PROPERTIES AND END USES OF CEMENTED CARBIDES *

The end uses of cemented carbides are probably more diverse than those of any other powder metallurgy product. The commonest use is to resist wear, but so many widely different wear mechanisms are encountered in practice that different grades of carbide must be produced to resist attrition, chemical erosion, micro chipping, and diffusion wear. In metal cutting high temperatures are frequently encountered, generally under conditions of severe temperature gradients so that high-temperature hardness and strength and a resistance to thermal stresses and thermal shock must be provided. Tools for operations such as wire and bar drawing, cold extrusion and cold heading require an optimum combination of hardness and strength. Generally such tools also require a very high quality of surface finish. Special measures are desirable to minimize porosity, and fortunately these also give considerable benefit from improvements in strength. Tools for mining applications show similar diversity in the properties required. The percussive rock drill in particular encounters a wide variety of service conditions and is an application where strength is often a limiting factor. Other tools such as those used for certain coal mining applications are less critical in their demands, and economic factors can influence the choice and quality of product. The paper reviews the properties and wear mechanisms that occur with the commoner uses of cemented carbide alloys. and describes how grades are ‘tailored’ to suit various applications.