The removal of an Ni-activator from the Ni-activated sintered W-compact by high vacuum treatment

Abstract Nickel-activated sintered W-compacts with various porosities containing additives of 0.2 and 0.4 wt.% Ni were subjected to additional heat treatment in a vacuum better than 1.33 × 10 −2 Pa at 1400 °C in order to investigate the possibility of whether the added Ni, which will form a brittle phase, could be completely removed using an evaporation process. The added Ni-activator could be removed by optimum vacuum heat treatment up to a mean residual content of 0.07 wt.% which is approximately equivalent to the maximum solubility of Ni in W at 1400 °C. The evaporating behaviour of the Ni was strongly dependent not only on the porosity of the compact, but also on the type of pore, i.e. open or closed pores.