Sintering of Cemented Carbides

Revised by Mack Greenfield and George Wolfe, Kennametal, Inc.

Cemented carbides consist of various mixtures of carbides and iron-group metals, such as tungsten carbide/cobalt, tungsten carbide/titanium carbide/tantalum carbide/niobium carbide/cobalt, or titanium carbide/molybdenum carbide/nickel. These materials typically are sintered to essentially 100% of theoretical density using a liquid-phase sintering process. The successful application of cemented carbides to high-stress operations such as metal cutting, oil well drilling, or metal forming dies depends on achieving low levels of residual porosity during sintering. Additionally, sintering must be controlled carefully to obtain desired microstructure and chemical composition.

Cemented carbides are used in many applications in the as-sintered condition. Frequently, the as-sintered surface acts as the critical wear/stress-bearing surface. In most metal-cutting applications, the tool is considered worn out when the wear scar depth exceeds 0.2 to 0.4 mm (0.008 to 0.016 in.). Consequently, control of surface properties is essential.

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