Influence of the initial powder characteristic on the densified tungsten microstructure by spark plasma sintering and hot isostatic pressing

The effect of powder characteristics on the sintering behaviour and microstructure of densified W by spark plasma sintering and post-hot isostatic pressing was investigated. W powder was prepared by ultrasonic spray pyrolysis of a W precursor and hydrogen reduction, and a commercially available powder was used for comparison. The synthesised W powders were present in the form of large agglomerates composed of nano-sized particles. The densified specimens prepared by ultrasonic spray pyrolysis showed lower relative density and larger grain size than when commercial powder was sintered under the same conditions. Microstructural observation for the specimen sintered using the powder of ultrasonic spray pyrolysis revealed that the relatively large pores are present along the grain boundaries. The observed microstructural features were discussed by sintering behaviour based on the effect of intra-agglomerate and inter-agglomerate pores in the initial powder on densification and grain growth.