2 - The Refractory Carbides

Abstract

This chapter reviews the structural characteristics of the refractory carbides and discusses their classification and general features. Refractory carbides have a high melting point, arbitrarily fixed at > 1800 °C, and have a high degree of chemical stability. Only the interstitial and covalent carbides fulfill these two qualifications. The intermediate and salt-like carbides do not meet one or both of these conditions and cannot be considered as refractory, yet they are important materials. The refractory carbides are hard and wear-resistant, have high melting points, and are chemically inert. In a relatively short time, they have become major industrial materials with numerous applications such as cutting and grinding tools, bearings, textile-machinery components, oxidation-resistant gas burners, and many others. Three general and interrelated atomic characteristics play an essential part in the formation of carbides (and indeed of all compounds): (1) the difference in electronegativity between carbon and the other element, (2) the size of the respective atoms, (3) and the bonding characteristics of these atoms.