Improvement of adhesive strength of Ti–Al plasma sprayed coating

In order to improve the adhesive strength of plasma sprayed titanium coating, titanium–aluminum mixed powder was used as a material for plasma spraying. Adhesive strength of the plasma sprayed Ti–Al coatings was examined by changing the Al powder ratio in the Ti–Al mixed powder and input electrical power to the plasma torch. And then, they were discussed from the points of microstructure, hardness and oxygen and nitrogen contents of the coating. The plasma sprayed Ti–Al coating was found to be composed of Al and Ti compounds of TiN0.3, Ti(N,O) and Ti3Al, which were synthesized during the powder particles flight in plasma jet. The adhesive strength of the coating was improved by filling cracks and pores of the Ti compounds layers with the Al phase to form a dense microstructure, and also by hardening the Ti compounds and Al phase with the oxygen and nitrogen contained in the coating.