Fabrication and Characterization of Various Nano-oxides Dispersed W-Ni Alloys by Mechanical Alloying and Conventional Sintering

Abstract

Nano Y2O3 and Al2O3 dispersed W-Ni alloys with nominal composition of W89Ni 10(Y2O3) 1 (alloy A), W89Ni10(Al2O3)1 (alloy B) and W89Ni10(La2O3)1(alloy C) were mechanically alloyed for 10 h followed by compaction at 0.5 GPa pressure with 5 min of dwell time and conventional sintering at 1400 °C with 2 h soaking time in Ar atmosphere with Ar flow rate of 100 ml/min. The microstructure of milled and sintered alloy was investigated using X-ray Diffraction (XRD), Scanning electron Microscopy (SEM), Energy dispersive spectroscopy (EDS),Elemental mapping and Transmission electron microscopy (TEM). Minimum crystallite size of 31.9 nm andmaximum lattice strain, dislocation density of 0.23%, 9.12 (1016/m2) respectively was found in alloy Aat 10 h of milling. Uneven and coarse particles at 0 h of milling converted to both elongated flake shape with at 10 h of milling. Bimodal (fine and coarse) particle size distribution is revealed in both the alloys and minimum particle size of 0.69 μm is achieved in 10 h milled alloy A. Evidences of formation of intermetallic phases like Y2WO6 in sintered alloy A, Al2(WO4)3 in sintered alloy B and La6W2O15 in sintered alloy C were revealed by XRD pattern , SEM micrographand EDS analysis for the alloys sintered at 1400 °Cand in addition to these intermetallics; evidence of Ni rich oxides was found for alloys sintered at 1500 °C. Minimum grain size of 1.50 μ m was recorded in sintered alloy A. Both faceted and spherical W matrix is evident in both the alloys which suggests occurrence of both solid phase and liquid phase sintering. Maximum % relative sintered density, Compressive strength and hardness of 85.29%, 1.674 GPa and 5.13 GPa respectively for alloys sintered at 1400 °C and 89.00%, 2.25GPa and 5.53 GPa for alloys sintered at 1500 °C was found in alloy A. Wear study at 20N force at 25 rpm for 15 min on ball on plate wear tester revealed that minimum wear depth (53.65 μm for alloy A sintered at 1400 °C and 10.9 μm for alloy A sintered at 1500 °C) and wear track width (272 μm for alloy A sintered at 1400 °C and 254 μm for alloy A sintered at 1500 °C) was found for alloy A as compared to alloy B.