2010 Volume 28 Issue 2 Pages 230-235
Hydrogen embrittlement cracking behaviours of SUS304/Ta/Zr explosive bonded joint during underwater polishing were investigated. Hydrogen embrittlement cracks occurred in the Zr substrate adjacent to the Ta/Zr bond interface during underwater polishing. The open circuit potential of Zr during underwater polishing was drastically reduced immediately after mechanical polishing (within a fraction of a second). The hydrogen yields of Zr-Ta alloys and cold-worked Zr during underwater polishing were estimated from the corrosion current determined by the Tafel extrapolation method. The hydrogen yield increased with a decrease in the Ta content of Zr-Ta alloy, and with an increase in the degree of working (rolling reduction) of Zr. It was deduced that the mechanical grinding in water removing the passive oxide film on the Zr substrate led to the hydrogen absorption into the Zr substrate and the precipitation of zirconium hydrides. Accordingly, hydrogen embrittlement cracks occurred in the deformation layer of Zr around the Ta/Zr bond interface due to the tensile residual stress in the explosive bonded joint.