Detonation spraying of titanium and formation of coatings with spraying atmosphere-dependent phase composition

•Composite coatings can be produced by reactive detonation spraying of titanium.•The coating composition depends on the composition of the spraying atmosphere.•Nitridation of titanium is enhanced when N2 is added into the O2 + C2H2 mixture.•At O2/C2H2 = 0.7 and N2 used as a powder carrier gas, titanium carbonitride forms.•Coatings are composed of alternating layers differing in elemental composition.

The phase development in the coatings formed by detonation spraying of titanium in a wide range of compositions of the spraying atmosphere is reported. The phase composition of the coatings was found to be very sensitive to the O2/C2H2 ratio and the nature of the powder carrier gas. Using O2/C2H2 = 1.1 and air as a carrier gas, titanium oxynitride-containing coatings were obtained, while at O2/C2H2 = 2.5, titanium oxides were the reaction products. In highly reducing conditions at O2/C2H2 = 0.7 and with the use of nitrogen as a carrier gas, titanium carbide and carbonitride formed. Higher contents of nitrides in the coatings were found when nitrogen was added into the O2 + C2H2 mixture. Metal-ceramic coatings formed at high transformation degrees of titanium were either composed of metallic titanium-rich particulate agglomerates distributed in a ceramic-rich matrix or contained alternating layers rich in metallic titanium and rich in ceramic compounds.