Effect of post-sintering heat treatment on porous tungsten in relation to sintering swelling

It has been shown recently that porous tungsten can be obtained at much lower temperatures T less than or equal to 1200 degreesC than those in conventional techniques where T greater than or equal to 2000 degreesC. This has been achieved by employing the concept of reactive sintering. The method makes use of the addition of Al, a low melting point phase which decreases the process temperature while acting as a potential sintering aid. As a result, higher homogeneity and uniform porosity distribution have been obtained. In this study, attention has been paid to the swelling phenomenon observed in porous tungsten upon post-sintering heat treatment. It has already been shown that swelling occurred in sintering porous tungsten by this alternative technique, and upon further heat treatment swelling instead of shrinkage became even more pronounced. This article explores the microstructural evolution upon post-sintering heat treatment on these parts. The relation between swelling and porosity for different tungsten particle sizes has been demonstrated. An attempt has been made to explain the possible reasons behind the changes in the porous structure. SEM has been a useful tool for the purpose of this study.