Reactive plasma spraying of titanium in nitrogen containing plasma gas

The low hardness and the poor tribologic characteristics of titanium can be positively modified by means of reactive plasma spraying. The present study describes experimental results concerning reactive low pressure plasma spraying of pure titanium powders in an Ar/N2 plasma gas in order to obtain thick titanium composite coatings with a high percentage of hard titanium nitrides (TiN and Ti2N). As measured by means of X-ray diffraction, the volume fraction of nitrides in the coating with increases increasing nitrogen content in the plasma gas mixture and with increased spraying distance. The nitrogen content of the coating shows a linear relationship with the microhardness of the coating. By varying the Ar/N2 plasma gas ratio, adherent hard composite coatings, up to Knoop 1200 hardness and with low porosity are obtained. Such characteristics make them particularly suitable in all those technological applications where good corrosion resistance of titanium and high tribologic properties are required.