Effect of Y2O3, La2O3 and ZrO2 dispersoid addition on ultra-high temperature stability of 95W-3.5Ni-1.5Fe heavy alloy

Abstract

In this work, the effect of three different oxide dispersoids (Y2O3, La2O3, ZrO2) addition on densification, phase, microstructure evolution and high-temperature stability has been investigated thoroughly and compared with that of 95W-3.5Ni-1.5Fe (wt.%) heavy alloy (WHA). The heavy alloys were prepared by powder metallurgy process and consolidated by conventional sintering at 1500 degrees C in hydrogen atmosphere. The oxide additives did not improve the densification, however, enhanced the hardness of the sintered heavy alloys. Upon exposure to ultra-high temperature (2300 degrees C) for 10 s, the base alloy suffered significant damage and experienced mass loss due to evaporation of W-oxide. On the other hand, Y2O3, La2O3 and ZrO2-dispersed heavy alloys exhibit pro-tective oxide layer formation. Furthermore, the XRD and FESEM analyses of the exposed surface affirm that no significant damage has incurred in the oxide dispersed WHAs despite identical experimental condition. Owing to the thermal stability of W-Y-O, W-La-O and W-Zr-O systems, the oxide-dispersed heavy alloys offer better structural stability at ultra-high temperature.