Comparative Study of Nano ZrO2 and Nano Y2O3 Dispersed Mechanically Alloyed and Conventionally Sintered W-Ni-Nb-Ti

Abstract

Nano Y2O3 and Nano ZrO2 dispersed W based alloys with nominal composition of W79Ni10Ti5Nb5(ZrO2)1 (alloy A) and W79Ni10Ti5Nb5(Y2O3)1 (alloy B) (all in wt.%) were synthesized by mechanical alloying in a high energy planetary ball mill followed by compaction at 500MPa and conventional sintering at 1100°C, 1300°C, 1500°C for 2 h. Various characterization of the milled powder and consolidated products such as X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Energy dispersive spectroscopy (EDS), Transmission electron microscopy (TEM), Differential scanning calorimetry (DSC) was carried out. Crystallite size of 14.7 nm and 32.1 nm was achieved in alloy A and alloy B respectively and recorded lattice strain was 0.54% and 0.51% respectively. XRD and SEM study for sintered samples confirms the presence of NiNb, Ni3Ti and NiTi2 intermetallic compounds and formation of intermetallic phases increases with increase in sintering temperature in both the alloys. The % of sintered densification improves with increasing in sintering temperature for both the alloys whereas alloy A exhibited higher density as compared to alloy B at all sintering temperature. Maximum % of sintered density of 91.5% was recorded in alloy A at 1500°C against alloy B. Alloy B showed superior hardness at 1500°C temperature 5.895 GPa as compared to alloy A, and the hardness drops with decrease in sintering temperature for both the alloys. Wear test results at 20N and 30N load showed improved wear resistance of alloy B at all sintering temperature as compared to alloy A. High temperature oxidation at 1000°C for 10 h showed superior oxidation resistance in alloy B at 1500°C as compared to alloy A.