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Characteristics of cemented carbide

What is cemented carbide?

In a wide sense, cemented carbide refers to composite alloys binding the hard particles of carbides, nitrides, or carbonitrides of IVa, Va or VIa metals in the periodic table with iron-based metal. In particular, WC-Co-based alloys are widely used due to their excellent characteristics, and the general understanding is cemented carbide = WC-Co-based alloy. 1)

1High hardness

High hardness

Hardness increases dramatically as tungsten binds with carbon, resulting in high abrasion resistance.

2High strength

High strength

It is high in transverse rupture strength (bending strength), and delivers high reliability against forces in the bending direction.

3High rigidity

High rigidity

It has a high Young’s modulus (difficulty to bend), and excels in rigidity.

History of cemented carbide

While the history of the current cemented carbide goes back to the 1890s, the foundation for the current manufacturing method was established by K. Schroter in 1923, when he formed WC through the carbonization of W while reacting powders of W and C (carbon) in a hydrogen atmosphere, then added Co powder to the WC and sintered the mixture. In 1926, Friedlich Krupp in Germany industrialized cemented carbide in tools based on this technique, releasing products with the name Widia (Wie Diamant = like diamond). In 1928, the U.S. General Electric also released cemented carbide products, and research was begun by Toshiba, Sumitomo Electric Industries, and Mitsubishi Metal, each on their own, around 1928, to advance industrialization. Later it was found that alloys to which TiC, TaC, NbC and so forth was added, which have low reactivity against Fe, were better suited to steel cutting, and Krupp released the (WC-10% TiC-6%Co) alloy in 1931, establishing the foundation for cemented carbide as tools.

Then grain-size adjustment technology with addition of trace amounts of VC, TaC and so forth to WC was studied in a WC-Co2-based system, creating particulate hard metal type H in 1929, and a high-toughness alloy was developed with the use of coarse-grain WC and increase in the amount of Co, leading to the introduction of 15% Co alloy in 1932. At present, various improvements have been made in cemented carbide, which is used in cutting, abrasion resistance, impact resistance, mining tools and so forth. In recent years, the development of methods to form hard film coating on the surface of cemented carbide using the chemical vapor deposition (CVD) method or physical vapor deposition (PVD) method, and the special cemented carbide for coating has advanced, contributing to dramatic progress in the characteristics of tools.1)

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Characteristics of cemented carbide (typical example of WC-Co-based metal) 1)
Composition(mass%) Density
(Mg/m3
Hardness
HRA
Transverse rupture strength
(GPa)
Young’s modulus
(GPa)
Thermal conductivity
(W/m・K)
WC Co
100 15.7 92-94 0.3-0.5 720
97 3 15.1-15.2 90-93 1.0-1.2 668 88
95 5 14.8-15.0 90-91 1.6-1.8 620 80
90 10 14.3-14.5 88-90 1.5-1.9 584 71
85 15 13.8-14.0 86-88 1.8-2.2 548
80 20 13.1-13.3 83-86 2.0-2.6 500
75 25 12.8-13.0 82-84 1.8-2.7 467
70 30 12.3-12.5 80-82
100 8.9 179 71
1)The Japan Cemented Carbide Tool Manufacturer’s Association: Handbook on cemented carbide tools, 1988