Air Oxidation Behaviour of a Ti-6Al-7Nb Alloy

Abstract

Air oxidation behavior of a Ti6Al7Nb alloy was examined over the temperature range of 873 –1173 K for different time intervals ranging in between 12 and 72 h. The rate of oxidation evaluated according to the weight gain measurements, fitted parabolic kinetics by yielding oxidation activation energy of 226 kJ/mol. Rutile and anatase modifications of TiO2 formed on the surface as the result of air oxidation. Oxidation temperatures higher than 923 K encouraged rutile formation rather than anatase. As temperature of oxidation was increased, the thickness of the oxide layer increased. Thicker oxide layer provided higher surface hardness and better protection against a corrosive media (5 M HCl solution) was provided.

Characterization of thermally oxidized Ti6Al7Nb alloy for biological applications

“…Our TO studies conducted in an air circulating furnace over a temperature range of 600°C to 900°C for different time intervals ranging from 0.5 to 72 h also confirmed better oxidation resistance of Ti6Al7Nb alloy [26] than that of Ti6Al4V alloy [27]. Previously, vanadium and niobium were classified as detrimental and beneficial alloying elements, respectively, according to their effects on oxidation resistance of titanium alloys [28].…”

An Overview on Surface Hardening of Titanium Alloys by Diffusion of Interstitial Atoms

“…Further dissolution of oxygen in titanium renders α-Ti stable and β-Ti disappears. Thermal oxidation (TO), which is based on diffusion of oxygen atoms into titanium and its alloys at high temperatures in any oxygen containing ambient, produces a graded surface consisting of titanium oxide as the compound layer and an oxygen enriched α-Ti solid solution as the diffusion zone (DZ) [6][7][8]16,[19][20][21][22][23][24][25][26]. A cross -sectional optical micrograph of the TO treated Ti6Al4V alloy is presented in Fig.…”