Effect of Ni addition on microstructure, mechanical and high temperature behavior of mechanically alloyed W-Nb

Abstract

The present investigation comprises the fabrication of tungsten (W) based alloys with nominal composition of W70Ni20Nb10 (alloy A), W75Ni15Nb10, (alloy B) (all in wt.%) by mechanical alloying (MA) in a planetary ball mill followed by sintering at 1500°C for 2 h in Ar atmosphere. The milled powders and the consolidated products have been investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Minimum crystallite size and maximum lattice strain of 45 nm and 0.42% respectively is achieved in alloy B. Maximum sinterability, hardness of 90.5%, 4.58 GPa (at 50g) respectively is achieved in alloy B due to finer crystallite size, higher surface energy and shorter atomic diffusion distance whereas maximum compressive strength of 2.14 GPa and minimum wear rate is achieved in alloy A owing to the formation of higher fraction of hard NbNi intermetallic phase. High temperature oxidation study at 900°C for 10 h reveals that lower oxidation rate is achieved in alloy A owing to lesser weight fraction of W and higher propensity of protective NiWO4 scale formation.