SURFACE MODIFICATION OF DIATOMITE-BASED MICRO-ARC COATINGS USING PULSED ELECTRON BEAM IRRADIATION

The influence of low‑energy high‑current electron beam (LEHCEB) treatment on the structure and properties of ceramic-like coatings based on diatomite with the addition of zirconium or titanium oxide particles was investigated. The bioresorbable Mg alloy MA2-1hp was used as the substrate material. For coating application, the micro-arc oxidation (MAO) method was used. Diatomite, an organogenic material based on silicon oxide (SiO₂) consisting of the shells of unicellular diatom algae, was used as the main substance for synthesizing the coatings. The surface of the synthesized coatings was subjected to pulsed electron beam irradiation with different energy densities: 2.5, 5 and 7.5 J/cm². The obtained coatings were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffractometry, scratch testing and potentiodynamic polarization. The internal structure and surface morphology, phase and elemental compositions, as well as adhesion strength and corrosion resistance of the treated coatings were studied. As a result of irradiation, the surface of the coatings underwent significant changes, forming a unique morphology characterized by smooth elevations and porous depressions. It was found that surface treatment of coatings with ZrO₂ particles contributed to the increase of their adhesion strength and corrosion resistance, since the critical load increased from 9.5 (for the original coating) to 18 N (for the coating subjected to LEHCEB-treatment with an energy density of 7.5 J/cm²), and the corrosion current density decreased from 7.53 ∙ 10^‒7 to 1.12 ∙ 10^‒8 A/cm². For coatings with TiO₂ particles, the opposite dependence was observed after LEHCEB treatment, the strength and corrosion properties deteriorated, which is related to the different thermophysical properties of zirconium and titanium oxides.

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