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 mu m to 500 mu m, 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 gamma- and delta-hydrides present a crack-free surface while the saturated hydrogen absorption samples which consist of epsilon-hydride exhibit not only large cracks but also bulges on the surface. The hydride decomposition temperatures of epsilon -> delta and delta -> alpha during dehydriding are determined to be about 600 degrees C and 700 degrees 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. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.