Low-energy high-current electron beam treatment of composite coatings based on diatomite and ZrO2 particles

The influence of low-energy high-current electron beams (LEHCEB) on morphology, structure and functional properties of micro-arc coatings based on diatomite and ZrO2 particles was studied. The coatings were treated at energy densities of 0, 2.5, 5.0, and 7.5 J / cm2. Advanced techniques such as scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, scratch testing, immersion testing in 0.9 % NaCl solution, as well as potentiodynamic polarization were used to investigate the coatings. It was established that after the LEHCEB treatment at energy densities ranging from 2.5 to 7.5 J / cm2 there was partial or complete melting of ZrO2 particles and their dissolution in the coating. At the same time, the phase composition of the coating changed insignificantly. A distinctive surface relief consisting of depressions and elevations was formed on the surface of the coatings, which is especially characteristic of the coatings treated at an energy density of 7.5 J / cm2. The corrosion resistance of the coatings increased significantly, as evidenced by the decrease in corrosion current from 7.48×10-7 to 1.05 ×10-8 A / cm2 and the increase in polarization resistance from 0.9 ×104 to 5.77 ×106 Ω·cm2. In addition, the adhesion strength of the coatings has also increased, as evidenced by the increase in critical load from 9.9 to 19.2 N. This is due to the fact that the LEHCEB treatment resulted in a denser coating and the pores became spheroidal in shape. In addition, a surface dense molten coating layer enriched with zirconium was formed.