High-Speed Steel Technology Substitution in Mining Machinery – an Experimental Study

Abstract

The growth of mineral extraction in countries with a developed mineral resource sector under conditions of external restrictions requires the modernization of the domestic mining machinery – an indispensable condition of which is the replacement of technologies for the production of high-speed steels and machine tools. This research was aimed at experimental studies of microstructure, phase composition and microhardness distribution in the surface layer of the R6M5 high-speed steel samples after laser cutting, cold treatment and laser tempering. It was demonstrated that after laser cutting in the surface layer of the cut there was the carbide dissolution and enrichment of the metal matrix with carbon and alloying components, resulting in an increase of residual austenite content up to 50...60 %. After the cold treatment in liquid nitrogen the content of residual austenite decreased up to 7...9 %. The laser cut surface microhardness increased up to 1000...1100 MPa. At further laser tempering the dispersion hardening processes took place, as a result the V2C carbides appeared in the steel structure amounting to 4.7 %. The microhardness increased up to 10400...10600 MPa. The study showed the possibility of using the high-speed steel laser cutting not only as a separating operation, but also as a hardening treatment. The findings contribute to the technological support for the development of domestic mining machinery in terms of replacing imported high-speed steels and machine tools.