High temperature oxidation characteristics of Nb-10W-XCr alloys

The effect of Cr content on the microstructure and cyclic oxidation behavior of Nb-10W-XCr alloys with four different compositions has been investigated. Experiments were conducted in air at 900 degrees C and 1300 degrees C; the oxidation kinetics have been evaluated in terms of weight change per unit area with respect to exposure time. Alloy's microstructure consists of Nb solid solution phase regions surrounded by a network of NbCr2 Laves phase. A trend of improvement in oxidation resistance with increase of the intermetallic phase is observed at 1300 degrees C and oxidation kinetics follow a parabolic behavior. At 900 degrees C, alloys with higher Cr content exhibit higher oxidation rates than alloys with lower Cr content. The oxidation products are a mixture of CrNbO4, and Nb2O5 and the amount of each oxide present in the mixture is related to the intermetallic phase content. Results delineate the influence of microstructure and composition on the oxidation mechanisms of these alloys that represent a promising base for high-temperature intermetallic alloy development. (c) 2009 Elsevier B.V. All rights reserved.