INVESTIGATION OF TANTALUM AFTER EXPLOITATION IN CHLORINE-CONTAINING ENVIRONMENTS

The results of the study of the composition, structure and mechanical properties of tantalum after operation for 6 years in a chlorine-containing environment of the chemical industry are presented. It is concluded that tantalum has sufficient corrosion resistance, static and cyclic strength, high ductility and toughness. The results of the metal examination of the injection device (nozzle) showed that the damage to the tantalum pipes was caused by overheating of the metal. Using energy dispersion analysis (EDA), the change in the chemical composition of tantalum along the wall thickness of the pipe after operation was investigated. It was found that during overheating, an increase in the oxygen content in the metal under study to 5…8 % (atomic) / 0,56…0,82 % (weight) resulted in an increase in hardness by 4.4 times, microhardness by 4.7 times, and a decrease in impact performance by 9.8 times. As a result of serial tests, a non-monotonic dependence of the impact operation on the overheating temperature was obtained, due to the course of two mutually opposite processes ‒ an increase in viscosity due to the thermal activation of deformation processes and a decrease in viscosity as a result of the interaction of tantalum with oxygen. The mechanisms of tantalum destruction have been studied by modeling thermal and mechanical effects using electronic fractography. By comparing the ratio of fracture elements obtained during operation and during modeling of temperature and force effects in laboratory conditions, it was found that the destruction of tantalum occurred from shock load after overheating to a temperature close to 1000 °C. The experimental material obtained by modeling the effect of operation parameters on tantalum pipes can be used in the diagnosis of elements of technical devices made of tantalum, as well as determining the causes of their damage.