Effect of 10 at.% Nb Addition on Sintering and High Temperature Oxidation of W0.5Cr0.5 Alloy

The effect of 10 at.% Nb on the sintering and high temperature oxidation behavior of W0.5Cr0.5alloy was investigated. Elemental powder blends were made nanostructured by high energy mechanical milling, compacted and finally sintered under reduced atmosphere at 1790°C. The sintered samples were subjected to cyclic isothermal oxidation tests at 800°C to 1200°C in air. The experimental results shows superior sinterability and oxidation protection of W0.5Cr0.5alloy compared to pure W. Characterization of the oxide scales shows porous external W-rich oxide (WO3) formation which is not ideally suitable for oxidation resistance. On the other hand, W-Cr alloy with 10 at.% Nb shows the remarkable sinter densification (~98%) and oxidation resistance up to 1200°C. The oxide scale of the ternary alloy shows formation of stable Cr2O3, Nb2O5oxides and/or complex Cr-Nb oxide (CrNbO4), and there was no evidence of WO3formation in this case.