Activation Sintering of Tungsten and its Effect on Some Mechanical Properties.

The present work is concerned with improvements in the sintering properties of Tungsten. Two methods of "activation sintering" are studied, halogen activation and metallic activation. An example of the first is the use of hydrogen and bromine as sintering atmosphere. No significant increase in densification was noted, except for a moderate improvement at temperatures around 1400 C. However, some beneficial effects were observed, notably in the rounded shape of the pores and in lowering the oxygen content. This led to an improvement in mechanical properties. Metallic activation, mainly provided by nickel and palladium salts led to high densities at a sintering temperature of 1100 C but was accompanied by increased brittleness. This undesirable feature could be in part offset by controlling the amount of metallic activator and by some suitable subsequent heat-treatment. The two types of processes have been discussed seperately, some appropriate mechanisms are proposed to explain the results observed, and the theoretical implications are considered