Effects of carbon addition on Ti–Al–Si coatings synthesized by self‐generated gradient hot‐dipping infiltration method

Abstract

AbstractThe effects of carbon addition on the microstructure and oxidation resistance of Ti–Al–Si coatings synthesized by the self‐generated gradient hot‐dipping infiltration method were studied. The microstructure, phase structure, as well as composition of the coating, were observed by using X‐ray diffraction, scanning electron microscope, and energy dispersive spectrometer. It was found that when carbon was added into the Al‐SiO2 system, the coating was composed of L‐(Al,Si) phase and Ti(Al,Si)3 phase. The thickness of the Ti(Al,Si)3 phase layer increased along with the dipping time. The cycle oxidation tests at 900°C for 160 h showed that the weight gains of the coating samples were only 8.1% of that of the Ti–6Al–4V alloy samples. This result indicates that the coatings remarkably enhanced the oxidation resistance of Ti–6Al–4V alloy, which could be ascribed to two reasons: (1) the mixed oxidation zone of Al2O3, Ti(Al,Si)3, and Ti5Si3 on top of the oxidized coating could act as a barrier to retard the diffusion of oxygen to the substrate; and (2) several new phase layers (Ti3Al, TiAl, and Ti5Si3 + TiAl2) near the substrate during oxidation could reduce the cracks at the bottom of the oxidized coating.