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

• Published in: International journal of refractory metals & hard materials 2011-03, Vol.29 (2), p.188-201
• Main Author: Tsai, Kuo-Ming
• Format: Article
• Language: English
• Subjects: Ball-mill; Binderless tungsten carbide; Density; Global Positioning System; Hardness; Mechanical properties; Particle size distribution; Particle-size analysis; Phases; Satellite navigation systems; Sintered density; Sintering (powder metallurgy)
• ISSN: 0263-4368; 2213-3917
• DOI: 10.1016/j.ijrmhm.2010.10.006

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 W 2C 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/mm 2 and a fracture toughness of 5.97 MPa m 1/2. 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. ► The binderless material fabricated is purely WC, without brittle W 2C 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.