MECHANICAL AND CHEMICAL FAILURE OF CERMET IN OXIDATIVE MEDIUM

摘要

The connection between chemical and mechanical failure under high - temperature oxidation of nuclear cermet composition (CC) with easy-oxidizing sphere inclusions of uranium dioxide and heat-resistant matrix was studied. It was shown that local stresses in the matrix caused by thermo-chemical expansion of inclusions define the sequence of phase transformations in the nickel-chromium alloy. That causes its periodical cracking. The crack size and the propagation speed depend of the volume of oxidation products, molar value changes, the rate of dioxide uranium reaction and the cermet structure characteristics. Methods of chemical kinetics, surface analysis and non-destruction control were used. A new method was worked out It allowed to estimate the specific crack size in the cermet matrix. Influence of the inclusion diameter and density as well as the matrix volume content on the peculiarities of cermet corrosion cracking was investigated using this method.