High temperature oxidation behavior of W–Cr–Nb Alloys in the Temperature Range of 800–1200 °C

Abstract

A comparative study of high temperature oxidation behavior of the (W1−xCrx)90Nb10 (x=0.3, 0.5 and 0.6) alloys has been carried out at 800°C, 1000°C and 1200°C in static air. Microstructural study of the alloy samples conventionally sintered from the nanocrystalline elemental powders of W–Cr–Nb alloys shows the presence of a mixture of W-solid solution (Wss) and Cr2Nb phases. Comparison of the results of isothermal and cyclic oxidation tests shows the damage to be greater during the latter tests. The oxidation resistance during exposure at 800°C, 1000°C and 1200°C is found to be the highest for the (W0.4Cr0.6)90Nb10 alloy. Formation of WO3 appears to be responsible for poor oxidation resistance of (W0.7Cr0.3)90Nb10 alloy at 1200°C. On the other hand, growth of continuous Cr2WO6 scale appears to have significant role in protection against oxidation for the other two alloys at 1200°C. The formation of oxide scales containing Cr2WO6+NbWO5.5 and Cr2WO6+Nb2O5.3WO3 is found to be responsible for protection against oxidation at 800°C and1000°C, respectively.