Application of a Novel Process Called Vacuum-Encapsulated Slurry Method to Form a Silicide-Aluminide Protective Coating on Ti6Al4V Alloy

In the present work, a novel process called vacuum-encapsulated slurry method is used to form the silicon-modified aluminide coating on Ti-6Al-4V alloy. In this research, the microstructure and high temperature oxidation resistance of such a coating have been investigated. The obtained coating had a triple layer structure. The inner layer was TiAl 2 , the middle layer contained very thin Ti 5 Si 3 lamellae within the TiAl 3 matrix, and was ultimately the outermost layer of Ti(Al,Si) 3 into which the Ti 7 Al 5 Si 12 particles were distributed. The evaluation of isothermal oxidation at 700 °C for 400 h revealed that the formation of silicon-modified aluminide coating is able to improve the high temperature oxidation resistance of the uncoated Ti-6Al-4V alloy. It should be noted that the remarkable improvement in the high temperature oxidation resistance of the sample coated with the silicon-modified aluminide coating produced by the vacuum-encapsulated slurry method is due to the fact that the protective Al 2 O 3 + SiO 2 mixed oxide scale along with the continuous, compact and uniform layers of Ti(Al,Si) 3 and Ti 5 Si 3 act as a barrier against oxygen diffusion toward the Ti-6Al-4V substrate surface during the high temperature oxidation.