Wear Resistance of Ti-Mo-Si Coatings Formed by Electrospark Alloying on Titanium Alloy Ti-6Al-4V

Ti-Mo-Si coatings were prepared to protect of the titanium alloy Ti-6Al-4V from wear and high-temperature oxidation by the electrospark deposition method was investigated. To form the Ti-Mo-Si coating, a nonlocalized electrode consisting of titanium granules with the addition of silicon and molybdenum powders was used. The aim of the work is to study the influence of the silicon and molybdenum ratio in the non-localized electrode on the character of mass transfer during the electrospark deposition Ti-Mo-Si coatings, their composition, microstructure, oxidation resistance and tribological properties. To study the phase composition of the coatings, a Dron-7 X-ray diffractometer in CuKα radiation was used. According to the X-ray phase analysis data, the phases of αTi, Mo, Ti5Si3 and TiSi2 were found in the composition of the coatings. The average thickness of the prepared coatings was in the range from 31.70 to 40.97 μm. According to the energy-dispersive analysis data, titanium predominated in the composition of the coatings, the molybdenum concentration reached 18 at. %, and silicon — 9 at. %. It is shown that silicon particles participated disproportionately less in the coating formation compared to molybdenum particles. Oxidation resistance testing showed that the use of the developed Ti-Mo-Si coatings allows increasing the high temperature oxidation resistance of the titanium alloy Ti-6Al-4V at a temperature of 900 °C by up to 5.7 times. The microhardness of the Ti-Mo-Si coating surface was in the range from 5.81 to 9.88 GPa. It was found that with an increase in the silicon to molybdenum ratio in the non-localized electrode, the average values of the friction coefficient of the coatings in the dry sliding mode monotonically increased from 0.81 to 0.86. The use of Ti-Mo-Si coatings allows reducing the surface wear of titanium alloy products by up to 19 times. The highest hardness, wear resistance and oxidation resistance were demonstrated by the coating with the highest silicon content.

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