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Information on tungsten: sources, properties and uses

Extra Coarse to Near-Nano

The history of cemented carbides is the history of a steadily widening range of available tungsten carbide (WC) grain sizes for processing.  The main reason for this widening of the spectrum of WC grades is that besides those variations achieved by the cobalt content, the properties, such as hardness, toughness, strength, wear resistance, modulus of elasticity, etc can be widely varied by means of the WC grain size.  The finer the cemented carbide, the harder is the material, and contraiwise.

In industry, the term extra-coarse is used for cemented carbides with mean WC grain sizes of >5µm (for comparison: the size of typical bacteria is in the range of 1-5µm), which can still be called fine-grained materials, particularly compared to competitive materials, such as steels or ceramics.  Such tools are used in cases where a high abrasion resistance is demanded besides a good impact strength, for example, in surface mining or hot rolling of metals (typically containing 6 to 30% wt % Co, or alternatively Co/Ni/Cr).

In contrast, the term near-nano describes a material with WC grain sizes below 200nm (0.2µm).  They are used where an extreme wear resistance of the tool is mandatory for an application, for example, water jet nozzles with water pressures up to 4,000 bar (tool hardness: HV10 : 2,800).

Fine grained cemented carbides have been the fastest growing segment of the cemented carbide industry over the last twenty years, due to their high strength (compressive strength up to 8,000 MPa), hardness and microstructural uniformity at still moderate toughness.  They are used for round tools (drills, threaders, reamers, routers), tools for electronic industries (micro tools), as wear parts, chipless forming tools, circular shearing tools, wood machining tools, for can tooling and, more recently, also in the form of a variety of coated and uncoated metal-cutting inserts of complex geometries.

© 2011 International Tungsten Industry Association
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