Temperature dependence of Ti6Al4Al Etching with Chlorine Gases as function of surface powder oxidation

We investigated the reactive etching for Ti6Al4V metal powder with an oxidizing gas as a function of the surface powder oxidation. XPS spectra of Ti6Al4V samples show the depth and composition of the complex oxide layer increases with wt% of oxygen. The reaction was performed in a fluidized bed reactor with powders of different oxidation levels. The temperature was slowly raised until a reaction between the titanium powder and reactive gas occurred. We find that there is linear dependence between the level of oxidation and the gate temperature at which the reaction occurs. After initial etching of surface oxide layer the reaction continues after the temperature is lowered significantly. The experimental finding correlates with nearly linear increase in formation energy of oxygen vacancy in TiO_x as oxygen content increases. Density functional modeling of the reaction at the surface of partly oxidized titanium as function of oxygen concentration will be presented.