Glass–ceramic coatings on titanium alloys for high temperature oxidation protection: Oxidation kinetics and microstructure

• A glass–ceramic coating is applied on Ti6–Al–4V alloy.
• Oxidation resistance of titanium alloy is enhanced by the glass coating.
• Oxidation occurs at constant rate, of which the limiting step is oxygen diffusion.
• Microstructure evolution during oxidation is discussed.

A glass–ceramic coating is applied on Ti–6Al–4V alloy for oxidation protection at 800 °C. Its dynamic oxidation and microstructure evolution are investigated. The titanium alloy substrate is effectively protected by the glass–ceramic coating, of which the oxidation develops at constant rate. The linear relationship of oxidation is deduced dm/dt = Dρ(C1 − C2)/(bC′), and the diffusion coefficient of oxygen at 800 °C in glass is obtained. Oxygen diffusion through glass coating is the controlling step. After the initial firing, silicide interlayer forms between the glass coating and titanium alloy substrate, where the ratio of Ti/Si decreases after oxidation due to Si diffusion and Ti consumption.