The effect of consolidation parameters on the mechanical properties of binderless tungsten carbide

This paper discusses the effect of the process parameters on the mechanical properties of binderless pure tungsten carbide during a GPS (gas protection sintering) process. The result of experiments reveal that the mechanical properties of the material increases with raising the sintering temperature and extending the retention time; however a decreased hardness was observed as a result of abnormal grain growth under higher sintering temperatures. The results of XRD and EDS analyses confirmed the absence of brittle phases such as W2C or impurity phases in the microstructure. The optimized process parameters for GPS process are identified as: a mean particle size of 1.03 μm, a sintering temperature of 1860 °C and a retention time of 60 min; the resulting mechanical properties are: a relative density of 95.1%, a micro-hardness of 1718 kgf/mm2 and a fracture toughness of 5.97 MPa m1/2. The width of particles size distribution has a significant effect on the density and hardness of the sintered material however the width of particles size distribution is dependent on the original particle size. Finally, ultra-fine particles increase the chance of conglomeration and sub-micron structures. The conglomeration of ultra-fine particles hinders the filling of porosities during sintering and lowers the density and hardness of the material.

Research Highlights
► The binderless material fabricated is purely WC, without brittle W2C or other impurity phases.
► The width of particles size distribution after ball milling has a significant effect on the density and hardness of the sintered material.
► Ultra-fine particles increase the chance of conglomeration and sub-micron structures.
► The conglomeration of ultra-fine particles hinders the filling of porosities during sintering and lowers the density and hardness of the material.