Vronska Y. Thermokinetics and staged cellular precipitation in bulk material and electrospark coating of alloys of the Co-W system

The dissertation is devoted to research of features of a course of cellular precipitation in various systems. The method for determining the stages of the Pb-Sn system was tested. The study was performed by the method of differential hydrostatic weighing. The data on the phasing of the system were compared by hydrostatic weighing with resistometry data. A satisfactory correlation was obtained. This allows us to conclude that it is appropriate to use the proposed method to determine the phasing of systems that age by the cell mechanism. The staging of the Co-W system in the temperature range 873 - 1173 K was determined using dilatometric isotherms. It is established that at the lowest research temperature the decomposition of supersaturated solid solution occurs in three stages. This is due to the fact that the supersaturation of the solid solution is sufficient to initiate not only the secondary but also the tertiary reaction. At the same time, at temperatures close to the upper limit of the cellular reaction, the decay occurs in only one stage. The external influence on the initiation of cell decay is analyzed on the example of steel. It is shown that the electrospark alloying of 30HGSA steel with chromium leads to the formation of a layered multiphase system on its surface, consisting of its own coating and transition zone. Vibration loads increase the thermodynamic stability of the system, resulting in a redistribution of the main lung elements of the system and the replacement of metastable phases with stable ones. It was established for the first time that in the electrospark coatings with chromium on 30HGSA steel under the external influence (alternating deformation, temperature) the decay of BCC-solid solution based on -iron by the mechanism of cellular precipitation.