THE OXIDATION AND CORROSION OF ZIRCONIUM AND ITS ALLOYS XIIInSome observations of hydride in zirconium and zircaloy-2 and its subsequent effect on corrosion

摘要

An examination of hydride platelets in zirconium and zircaloy-2 by autoradiography and electron-microscopy has shown that normal metallographic techniques provide a satisfactory method for identifying hydride in these materials. The standard methods do not give a good estimate of the size (particularly the thickness) of hydride platelets. Our studies have shown that the hydride platelets are very thin (500-1000A) and that the greater apparent thickness of them, when observed metallographically, results from etching out of the hydride together with some of the surrounding metal.nNo positive correlation was established between the presence of hydride at the oxide/metal interface and breakdown of the oxide film during the oxidation of either zirconium or zircaloy-2. The cracking of the oxide which is associated with the sites of hydride particles is apparently mechanical in nature.