Protection of titanium alloys against high temperature oxidation during closed-die forging: Structural analysis of the boro-silicate glass coating/Ti-6Al-4V alloy interfacial region by correlative imaging

We analyse herein the interfacial region formed between a borosilicate glass coating and Ti-6Al-4V alloy after a transient of 8 h at 1150 °C. The correlation of two optical and electron microscopy methods (Raman and Backscatter Electron Diffraction imaging) enabled an accurate description of this particular interface. This interface is composed of five different phases, namely Ti2O3, TiB2, TiB, Ti5Si3 and Ti6Si2B, and it proves to be protective against oxygen permeation. Finally, this study also enabled the development of a Raman database for Ti borides, silicides, and borosilicides, in part from experimental and more completely from theoretical (DFT computations) data.