Influence of plasma spraying parameters on the carbon content and porosity of TaC coatings

The optimization of a plasma-sprayed TaC coating process under controlled atmospheric and temperature conditions is described. The use of an inert argon atmosphere allows coatings to be obtained from materials with high melting points that are sensitive to oxidation. Correlations were established between the nature of the plasma gas, the temperature and velocity of the particles in the plasma jet and the chemical properties of the final coating. Increasing the are current increases the particle velocity and decreases the coating porosity. The advantages of adding helium to the plasma gas mixture were confirmed. Increasing the He concentration in an Ar-H, plasma improves the melting of the TaC particles, but also lowers the C/Ta atomic ratio and results in the formation of small quantities of Ta2C.