Lytvyn R. The Regularities of the Hard Wear Resistant Electrospark Coatings Formation Using Short High-Frequency Pulses

The purpose of work is to establish the regularities of electrospark coatings structure and properties formation after alloying materials on tungsten-carbide-based and titanium diboride electrodes by high-frequency microsecond electric pulses and mathematical modeling of mechanical and thermal interaction of the spark erosion products with a substrate for the purpose of coatings qualitative and functional characteristics increase. The object of the work is the wear proof electrospark coatings from alloys on WC and TiB2 basis. The mass transfer regularities during electrospark alloying of metal surfaces, as well as the electrospark coatings content, structure and properties versus electric discharge time and anode-cathode spacing size are studied. Optimal technological parameters ranges of alloying by electric pulses with 0,8-2,2 s duration providing high mass-transfer, qualitative and functional characteristics of coatings are established. Main principles are defined for choice of alloying regimes to reach the maximum compliance to structure of hardmetal WC-16% Co alloying electrode. On the grounds of the spark erosion products analysis it is ascertained that the mass transfer occurs in the form of fine liquid particles in consequence of the short spark pulses action with a localization of the latter and their lowered thermal-mechanical influence on electrodes surfaces. A new mathematic model is developed for mechanical and thermal interaction of the spark erosion products, in the framework of which it is computed their strain and heat exchange with substrate for the erosion anode products of different structure and size. Computed data are obtained of final particle strain degree as well as a probability of the particles adhesion on a substrate. Results of the work are realized in practice for surface hardening of ultrasound concentrators.