Particle growth during the reduction of tungsten and molybdenum and activation of the sintering of these metals

Conclusions Particle growth during the reduction of tungsten and molybdenum powders and the shrinkage kinetics of these powders depend on two processes taking place simultaneously, namely, partial melting and vaporization of surface layers of the dioxides of these metals. During high-temperature reduction (> 1100°C), fine particles of tungsten and molybdenum dioxides are vaporized and redeposited on large particles; on the surface of the particles, a liquid phase may form, resulting in the generation of capillary forces which create a bond between separate particles. Melting of the oxides covering the surface of metallic tungsten and molybdenum particles promotes shrinkage during sintering, while conversely vaporization of the oxides inhibits the shrinkage of these metals.Translated from Poroshkovaya Metallurgiya, No. 9(69), pp. 34–38, September, 1968.