On the management of nanostructuring of electric spark coatings

Abstract

Analysis of the literature data indicates the great attention of specialists to the formation of ultrafine-grained (UFG) and nanocrystalline (NC) structures. Such structures are obtained by severe plastic deformation and other methods to improve the bulk properties of materials. Improving the properties of the surface layers of materials is achieved by modifying them with the formation of NC structures by different methods. In the article, in the development of earlier work, the results of studies of the formation of such structures by the method of electrospark alloying (ESD) are reflected. The aim of this work was to obtain experimentally quantitative data on the nanostructuring of electric-spark (ES) coatings, specifying the effect of the technological parameters of ESD and electrode material on this process. The studies included the determination of the energy parameters of the ESD process, changes in the mass of samples to obtain pulsed values, as well as the grain size of the structure of ES coatings. At the same time, modern certified technological and research equipment and recognized methods were used. The studies were carried out in a wide technological range: pulse energy E = 0.045…0.29 J, their duration t imp = 20…80 μs, frequency f imp = 300…1500 Hz, the conditional value of the specific processing time t sp = τ…5τ. The result of the work is the following: coatings are obtained with a content of 5 to 50 % of the granular structure of the nanoscale level using electrodes made of hard alloys VK8 (92WC + 8Co) and STIM-3BOA n (72TiC +17.5Cr 3 C 2 +10Ni + 0.5Al 2 O 3 nano); it was found that an increase in the pulse energy leads to an increase in the grain size of the nanoscale level and a decrease in their fraction in the coating, and an increase in the pulse frequency and specific ESD time, on the contrary, to a decrease in the grain size and an increase in their number; the use of anode materials with a refractory nanocomponent also contributes to the nanostructuring of ES coatings. In developing this topic, attention is drawn to one of the important issues requiring separate studies-this is the study of the role and efficiency of pulses of the low-energy zone of electric regimes in the process of nanostructure of ES coatings.