The paper concerns improving the microhardness and wear resistance of steel 45 by the combined treatment of electroexplosive borocoppering with the subsequent electron-beam treatment. It is found that surface roughness at the area of the electroexplosive treatment increases along with the absorbed power density and the mass of boron powder. The electron-beam treatment leads to a decrease of roughness and appearance of craters instead of radial melt flow traces. The depth structure of the electroexplosive alloying area with a thickness of 25 µm includes a coating layer, near-surface, intermediate, and boundary layers. The surface microhardness and the depth of the hardening zone after the electroexlosive alloying increase along with the absorbed power density and boron concentration and reach the values of 1400 HV The electron-beam treatment causes merging of the coating and the surface layers and increases the hardening zone depth up to 80 µm. A cellular or dendritic crystallization structure is formed near the surface, and a grain structure is formed in the depth. The inhomogeneous distribution of alloying elements over the volume of the alloying area and its adjustment during the electron-beam treatment are established. The inter-dendritic distances and grain diameters increase as the absorbed power density becomes higher with the increase of the electron-beam treatment exposure time. Also, the size of martensite needles increases in the depth. The combined treatment produces the sub microcrystalline strengthening phases-borides FeB, Fe2B, FeB2, carboboride Fe23 (C, B)6 , and carbide B4C. The microhardness level is reduced to 800 HV, and the wear resistance increases up to five times when compared to the wear resistance of the base.
Increase in wear resistance of nickel plasma coatings under traditional and combined treatment conditions
