Abstract
Niobium metal was studied for its oxidation behaviour at different temperatures (800, 1000 & 1200 °C) and time (1, 3 & 5 h). The study revealed that Nb underwent oxidation forming pro-active Nb oxides with initial formation of meta-stable Nb12O29 which forms as an oxidisation resistant layer. However, formation of Nb2O5 from a meta-sable Nb12O29 did not act as protective layer as it exposed underneath to further oxidation leading to cracks. The oxidation kinetics of Nb shown a linear behaviour and the devised mathematical model using Deal Grove determined the thickness of oxide layers. The un-protectiveness of Nb2O5 was verified by the Vickers hardness (8.06 ± 0.4 GPa) and indentation fracture toughness (28.14 ± 0.4 MPa.m1/2) of material which decreased with increase in oxidation temperature.
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