Influence of corrosion-active non-metallic inclusions on the accelerated destruction of the internal surface of the Oplot-M tank barrel

Abstract

The metallographic features of operational damage to the inner surface of the barrel of the Oplot-M tank were analyzed. It was established that with the movement from the chamber to the cut of the barrel, the number and size of damage decreases, which is related to the distribution of pressures of working gases, temperature and aggressiveness of the environment. It is shown that the damage is placed on the inner surface chaotically and the nature of their destruction is corrosive and corrosive-mechanical in origin. Local analysis of their chemical composition revealed a high oxygen content, which indicates the formation of oxide-hydroxide compounds. The surface layers of the barrel were studied and it was established that a "white" layer with a thickness of ~50 μm and a microhardness of 930 kg/mm2 is formed on the surface, the structure of the inner layer of the steel of the barrel is troostite (HW 225 kg/mm2). 
 The effect of corrosion-active non-metallic inclusions (KANV) on the destruction of the surface of a barrel made of steel 38KHN3MFA was studied. It is shown that more sensitive to changes in the technical state of steel due to degradation are studies of corrosion resistance, microelectrochemical heterogeneity and impact toughness of steel. It was established that the presence of KANV in the steel structure leads to an increase in corrosion currents by 4 times and microelectrochemical heterogeneity, in particular, non-periodic potential peaks of 50-70 and 200-230 mV. Due to the influence of tap water on the surface of the steel, corrosion ulcers of a rounded shape and a size of 50-80 μm were recorded, which contribute to the local corrosion of the steel. The analysis of steel fractures revealed that inclusions of a round shape with a size of 3-5 μm contain impurities of harmful elements Al, Mg, F, which accelerate local corrosion on the surface of the steel of the tank barrel. It is shown that the study of fractures, and not of samples, provides an opportunity to estimate not only the size and density of inclusions, but also their chemical composition.