The effect of niobium on the oxidation behaviour of titanium in N-2/20% O-2 atmospheres

A systematic study on the isothermal oxidation of Ti-based materials, i.e. pure Ti, Ti-4at.%Nb, and niobium implanted Ti, was conducted in order to ob tain more insight into the role of small amounts of niobium on the oxidatio n of niobium-containing intermetallic alloys. Examinations were performed b y thermogravimetry and by studying the surface morphology, structure and co mposition of the oxidation products. Hardness measurements were made to qua ntify the amount of dissolved oxygen in the metallic matrix. Oxidation expe riments performed in dry and humidified nitrogen/oxygen atmospheres at 800 degrees C showed that the presence of niobium not only significantly reduce d the growth of titania, but also significantly reduced the influence of wa ter on the oxidation behaviour of Ti. This beneficial effect was explained by the formation of a continuous nitride layer, already during the initial stage of the oxidation, at the scale/substrate interface, induced by the pr esence of small amounts of niobium. (C) 2000 Elsevier Science S.A. All righ ts reserved.