Structure, Phase Composition, and Surface Properties of R2M9 High-Speed Steel

Abstract

Plasma surfacing with a thickness of 4–5 mm (argon-plasma-forming gas) was carried out in a protective alloying atmosphere of nitrogen using a non-current-carrying filler flux-cored wire PP-R2M9. Using methods of modern physical materials science, the structural-phase states, microhardness, and tribological properties of surfacing high-speed steel R2M9 on medium-carbon steel 30KhGSA were studied. It has been established that the deposited layer is characterized by the presence of a carbide frame. The main phases of the deposited layer are a solid solution based on α-iron (63 wt %) and carbides of complex composition Me₆C, Me₂₃C₆, and Me₇C₃ (34 wt %). The γ-iron based solid solution is present in a small amount (3 wt %). Carbides of the Me₆C type, which are the main carbide phase, are localized at the boundaries and in the bulk of α-phase grains, while molybdenum carbide particles of the Mo₂C composition are found only in the bulk of the grains. At the junctions of α-phase grains, plastic eutectic grains enriched in atoms of iron, molybdenum, tungsten, and carbon are observed. The microhardness of the deposited layer varies across the cross section from 6.6 to 5.2 GPa, the wear parameter is 1.5 × 10^–5 mm³/(N m), the friction coefficient is 0.57, and the scalar density of randomly distributed dislocations is 7.6 × 10¹⁰ cm^–2.