Compound · WC

Tungsten carbide

Tungsten and carbon in a structure almost as hard as diamond and far tougher — the material nearly every cutting tool has an edge of.

Abrasive Toolmaking material

Tungsten carbide is what most things that cut other things are actually made of at the point of contact. It is nearly as hard as diamond, retains that hardness at temperatures that would soften any steel, and is stiff enough that a tool made from it barely deflects under load.

On its own it is also brittle, and a purely brittle cutting tool is useless. What is actually used is cemented carbide: carbide grains bonded together with five to fifteen per cent cobalt, sintered so the metal wets the grains and holds them in a matrix that can absorb a shock. The composite is a genuine engineering achievement — the hardness of a ceramic with enough toughness to be hit.

Uses

Machine tool inserts, drill bits for rock and for masonry, mining pick tips, saw teeth, dies for drawing wire, ball-point pen balls, snow tyre studs, and the surgical and dental instruments where an edge has to last.

It has a well-known second market in jewellery, where its scratch resistance is the selling point and its brittleness the recurring complaint: a carbide ring will not scratch and will shatter if struck hard, which is either a safety feature or a defect depending on who is describing it.

At the industrial scale, carbide is where most of the world's tungsten goes — and much of the world's cobalt binder with it, which quietly ties machine tooling to the same supply question as batteries.

History

It came out of a lamp factory. German researchers at Osram were looking for a cheaper way to draw tungsten filament wire — the diamond dies then in use were expensive — and produced a sintered carbide hard enough to replace them. It was commercialised as Widia, from *wie Diamant*, like diamond.

The consequence was a step change in what machining could do. Cutting speeds rose several-fold over the high-speed steels then standard, and much of twentieth-century manufacturing productivity rests on a material found while trying to make light bulbs more cheaply.

Medium confidence Weak evidence

How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.

How this connects

Where a connection has been confirmed by an outside reference, that reference is named beside it.

contains

Tungsten — element · half the atoms, and most of the mass — carbide is where the majority of the world's tungsten ends up Wikidata
Carbon — element · the other half of the formula, and what turns a hard metal into a very hard ceramic Wikidata

is used as

Abrasive — application · and as a cutting material, which is the larger use — carbide holds an edge at temperatures that would anneal any steel

is an alternative to

Diamond — mineral · as a cutting material: carbide is tougher and far cheaper, diamond is harder and cuts what carbide cannot
Osmiridium — alloy · as a wear-resistant tip. Carbide replaced it almost everywhere on cost, and osmiridium keeps the places where chemical inertness matters as much as hardness
High-speed steel — alloy · carbide is harder and cuts faster and shatters when the cut is interrupted; high-speed steel is what survives an imperfect setup, which is most work outside a production shop

succeeded

High-speed steel — alloy · in high-volume production cutting, where rigidity is available and speed is worth more than toughness

is produced by

Calcination — process · tungsten powder and carbon reacted at 1,500 °C, then sintered with cobalt as a binder into the tool the trade actually buys

Sources

Material World
Our own writing
Wikidata
Wikimedia Foundation · Creative Commons CC0 1.0 Universal (public domain dedication)