Phase and element composition, microhardness of Ti-6Al-4V titanium alloy, Ti/Ti-6Al-4V and Zr/Ti-6Al-4V systems treated by compression plasma flows have been investigated in this work. X-ray diffraction, scanning electron microscopy, energy-dispersion X-ray microanalysis and Vickers microhardness measurements were used for samples characterization. The findings showed that treatment of the "coating/titanium alloy" system by compression plasma flows allowed decreasing the toxic elements (Al, V) concentration in the surface layer of Ti-6Al-4V titanium alloy. The variation of the energy absorbed by the surface layer resulted in the change of the element concentration and the formation of a number of phases in the modified layer: a solid solution on the basis of α' phase in Ti-6Al-4V and Ti/Ti-6Al-4V systems and β phase in Zr/Ti-6Al-4V system. The formation of δ-TiN x at the surface due to interaction of surface layer atoms with nitrogen atmosphere in the vacuum chamber was also found. The change of phase composition and quenching effects resulted in the microhardness increase.

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Erosion of the surface of St3 type steel and BrB2 type bronze samples as well as bronze and cop per samples with zirconium coating under the effect of compression plasma flows is studied. The results show the increase in mass removed from the surface of samples with the growth of energy absorbed by the surface layer and with the growth of the number of pulses. Probable mechanisms of erosion have been discussed. Ero sion leads to the decrease in the coating element concentration in the alloyed layer in the case of the coat ing/substrate system treatment. This effect depends on thermal characteristics of the treated material.

Cu-Ti alloys synthesized in the surface layer of copper by means of preliminary Ti coating deposition and subsequent treatment by compression plasma flows have been investigated in this work. X-ray diffraction, scanning electron microscopy, energy-dispersion X-ray microanalysis, Auger electron spectroscopy, Vickers microhardness measurements and tribological tests were used for Cu-Ti alloys characterization. The findings showed that the increase of the energy absorbed by the surface layer during plasma treatment from 57 to 74 J/cm 2 per pulse resulted in the growth of the alloyed surface layer thickness from 15 to 19 µm, more homogeneous distribution of Ti in the alloyed layer and the decrease of Ti average concentration from 13.1 to 9.7 at.% in it. The supersaturated solid solution of titanium in copper is the main phase constituent of the alloyed layer after treatment at 74 J/cm 2 . The synthesized surface of the Cu-Ti alloy possesses enhanced strength and tribological properties.

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