Wear-Resistant Cr–Fe–Al2O3 Coating Deposition on Steel 35 Using Aluminum Oxide Powder

Using electrospark alloying, Cr–Fe–Al₂O₃ coatings are obtained on steel 35 in a mixture of steel granules with chromium and aluminum oxide powders. The structure of the coatings is studied using X-ray diffraction analysis, scanning electron microscopy, and X-ray spectral microanalysis. The heat resistance of the coatings was studied for 100 h at a temperature of 700°C in air. The study of the mechanical properties of the coatings includes testing for microhardness under a load of 0.5 N and wear in the dry friction mode under a load of 25 N. According to X-ray diffraction analysis, the coating composition is dominated by ferrochrome and a small amount of aluminum oxide. According to EDS analysis, the element distribution in the coating is uniform throughout the coating thickness with a chromium concentration of about 60 at %, iron, 30 at %, and aluminum, 3.4 at %. The results indicate a uniform distribution of fine particles of aluminum oxide in the volume of the deposited layer. It has been shown that the metal powder participates four times more actively in the formation of the coating compared to the granules. The heat resistance test shows that with addition of Cr–Fe–Al₂O₃ powder in the anode mixture, the average rate of high-temperature weight gain of the samples increases. In general, the use of Cr–Fe–Al₂O₃ coatings increases the heat resistance of steel 35 from 2.4 to 4 times. The average values of the friction coefficient of coatings range from 0.76 to 0.83, with a minimum for the sample deposited using a minimal addition of Al₂O₃. The wear of the samples decreases monotonically from 3.3 × 10^–6 to 1.8 × 10^–6 mm³/(N m) with a decrease in the concentration of aluminum oxide in the anode mixture. In general, the application of Cr–Fe–Al₂O₃ coatings using the proposed method makes it possible to increase the wear resistance of the steel 35 surface from 11 to 20 times.