Structural-phase transformations and evolution of defect structure under thermal influence and hydrogenation of Cr-coated E110 zirconium alloy: Experimental research and first-principal calculations

Abstract

This work is aimed at studying the peculiarities of structural-phase transformations and defect structure evolution in samples of Zr1%Nb zirconium alloy with and without chromium coating. As a result of ex situ and in situ study of thermal and hydrogen impact processes, it was found that chromium coating on zirconium alloy Zr1%Nb contributes to the reduction of hydrogen absorption rate, which is 1.8 less compared to the material without protective coating. It is established that in the process of hydrogenation of zirconium alloy with chromium coating hydrogen diffuses into the volume of the material and is evenly distributed through the thickness of the sample which indicates the excellent protective qualities of this coating. A gradient of hydrogen distribution is observed in the volume of material without chromium coating after hydrogenation. It has been shown that the increase in hydrogen resistance of zirconium alloy with chromium coatings is in additional due to the presence of an incoherent interface and defects in its vicinity. Positron spectroscopy has shown that, in the case of chromium-coated zirconium materials after thermal treatment and hydrogenation, hydrogen is mainly localized at the Zr/Cr interface. Ex situ methods have determined that thermal and hydrogen impact results in the accumulation of dislocation-type defects in zirconium alloy due to the formation of hydrides.