This group of Cemented Carbides contains WC and Co only (i.e. two phases) and a few trace elements. These grades are classified according to their cobalt content and WC grain size.

The grades with binder content in the range 10-20% by weight and WC-grain sizes between 1 and 5 μm have high strength and toughness, combined with good wear resistance.
The grades with binder contents in the range 3-15% and grain sizes below 1 μm have high hardness and compressive strength, combined with exceptionally high wear resistance.

 
Microstructure of γ-phase grade

The Sandvik grade program also includes WC-Co grades which utilize a range of ultra-fine WC grain sizes (< 0.5 μm). With such fine, uniform grain sizes, a unique combination of hardness, wear resistance and toughness can be achieved.

The grades of Cemented Carbides in this group contain WC and Co as the main elements, although small additions or trace levels of other elements are often added to optimize properties. These grades are classified according to their Cobalt content and WC grain size and are often called the "straight grades". They have the widest range of strength and toughness of all the Cemented Carbide types and this is in combination with excellent wear resistance.

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Cemented carbides are sintered products of one or more carbide powders - usually tungsten carbideas the main component _ with a metallic binder (cement), preferably cobalt. Due to the extremehardness  of tungsten carbide and tungsten carbide' based smter alloys,  about 90 % of the globalmanufacturing volume is used for the manufacture of tools.

Tungsten carbide is applied to improvethe wear resistance of moving parts in machines like rolls and balls, of bearings, and nozzles,cutting and drilling tools, and mining equipment. Tungsten carbide cemented with copper or silveris used for electrical contacts and in fuel cells. Since most cemented carbides contain tungstencarbide, which gives them their extreme hardness and their high specific gravity, these alloys arereferred to as hard metals and are often also termed "tungsten carbide". The global production ofhard metals was approximately 20 000 tonnes in 1985 (Tulhoff, 2000).

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The Cemented Carbides are a range of composite materials, which consist of hard carbide particles bonded together by a metallic binder.

The proportion of carbide phase is generally between 70-97% of the total weight of the composite and its grain size averages between 0.4 and 10 μm.

Tungsten carbide (WC), the hard phase, together with cobalt (Co), the binder phase, forms the basic Cemented Carbide structure from which other types of Cemented Carbide have been developed. In addition to the straight tungsten carbide – cobalt compositions – Cemented Carbide may contain varying proportions of titanium carbide (TiC), tantalum carbide (TaC) and niobium carbide (NbC). These carbides are mutually soluble and can also dissolve a high proportion of tungsten carbide. Also, Cemented Carbides are produced which have the cobalt binder phase alloyed with, or completely replaced by, other metals such as iron (Fe), chromium (Cr), nickel (Ni), molybdenum (Mo), or alloys of these elements.

There are three individual phases which make up Cemented Carbide. In metallurgical terms, the tungsten carbide phase (WC) is referred to as the a-phase (alpha), the binder phase (i.e. Co, Ni etc.) as the b-phase (beta), and any other single or combination of carbide phases (TiC, Ta/NbC etc) as the g-phase (gamma). Other than for metal cutting applications, there is no internationally accepted classification of Cemented Carbides.

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Tungsten carbide is manufactured by direct carburization of tungsten with carbon (Roempp, 2003).Mixtures ot metal and carbon DiaCK or grapmte are tieated ai a iemperarure of 140u - L v-vacuum or under hydrogen (Tulhoff, 2000):vv+c．)WC.When heating a mixture of tungsten and carbon in a car'oon tube or high-frequency furnace to ca.800 0C, cast tungsten carbide is o'otained (Gmelin, 1993), However, most tungsten carbide is so'I"das powders with distinct ranges of grain sizes (Tulhoff, 2000),
Purity and gYain size determine the physical properties and the technical applicability of tungstencarbide. Since milling changes the chemical composition and the shape of the grains, coarsepowders of tungsten carbide can not be milled to obtain fine-~ained powders.

Instead, to obtain theiesired industr'ie'al' product, the particle size of the raw materials is carefully selected. The grain sizeof the product is also irrfluenc'ed by manufacturing parameters like temperature, reaction tiffie,resence of humidity and hydrogen.'Typica/ production lines start from tungsten ore (W, Nb, Fe-oxides), tungsten scrap, scheelite (Ca\V04), tungstic acid (H2W04), and ammonium paratungstate《NH'4)10W'1'2S04" X 5 H:O). Typica/ intermediates are yellow~(W03), blue (appro}cimatciY  W4Ullj,a'nd brown tungsten oxide '(W02).

There are several m~t'hods for the manufacturin9 0f the technicaltungsten carbide powders (Tu/hoff, 2000): Tungstic acid powder is reduced to tungsten by hydrogenat 750 0C. The metal particles are carburized at 1400 0C. This method is applied for fine powderswith an average grain size of l llm.

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