a weld cold cracking test in the companion paper.