Home > Nanoparticles Improve Abrasion and Corrosion Resistance of Magnesium Alloys

Nanoparticles Improve Abrasion and Corrosion Resistance of Magnesium Alloys

Edit: Ccdanni 2020-03-17 Mobile

  Magnesium alloy has small density, high strength, large elastic modulus, and strong ability to withstand impact loads. It has been used in aerospace, aerospace, transportation, chemical, rocket and other industrial fields. However, magnesium alloys have poor abrasion resistance and corrosion resistance, and often need to be strengthened by surface treatment. Plasma electrolytic oxidation (PEO) is one of the main methods for preparing protective coatings for magnesium alloys. With the development of the industry, the performance of existing coatings has limited the further application of magnesium alloys.

  A new study jointly conducted by the Russian Academy of Sciences and the Russian Far Eastern Federal University shows that the incorporation of TiN nanoparticles into PEO coatings can significantly improve the mechanical properties of magnesium alloy surfaces. The wear resistance of the PEO coating containing TiN nanoparticles is 2.2 times that of the base PEO coating. The research will expand the application of magnesium alloys in the aerospace, automotive, high-tech product and equipment development industries. A related paper entitled "Hard wearproof PEO-coatings formed on Mg alloy using TiN nanoparticles" was published on Applied Surface Science on February 15.

  Paper link:

  https://doi.org/10.1016/j.apsusc.2019.144062

  Plasma electrolytic oxidation (PEO) can obtain anti-corrosion, wear-resistant protective PEO coating with high adhesion on metals and alloys without thorough surface treatment. The authors applied this method and added TiN nanoparticles to the electrolyte. Finally, a PEO coating containing nanoparticles was prepared on the MA8 magnesium alloy plate. The effects of different nanoparticle concentrations on coating properties were discussed.

  The study found that the high conductivity of TiN nanoparticles caused the anode voltage to decrease during the initial process stage and the cathode current to increase. During the preparation, part of the TiN particles will undergo a chemical reaction, and the upper layer of the coating will be oxidized and TiOxNy and TiO2 will be generated. The element distribution in the coating depends on the two phases where the particles are bound to the coating. The first phase is the absorption of TiN due to the electrophoresis of the anode; the second phase is the chemical reaction triggered by the plasma spark and arc discharge, so the oxidation generated Substances mainly exist in the upper layer of the coating.

  Fig.1 XPS spectrum of PEO coating formed in electrolyte containing 3 g / l TiN nanoparticles

  Figure 2 Schematic diagram of the formation process of PEO coating

  The comparison found that different TiN content will cause the morphology of the coating surface to be different. The increase in nanoparticle concentration leads to a decrease in the average pore diameter of the coating. When the TiN concentration is above 2 g / l, the surface roughness of the coating increases significantly, which is caused by the nanoparticles entering the pores of the coating. According to the performance test of the coating, it can be found that the Vickers hardness value of the coating containing nanoparticles is as high as 4.5 Gpa, which is much higher than the hardness of the coating without nanoparticles (2.1 ± 0.3 GPa). When the nanoparticle concentration is 3 g / l, the wear resistance of the coating is the highest, and the wear resistance decreases at 4 g / l. The coating also has high corrosion resistance, and the measured value of the impedance modulus at the lowest frequency is two orders of magnitude higher than that of the MA8 magnesium alloy without the coating.

  Figure 3 3D surface morphology of the coatings obtained in different electrolytes

  A number of studies have shown that the formation of PEO coatings in electrolytes containing other nanoparticles can occur similarly to this study, but the differences in the basic electrolyte composition and particle characteristics (size, melting point, and chemical stability), and the incorporation of nanoparticles The mechanism of the coating may be completely different.

  In summary, TiN nanoparticles have been successfully incorporated into the PEO layer formed on the MA8 magnesium alloy. The hardness and abrasion resistance of the coating containing the nanoparticles are twice that of the non-nanoparticle coating and have a higher resistance. Corrosion performance. This study provides guidance for future research on nano-particle-containing PEO coatings, expanding the application field of magnesium alloys, especially in industries that need to prevent mechanical damage and corrosion resistance.

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