Characteristics of Tungsten Prepared by Hot Pressing at High Pressure

Tungsten is a prime candidate material for the plasma-facing components of fusion reactors, thanks to its high melting point, high temperature strength, good thermal conductivity, high erosion resistance, etc. Yet, it has some limitations, mainly its brittle nature, difficulty of machining, and propensity to recrystallize at elevated temperatures. Among the approaches to the improvement of particular properties are alloying, dispersion strengthening, thermomechanical processing, and modifications to the sintering process. This study explores the possibility of combining fine powder size with ultra-high pressure to achieve significant densification at moderate temperatures during hot pressing. Two powder sizes and a range of temperatures from 1000 to 2000 °C were used, and their effects were observed. The resulting tungsten compacts were characterized for their microstructure, density, and mechanical and thermal properties. The high pressure enabled substantial densification already at relatively low temperatures, thanks to the plastic deformation of the powder particles. A significant degree of sintering, as manifested by the microstructural and property evolution, occurred however only at higher temperatures. The compacts exhibited brittleness, calling for further optimization of the method.