SELECTION OF THE NANOSCALE PHASE MATERIAL AND ESTABLISHMENT OF MODES FOR APPLYING NANOCOMPOSITION ELECTROPLATING COATINGS BASED ON CHROMIUM

The article presents the results of research on the establishment of an effective nanoscale phase and modes of applying nanocomposite electroplating coatings based on chromium. As a result of the conducted studies, it was found that it is advisable to use a nanodispersed aluminum oxide powder as a nanoscale phase. The method of mathematical planning of the experiment was used to determine the optimal modes of coating and the concentration of nanoscale particles in the electrolyte. The microhardness of the obtained coatings was chosen as an optimization parameter, since it significantly affects their wear resistance. The highest microhardness of a nanocomposite electrolytic coating based on chromium is achieved when the electrolyte is heated to a temperature of 50 °C, a current density of 59 A/dm2 and a concentration of nanoscale phase particles in the electrolyte of 3.2 g/l, which ultimately corresponds to an increase in microhardness to 14.32 GPa. It is also established that nanocomposition coatings have a positive microhardness gradient in thickness, which allows leveling the difference in the values of the microhardness of the coatings and the base metal and will help to increase the adhesion strength of the coatings to the base on the one hand and their wear resistance on the other. Based on the microhardness measurements of chromium-based nanocomposition coatings, statistical series were formed. 30 samples were subjected to measurements. According to the results of microhardness measurements, the average square deviation of the values of nanocomposition coatings based on chromium was 0.05 (coefficient of variation 0.283). To equalize the obtained experimental microhardness information, the law of normal distribution is chosen, since the coefficient of variation, according to which the greatest probability of microhardness values of nanocomposite coatings based on chromium is observed in the range of 14.32–14.37 GPa.