Storozhenko M. Physical-technological fundamentals of the creation of "Ni(Fe)-based alloy - MeB2" composite materials for coatings with high wear-resistance

The thesis deals with the solution of important scientific and technical problem of increasing the coatings wear resistance by the development and testing of new approaches to the creation of "Ni(Fe)-based alloy MeB2" composite materials with controlled structural-phase composition. The method of liquid-phase sintering in a vacuum environment, followed by grinding and classification, is proposed for obtaining the composite powder materials of TiB2−(Fe−Mo) and NiFeCrBSiC − MeB2 systems. The processes of interfacial interaction between the alloy and the refractory compound during sintering define the coatings structure and properties. Therefore, the composite materials composition was determined by studying the wetting behaviour and interfacial interaction between the refractory compounds and the metal alloys. The chemical interaction during the TiB2−(Fe−13wt.%Mo) composite materials sintering leads to the in-situ formation of Mo2FeB2 borides. Due to the high hardness (22–24 GPa) the Mo2FeB2 borides effectively increase the wear resistance of gas-thermal and electro-spark coatings under the conditions of abrasive wear and sliding friction. Due to the optimum ratio of boride reinforcements (TiB2 and Mo2FeB2 particles) and metal matrix, the developed TiB2–40wt.%(Fe−13wt.% Mo) plasma and detonation coatings are characterized by higher wear resistance than that of the WC-6%Co coatings. According to the results of wetting behaviour investigation, the TiB2 and CrB2 additives were selected to reinforce the NiCrBSiC (ПГ-СР3) and FeNiCrBSiC (ПГ-Ж14) self-fluxing alloys. The chemical interaction in NiFeCrBSiC − MeB2 systems results in the in-situ formation of chromium borides and carbides, which due to high level of hardness (20-24 GPa) reinforce additionally the coatings structure. The technological solutions, proposed in the term of thesis, make it possible to control the structural-phase composition of composite materials and thermal-sprayed coatings of NiFeCrBSiC-MeB2 systems, namely the amount and size of in-situ formed chromium boride and carboboride phases. Under the conditions of sliding friction at high temperatures (200−400 °C), the developed thermal-sprayed coatings NiFeCrBSiC−MeB2 have wear resistance by 2-3 times higher than that of commercial coatings FeNiCrBSiC (ПГ-СР3, ПГ-Ж14) and NiCrBSiC-35%wt.WC (ПС-12НВК-01). The developed thermal-sprayed and electrospark coatings were tested at industrial enterprises of Ukraine.