In certain cases, even cemented tungsten carbide hardmetal tools are not sufficiently hard or wear resistant. This is where higher value diamond tools find their application. Many diamond impregnated tools contain tungsten and/or tungsten carbide in the metallic binder to improve their properties and cemented tungsten carbide is also used as the substrate for polycrystalline diamond (PCD) and polycrystalline cubic boron nitride (PCBN) products.
Additionally, large quantities of cemented tungsten carbide hardmetal are used to produce the synthetic industrial diamonds used in these diamond tools. As an example, of the estimated 4 billion carats (800 tonnes) of industrial diamond grit produced annually in the mid 2000s, around half came from China where more than 1,000 tonnes per year of cemented tungsten carbide were needed to produce the dies and anvils for the 7,000 high pressure/high temperature presses used in the diamond manufacturing process in that country. Worldwide, this figure is estimated as approaching 2,000 tonnes of cemented tungsten carbide for this application alone.
Construction materials, such as reinforced concrete, asphalt and masonry, often need to be cut, drilled, ground and/or polished. Decorative natural stone is processed by similar methods. A wide variety of diamond tools are used, including wire saws, reciprocating saw blades, circular saw blades, core drills and grinding wheels. To improve the wear resistance of the soft metal binders used to retain the diamonds (such as cobalt, copper, bronze, iron and alloys and mixtures thereof), tungsten metal, tungsten monocarbide or cast tungsten carbide are frequently added to the bond. This is particularly important for the processing of abrasive materials such as granite, marble and quartz-containing concrete.
Coarse diamond grit retained in metal binders acts as the cutting element of the bits. Cast tungsten carbide (W2C-WC eutectic), coarse tungsten metal (W) or tungsten monocarbide (WC) powder preforms are infiltrated with liquid metal (such as bronze or other copper-based alloys) to form the body of the bit and retain the diamonds.
The cutters consist of a layer of polycrystalline diamond integrally sintered to a tough tungsten carbide substrate under high pressure and high temperature; PDC cutters combine the high hardness and abrasion resistance of diamond with the impact resistance of tungsten carbide and provide a faster, more durable and cost-effective drilling.