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.