Preparation for WC–Ni3Al Hard Metal by Vacuum Sintering

Abstract

WC–Ni₃Al hard metal of the composition for WC–25 vol% (Ni–24 at%Al–0.5 at%B) was prepared by vacuum sintering. The powder mixtures of WC, Ni, NiAl (Ni–50 at%Al) and B were treated by wet milling with a tumbling ball mill machine for 24 h or 48 h. The average particle size of the powder mixtures after wet-milling for 24 h and 48 h were 1.69 µm and 1.23 µm, respectively. These powder mixtures were press-moulded into the test-pieces and sintered in vacuum of (7∼9) × 10⁻³ Pa at various temperature for 1 h. The densities, microstructures and mechanical properties of the obtained sintered compacts were investigated. When 48 h wet-milled powder was used and the green compact was sintered at 1425°C for 1 h, the compact had relative density more than 99%, transverse rapture strength of 2.2 GPa and Vickers hardness of 1330 HV. On the other hand, using 24 h wet-milled powder, the sintered compact had lower mechanical properties than the compact of 48 h wet-milled powder because of low density and inhomogeneous microstructure. This Paper was Originally Published in Japanese in J. Jpn. Soc. Powder Powder Metallurgy 64 (2017) 615–620.