Formation Features of Electrospark Coatings on Chromium Substrate Using ZrSi2–MoSi2–ZrB2 and HfSi2–MoSi2–HfB2 Ceramic Electrodes

Abstract

The work is devoted to the study of the features of mass transfer, structure, and properties of electrospark coatings on substrates made of the chromium alloy grade VKh1-17A using SHS-electrode ceramics of the compositions ZrSi₂–MoSi₂–ZrB₂ and HfSi₂–MoSi₂–HfB₂. The coatings were studied using X-ray diffraction, scanning electron microscopy, energy-dispersive analysis, and tribological tests using the “pin-on-disk” test; nanoindentation was also carried out. The kinetics of the mass transfer and heat resistance of coatings were determined by the gravimetric method. In accordance with the Palatnik criterion, the formation of coatings occurred in the form of an alloy of anode (electrode) and cathode (substrate) materials, which ensures high adhesion of the surface layer. The maximum weight gain on the cathode was observed after the first minute of treatment, and a decrease in the mass of the cathode was subsequently noted. As a result of electrospark deposition, coatings with 100% continuity and a thickness of 10–20 µm were deposited on the surface of the chrome alloy VKh1-17A. Zirconium-containing coatings are characterized by a hardness of 18.2 GPa and an elastic modulus of 274 GPa, and coatings obtained using the HfSi₂–MoSi₂–HfB₂ electrode were characterized by a hardness of 16.9 GPa and an elastic modulus of 332 GPa. The use of SHS-electrodes made it possible to increase the hardness of the surface layer of the chromium alloy by four times, wear resistance by 1.5 times, and oxidation resistance by 1.6 times at 1000°C for 30 h of testing.