2010 Volume 28 Issue 2 Pages 216-221
In order to clarify the behaviour and mechanism of the hydrogen embrittlement in SUS304ULC/Ta/Zr explosive bonded joint, the hydrogen embrittlement cracking at Ta/Zr bond interface was characterised. Cracks occurred in the Zr substrate along the wavy interface of the hydrogen-charged Ta/Zr joint. The cracking susceptibility increased drastically when the potential of specimen during hydrogen-charging was reduced below the redox potential of hydrogen. γ-ZrH and δ-ZrH were precipitated in the hydrogen-charged Zr and the precipitated γ-ZrH possessed a (0002)α-Zr//(11-1)γ-ZrH, [21-1-0]α-Zr//γ-ZrH crystallographic relationship. An in-situ observation of the hydrogen embrittlement cracking with SEM and TEM revealed that cracks were initiated in zirconium hydrides and propagated preferentially along zirconium hydrides. These results suggested that the hydrogen embrittlement mechanism of the Zr base metal was caused by the precipitation of zirconium hydrides and the brittle fracture of them.