Vladislav Kolnyshenko’s research while affiliated with Peter the Great St.Petersburg Polytechnic University and other places

Super 13Cr steels, which combine high strength and excellent corrosion resistance, are the optimal choice for developing and exploiting complex oil and gas wells, particularly in high-CO2 environments. In this study, we conducted a corrosion assessment of several high-strength steels of the 13Cr type with different alloying systems. We identified the primary parameters responsible for the corrosion resistance of these steels based on our research findings and suggested ways to optimize their chemical composition and select the most economically viable option. We demonstrate the importance of selecting the appropriate alloying system and the impact of non-metallic inclusions (NMIs) on the corrosion properties of the high strength 13Cr material.

Non-metallic inclusions (NMIs) in steel have a negative impact on the properties of steel, so the problem of producing clean steels is actual. The existing metallographic methods for evaluating and analyzing nonmetallic inclusions make it possible to determine the composition and type of NMIs, but do not determine their real composition. The analysis of single NMIs using scanning electron microscope (SEM), fractional gas analysis (FGA), or electrolytic extraction (EE) of NMIs is too complicated. Therefore, in this work, a technique based on the automatic feature analysis (AFA) of a large number of particles by SEM was used. This method allows to obtain statistically reliable information about the amount, composition, and size of NMIs. To analyze the obtained databases of compositions and sizes of NMIs, clustering was carried out by the hierarchical method by constructing tree diagrams, as well as by the k-means method. This made it possible to identify the groups of NMIs of similar chemical composition (clusters) in the steel and to compare them with specific stages of the steelmaking process. Using this method, samples of steels produced at different steel plants and using different technologies were studied. The analysis of the features of melting of each steel is carried out and the features of the formation of NMIs in each considered case are revealed. It is shown that in all the studied samples of different steels, produced at different steel plants, similar clusters of NMIs were found. Due to this, the proposed method can become the basis for creating a modern universal classification of NMIs, which adequately describes the current state of steelmaking.