Structure and Properties of High-Speed Steel Surfaised Layer Irradiated by Pulsed Electron Beam

Abstract

The methods of light, scanning, and transmission electron microscopy are used to study the structure, phase composition, and properties of multilayer plasma surfacings made of high-speed steel R18YU in a protective-alloying nitrogen medium, followed by a fourfold high-temperature tempering and additional electron beam processing. After tempering, the deposited layer on the 30KHGSA high-speed steel R18YU has a polycrystalline structure with a cell size of 7–22.5 µm with layers of the second phase along the boundaries and at the joints of the grains. It is shown that the irradiation of surfaised layers with a pulsed electron beam (energy density 30 J/cm², pulse duration 50 µs, number of pulses 5, and pulse repetition rate 0.3 s^–1) leads to the formation of a thin (30–50 µm) surface layer with a cellular crystallization structure. The volume of grains is formed by a solid solution based on α-Fe. Nanoscale (10–45 nm) particles of iron, chromium, and tungsten carbides of complex composition, such as M₆C and M₂₃C₆, are located in the volume and along the boundaries of the crystallization cells. Fragmentation of the surface layer by a grid of microcracks is revealed, indicating relaxation of thermal stresses formed during high-speed cooling after electron beam processing. The particles have a faceted or globular shape. After irradiation with an electron beam, the wear resistance of the material increases by more than 3 times, while maintaining the microhardness of the modified layer (~5.3 GPa).