FUNDAMENTAL CONSIDERATIONS IN ADHESION, FRICTION AND WEAR FOR CERAMIC METAL CONTACTS

When a ceramic is brought into contact with a metal, strong bonds form between the materials. Adhesion and friction are strongly dependent on the ductility of the metals. The hardness of the metals plays a much more important role in adhesion and friction than does the surface energy of metals. The adhesion, friction, surface energy and hardness of a metal are all related to its Young's modulus and shear modulus, which have a marked dependence on the electron configuration of the metal. An increase in shear modulus results in a decrease in area of contact that is greater than the corresponding increase in surface energy (the bond energy) with shear modulus. Consequently, the adhesion and friction decrease with increasing shear modulus.