Optimization of the Composition, Structure, and Properties of Electrode Materials and Electrospark Coatings for Strengthening and Reconditioningof Metal Surfaces

摘要

The structure and phase composition of Ni-Cr-Al alloys doped with Si, Ti, Mn, and Co have been studied. An eutectic three-phase structure was found to be in the doped alloys. Doping with Si and Ti increases the microhardness and wear resistance of the alloys. The highest coefficient of the mass transfer (0.75) during the electrospark alloying is observed for Co-containig alloys. The coatings with the doped alloys have a higher wear resistance than those with the Ni-Cr-Al basic alloy. Steel 45's heat resistance is increased after the electrospark doping with Si-, Ti-, Mn-, and Co-containing alloys by 4, 4.3, 5.1, and 4.6 times, respectively. The electrode materials have been developed for the electrospark reconditioning of workpieces based on PE8418 (Ni-Ni_3B-Cu-Si) with the additions of titanium carbide, chromium carbide, and tungsten carbide, which make it possible to manufacture coatings up to 5-mm thick. The results of the investigation of the erosion properties of B_4C-TiB2 alloys manufactured using the method of reactive sintering under hot pressing of B_4C-TiO_2 powder blends that were used as the electrode materials for the electrospark hardening of titanium surfaces are presented. The tests show that, in the surface layers of the electrode materials, under the impact of the electric discharge, the boron carbide content substantially decreased, while the quantity of titanium borides increased and new phases of TiC_xN_y, TiO_2, and Ti appeared. Only these components are transferred onto the surface of the titanium alloy and form there a protective coating up to 100 μm thick with high hardness (32-43 GPa) and wear resistance. The materials developed are promising for their application as the electrodes in the electrospark alloying of construction steels and titanium alloys.