High Temperature Oxidation of V-5at.% Ti and V-10at.%Ti Alloys by Low Pressure Oxygen

Abstract

Oxidation behaviours of titanium-vanadium alloys containing 5 and 10at.% titanium have been investigated at temperatures ranging from 800 to 993K and oxygen pressures of 1.33 and 133Pa by means of a thermo-electrobalance, an X-ray diffractometer, an electron probe microanalyzer as well as metallographic techniques. Mass gain by oxidation mostly followed parabolic rate law. Oxidation resistance of vanadium has been highly improved, especially at low temperatures and high titanium concentration. Both alloys exhibited similar oxidation kinetics and scale structure. The activation energy for the parabolic oxidation was about 173kJ/mol, higher than that of vanadium. The oxide scale was a monolayer of VO₂ or (V, Ti) O₂ except for 993K and 133Pa. A very thin layer of TiO was formed at the oxide scale-alloy substrate interface, inside which was formed a very hard internal oxidation zone. The former appeared to retard the diffusion of oxygen into the substrate.