Wear Resistance of Ti–Mo–Si Coatings Formed by Electric Spark Alloying on Ti–6Al–4V Titanium Alloy

Abstract

Ti–Mo–Si coatings for protection of Ti–6Al–4V titanium alloy from wear and high-temperature oxidation applied by electrospark alloying are studied. To form the Ti–Mo–Si coating, a non-localized electrode consisting of titanium granules with the addition of silicon and molybdenum powders is used. A Dron-7 X-ray diffractometer in CuK_α radiation is used to study the phase composition of the coatings. According to the X-ray phase analysis data, the phases of αTi, Mo, Ti₅Si₃, and TiSi₂ are found in the coating composition. The average thickness of the prepared coatings is in the range from 31.70 to 40.97 μm. According to the energy dispersive analysis, titanium predominated in the coating composition, the concentration of molybdenum reached 18 at %, and silicon, 9 at %. It is shown that silicon particles participated disproportionately less in the formation of the coating compared to molybdenum particles. Heat resistance testing shows that the use of the developed Ti–Mo–Si coatings allows increasing the heat resistance of the Ti–6Al–4V titanium alloy at a temperature of 900°C by up to 5.7 times. The microhardness of the Ti–Mo–Si coating surface is in the range from 5.81 to 9.88 GPa. It is 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 increase 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 coating with the highest silicon content demonstrates the highest hardness, wear resistance, and heat resistance.