Surface and Interfacial Energies in Systems of Certain Refractory-metal Monocarbides with Liquid Cobalt

Abstract

ONE technique for the determination of surface energies of solids is the method of multiphase equilibrium^1,2. This method has been used in the past to measure the surface energy of the compounds UO₂ (ref. 3) and UC (ref. 4), as well as that of metals². Briefly, the method involves the measurement of certain equilibrium interphase angles, namely (i) the angle of contact, θ, of a suitable liquid on the surface of the solid in a suitable atmosphere; (ii) the dihedral angle, φ, formed in a system of grains of the solid dispersed in the same liquid, between the solid–liquid interfaces of adjacent grains in contact; and (iii) the grain-boundary groove angle, ψ, formed between adjacent grains at the solid surface. It can be shown that these three angles are directly related to the energies of the interfaces that form them. If the angles are measured and the surface energy of the liquid, γ_LV, is known, then the energy of the interface between the solid and the liquid, γ_SL, and the grain boundary energy, γ_SS, as well as the surface energy of the solid, γ_SV, can be determined. The applicability of this method depends on the existence of a liquid which readily forms the relevant equilibrium angles but which does not react chemically with the solid. During investigations of several cemented carbide alloys, it has become apparent that the systems of certain carbides with liquid cobalt are suited to the measurement of the surface and interfacial energies by this method; the results of such measurements are presented in this communication.