Exploring Enhanced Sintering Dynamics and Mechanical Integrity in WC-Base Composites Featuring Ultra-Low Proportions of Low-Activation Metals
Tungsten-based compounds are prized for exceptional properties crucial in nuclear fusion applications. Commonly cemented carbides can not be used in nuclear fusion applications due to the environmental, nuclear and high temperature limitations of cobalt and its alloys. This work proposes the use of small additions of low activation metals as alternative sintering aids allowing operation at higher temperatures while maintaining material integrity and efficiency. Composites of WC with additions of 5 and 10 vol% of Iron (Fe) or Titanium (Ti) underwent preparation through colloidal processing, involving also the addition of a small amount of Ni. Subsequently, the spark plasma sintering was employed determining the influence of the nature and amount of the metals in the sintering behaviour through the analysis of the dilatometric curves recorded during the process. Following the sintering process, our characterizations revealed the formation of two distinct types of composites depending on the starting metal: ceramic-ceramic for titanium additions and ceramic-metal for iron. The impact of binder content and the incorporation of small amounts of nickel on sintering behaviour, microstructure, and fundamental mechanical properties such as hardness, toughness, and bending strength was investigated. Nanoindentation mapping with 2D Gaussian analysis revealed consistent hardness and elastic modulus for the WC phase across studied composites, regardless of binder chemistry. In Fe-containing composites, Ni enhanced the hardness of constitutive phases by promoting a more favourable microstructure. Conversely, for Ti-containing composites, Ni promoted a denser TiC phase, sacrificing overall hardness in the mixed carbide and interface regions.