Tungsten carbide is extremely hard and great for cutting tool surfaces. Cobalt works very well with tungsten carbide and is a very ductile and shock absorbing. Without the cobalt, the tungsten carbide is prone to chipping off and fracturing when subject to quick load changes or high vibration in the worked on piece.
Specifying a large tungsten carbide particle size and a high percentage of Cobalt will yield a highly shock resistant (and high impact strength) part. The finer the tungsten carbide grain size (and therefore the more tungsten carbide surface area that has to be coated with Cobalt) and the less Cobalt used, the harder and more wear-resistant the resulting part will become. To get the best performance from carbide as a blade material, it is important to avoid premature edge failures caused by chipping or breakage, while simultaneously assuring optimum wear resistance.
a combination of tungsten carbide powder with powdered cobalt , a ductile metal that serves as a "binder" for the extremely hard tungsten carbide particles. The heat of the sintering process does not involve a reaction of the 2 constituents, but rather causes the cobalt to reach a near-liquid state and become like an encapsulating "glue" for the tungsten carbide particles . Two parameters, namely the ratio of Cobalt to tungsten carbide and the particle size, control the properties of the resulting "cemented tungsten carbide" piece.