High Voltage Electric Discharge Consolidation of Tungsten Carbide - Cobalt Powder

Abstract

Today WC–Co composites are extensively used to enhance the wear resistance of various engineering components, e.g. cutting tools and dies. Cemented carbides are used throughout industry for high wear, abrasive applications as a result of their extreme hardness. Apart from their exceptional hardness, WC has other unique properties such as high melting point, high wear resistance, good thermal shock resistance, thermal conductivity and good oxidation resistance (Crowson & Chen, 1991). WC with ductile metals such as cobalt as a binding medium, which is known to be helpful in cementing fine WC particles, is used in bulk sintered forms. Matrices of ductile metals, such as cobalt, greatly improve its toughness, hence elimination the possibility of brittle fracture during operation. WC–Co composites are extensively used to enhance the wear resistance of various engineering components, e.g. cutting tools and dies. In this paper, we report the results of studying the macroscopic phenomena occurring under high voltage electric discharge consolidation of tungsten carbide cobalt powder (Grigoryev & Rosliakov, 2007). The methods of consolidation of powder materials, based on various techniques of transmission of electric current pulses through a powder under mechanical pressure, are widely studied in many research laboratories (Grasso1 et al., 2009). The interest in these methods was motivated by their ability to consolidate a large variety of powder materials to high densities within short periods of time, without having to increase grain sizes. They are especially important because make it makes it possible to obtain bulk nanomaterials (Groza & Zavaliangos, 2003; Kodasha et al., 2004). These methods include electric-discharge sintering (Raichenko, 1987), field-assisted sintering technique, plasma assisted sintering, spark plasma sintering (Groza & Zavaliangos, 2003; Munir, 2006; Olevsky, & Froyen, 2009) etc. The large number of these methods is related to the wide range of variation in the electrical parameters of the action on a powder. The increasing importance of these methods as a tool for consolidation of powders is demonstrated by the large number of papers published in the recent years (Figure 1). The efficiency of electric-pulse methods is determined by the multifactor effect on consolidated materials (Baranov et al., 2001). Specific features of plastic deformation of conducting materials under the electric-pulse effect on the microscopic level were considered in (Bataronov, 1999). To obtain materials with required properties, one has also