STUDY OF THE INFLUENCE OF THE ELECTROPULSE EXPOSURE ON THE FORMATION OF ELECTRIC ARC COMPOSITE CERMET COATINGS OF THE SYSTEM STEEL 65G – CR3C2
Abstract
Abstract. The most promising solution to the problem of strengthening and restoring the worn surfaces of machine parts and mechanisms is the deposition of protective thermal sprayed coatings, in particular with a cermet structure. The analysis of the scientific and technical literature shows that in recent times the most widely used cermet systems with carbides of chromium, titanium and tungsten, which are characterized by high cost due to the use of expensive sprayed materials and high-velocity methods for their deposition. In the work, for the first time, electric arc composite cermet coatings of the steel 65G-Cr3C2 system were obtained using the powder of the strengthening phase in free form due to the use of a modernized electric arc spraying gun EM-14M. The analysis of the microstructure of the obtained coatings showed that they are characterized by a porosity of about 11.5%, and the particles of Cr3C2 and steel 65G are well differentiated in the structure. Phases were identified by determining their chemical composition and it was established that the content of the carbide phase in the coating is 15.4% (vol.). In order to improve the physical and mechanical properties of the specified coatings, it is proposed to use electropulse exposure at optimal amplitude-frequency parameters (amplitude 5 kV, frequency – 6.5 kHz), which are characterized by ease of implementation and the use of inexpensive additional equipment. The comparative metallographic analysis of microstructures of the coatings showed that the electropulse exposure reduces the porosity of the cermet coating of the steel 65G-Cr3C2 system from 11.5% to 7.7%; there is an absence of areas of carbide particles pull-out and a decrease in the size of the structural components of the coating. It is shown that the use of electric pulse exposure provides an increase in the bond strength of coatings to the substrate made of steel 45 from 28 MPa to 34 MPa (+21.5%) and an increase in the microhardness of the metal matrix from 2.7 GPa to 3.25 GPa (+20%).
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