The role of nitrogen in the oxidation behaviour of titanium and some binary alloys

The oxidation behaviour of titanium and of several binary alloys with aluminium (1.65, 3, 5, 10 wt.%), with chromium (1, 4, 11, 19 wt.%) and with silicon (0.25, 0.5, 1 wt.%), has been studied between 500 and 700 °C in oxygen (100 Torr) and in air (atmospheric pressure); oxidation times up to several thousand hours have allowed the role of nitrogen in the oxidation process to be examined. Kinetics results show, in all cases, better oxidation resistance in air than in oxygen. Morphological examinations and analytical results also show the marked influence of nitrogen on the structure, composition and mechanical properties of the oxide layers. A mechanism is proposed to explain the role of nitrogen in the oxidation process.