Влияние добавки Al2O3 в анодный материал WC – 8 Co на формирование покрытий, полученных электроискровым легированием

Abstract

WC – Co coatings are widely used due to their high hardness and wear resistance, however, they have low resistance to high-temperature oxidation and therefore need modification with heat-resistant compounds. Anode materials based on WC – 8 % Co with the addition of 1, 3 and 6 wt. % Al2O3 for applying electric spark coatings on steel 35 were prepared. During the deposition of coatings, the erosion of the anode, of the total cathode weight gain the and the mass transfer coefficient were investigated. X-ray phase analysis of coatings showed the predominance of tungsten subcarbide in their composition. According to scanning electron microscopy and energy dispersion analysis, aluminum oxide was found in the structure of coatings in the form of micron and fine inclusions. Moreover, its amount in the coatings increased with an increase in the content of Al2O3 in the anodes. Potentiodynamic tests of the samples showed an increase in the corrosion potential and a decrease in the corrosion current density with an increase in the Al2O3 content in the coatings. The heat resistance of coatings at a temperature of 700 °C increased monotonically with an increase in the concentration of aluminum oxide. For 100 hours of testing, the weight gain of the samples with coatings was from 4 to 11 times less than that of uncoated steel 35. The microhardness of the alloyed layers ranged from 13 to 15.6 GPa, which is 4.6 to 5.4 times higher than steel 35. The coating with the highest concentration of aluminum oxide had the highest hardness. The wear rate of the coatings was 3.9 to 12.5 times lower compared to steel 35. With an increase in the concentration of Al2O3 in the anode material, the wear of electric spark coatings monotonically decreased from 1.45·10–5 to 0,45·10–5 mm3·N–1·m–1.