Microstructure and cyclic oxidation behavior of W-Cr alloys prepared by sintering of mechanically alloyed nanocrystalline powders

Sintering and cyclic oxidation behavior of nanostructured W-Cr alloys having 30, 50 or 60 at.% Cr, prepared through mechanical alloying of elemental blends have been investigated. Relative density of 96-97.5% could be achieved by sintering at 1700 degrees C. X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy have shown the presence of W-rich and Cr-rich phases in sintered alloys. The oxidation resistance during exposure at 800 degrees C is found as the highest in the W0.4Cr0.6 alloy, while that at 1000 degrees C and 1200 degrees C appears to be the best for the W0.5Cr0.5 alloy. Relatively finer and more uniform distribution of the Cr-rich phase in microstructure of the W0.5Cr0.5 alloy appears to be responsible for its superior oxidation resistance. The Cr2O3 is found to be primarily responsible for protection against oxidation at 800 degrees C, while the formation of Cr2WO6 appears to have more significant role at >= 1000 degrees C. (C) 2012 Elsevier Ltd. All rights reserved.