Effect of nickel additive on the grain growth of tungsten wire

The dependence of grain growth rate in tungsten on the amount of nickel additive was investigated to provide information on the role of nickel in tungsten-activated sintering. Undoped tungsten wires 250 μm in diameter, with various initial pain sizes, were sintered at 1400 °C with or without the nickel activator, and the change of grain size was determined by metallographic analysis. The addition of nickel to tungsten wire accelerated the grain growth as expected. However, the grain growth kinetics during tungsten-activated sintering seems to be different from that in the liquid-phase sintering of the W-Ni system; the rate constant for grain growth increased with increasing thickness of the nickel interlayers.