The Morphological Evolution of TiO2 Scale Formed on Various 1-D and 2-D Geometries of Titanium

Abstract : The purpose of this study is to experimentally quantify the multi-dimensional growth characteristics of the oxide scale formed on commercially pure titanium at 700 deg C in a flowing air environment. The geometries considered herein had characteristic dimensions that were appropriately sized to match the thickness of the oxide scale and were fabricated into shapes of solid and hollow cylinders and external and internal wedges. Scanning electron microscopy (SEM) image analysis was used to measure the oxide layer thickness and the Pilling-Bedworth ratio (PBR) as a function of time. An effective diffusion coefficient was determined from one-dimensional planar oxide thickness data and experimentally obtained PBR values served as the necessary input to a solid state diffusion model, which was modified to account for the volumetric expansion of the oxide.