Influence of surface particles of AKS-doped TBO on the NS-structure of tungsten wires

Abstract As a result of AKS-doping, submicron sized potassium-containing dopant particles are present on the surface of tungsten blue oxide (TBO). The aim of the present work was to study the effect of these surface particles on the non-sagging (NS) properties of doped tungsten. For this reason, hydrogen reduced tungsten powders, sintered ingots and 0.39 mm diameter wires were made from two starting materials: (a) doped TBO, (b) doped and subsequently H 2 O-washed TBO. The properties of the intermediate products that were made from the two blue oxides were comparatively investigated. The results indicated that during reduction, the potassium-containing dopant particles on the surface of TBO are trapped inside the growing tungsten crystals creating relatively large inclusions within the metal particles. It was concluded that these large inclusions in the metal particles generate large potassium pores in the sintered ingot from which long bubble rows are formed in the wire contributing to the development of a creep resistant NS-structure during recrystallization.