Rezumat
CZU 621.9.048.669.268
DOI https://doi.org/10.5281/zenodo.1053729
Consistencies were studied and quantity data collected about an effect of processing time and discharge energy on the thickness, micro-hardness and roughness of consolidated layers during electric-spark alloying of the steel surfaces with graphite. It was found that the thickness of the strengthened layer increases with the gain of the discharge energy and the time of alloying. In the study, the following materials were used: specimens of steels 40Х, З8ХМЮА, 40ХН2МЮА, 30Х13, АРМКО-iron, 12Х18Н10Т as well as steel 20, graphite ЭГ-4. Tests were carried out on devices: «EILV-8А», «EILV-9», «Elitron-22А» и «Elitron-52А», that provide the discharge energy in the range 0.1–6.8 J. The experiments demonstrated that the depth and the micro-hardness of the consolidated layer treated with the same technological regime are significantly different for different steel grades. The depth of consolidation increases with a higher initial carbon content in the steel. The higher the discharge energy, the greater this difference. Wear tests showed that usage of the method of nonabrasive ultrasound final processing after electric-spark alloying with graphite is effective and allows increasing wear-resistance of specimens by 7.8 times for steel 40X and by 11.5 times for steel 12Х18Н10Т. The research confirmed that the staged electric-spark alloying of specimen surface after consolidation with graphite electrode is effective for roughness decreasing. The discharge energy was lowering at each next stage. The staged electric-spark alloying of the consolidated layer of steel 38ХМЮА with graphite allowed decreasing of the surface roughness from Rа = 11.9–14.0 µm to 0.8–0.9 µm. The industrial tests showed that the electric-spark alloying with graphite offers solutions to a number of practical tasks.
Keywords: graphite, electric-spark coating, spark discharge energy, consolidation layer, wear-resistance, surface roughness, micro-hardness, alloyed steel.