The Effect of Discharge Pulse Energy in Electrospark Deposition of Amorphous Coatings

摘要

This paper presents the results of studying an amorphous coating on a steel 35 substrate prepared by electrospark deposition in a mixture of iron granules with CBCrSiMoW powder. A prolonged duration of discharges increased the iron concentration in the composition of the coatings, decreasing a fraction of the amorphous phase from 67 to 50 vol %. The amorphous coating had a resistance to oxidation at a temperature of 700 degrees C that was 23 times higher than did steel 35. Polarization tests of samples in a 3.5% NaCl solution showed an increase in the corrosion current density with increasing pulse duration above 200 mu s. The microhardness of the coatings ranged from 399 to 759 HV. The average wear rate of the coatings under dry sliding conditions ranged from 1.6 x 10(-6) to 10.9 x 10(-6) mm(3)/Nm, which is from 4 to 22 times lower than that of uncoated steel 35. The coating obtained with the longest pulses exhibited the highest friction coefficient and wear rate due to the lowest concentration of the amorphous phase. The results suggested that, to ensure sufficient coating thickness and an acceptable concentration of the amorphous phase, the optimal duration of the discharge pulses should range from 50 to 200 mu s.