Hydrogen absorption cracking of zirconium alloy in the application of nuclear industry

The hydrogen absorption cracking behavior of Zr-4 has been investigated based on the microstructure, hydrogen absorption amount as well as residual stress. The results show that the grain size has a pronounced effect on the hydrogen absorption cracking, with the increase of grain size from 30 μm to 500 μm, the cracks vary from small cracks of independence to large cracks that connect with each other along the radial direction. The unsaturated hydrogen absorption samples which consist of γ- and δ-hydrides present a crack-free surface while the saturated hydrogen absorption samples which consist of ɛ-hydride exhibit not only large cracks but also bulges on the surface. The hydride decomposition temperatures of ɛ → δ and δ → α during dehydriding are determined to be about 600 °C and 700 °C respectively. In the unsaturated hydrogen absorption samples, both the thickness expansion and radial residual stress present a positive liner correlation with the hydrogen absorption amount. Based on the experimental results a mechanism of hydrogen absorption cracking is proposed in zirconium alloys.