Fabrication and characterization of nano-Y2O3 dispersed W-Ni-Nb alloys

The present research work comprises fabrication of nano Y2O3 ( < 50 nm particle size) dispersed W-Ni-Nb alloys with nominal composition of W79Ni10Nb10(Y2O3)(1) (alloy A), W78Ni10Nb10(Y2O3)(2) (alloy B) and W72Ni10Nb15(Y2O3)(3) (alloy C) (all in wt%) by mechanical alloying for 20 h and consolidation by conventional pressureless sintering at 1500 degrees C for 2 h. The mechanically alloyed powders and consolidated alloys have been characterized by X-ray diffraction, Scanning electron microscopy, Energy dispersive Spectroscopy and Transmission Electron Microscopy. Minimum crystallite size of 20.4 nm has been achieved in alloy C. The formation of NbNi intermetallic phases is evident in the sintered alloys. The bimodality of grains enhances with increases in Y2O3 addition. Maximum % densification of 93.38% and mean hardness of 5.59 GPa has been recorded in alloy C. The wear depth decreases with increase in Y2O3 content upto 2 wt%, however further increase results in enhancement of wear depth and wear loss. Preliminary investigation shows that Y2O3 dispersion upto 1 wt% is effective in providing enhanced oxidation resistance at 900 degrees C as compared to other alloys.