ADHESION THEORIES OF TRANSFER AND WEAR DURING SLIDING OF METALS

A regular solution model based on nearest-neighbor pair bonding is applied in this paper to predict the effect of adhesion on transfer and wear during the dry sliding of metals. A transfer event is treated as depending on interface separation and junction adhesion. The energies of a free surface and of a large-angle grain boundary are incorporated. The results indicate that transfer is favored over direct generation of wear debris particles. To predict relative transfer trends during early stages of sliding it is sufficient to concentrate on interface separation. After continued sliding, transfer material normally consists of contributions from both sliding components, and transfer trends will also be affected by junction adhesion. Based on an ideal solution model, transfer from the component with smaller surface energy is preferred. In addition, the transfer tendency of a single-phase binary alloy, and hence its wear rate, is suppressed if the alloying element has a larger surface energy. Although the adhesion models presented in this paper are rather simplified, reviews of published experimental data show that the above surface energy criteria can serve as a crude guide for predicting transfer tendencies for simple metal-metal and metal-binary alloy combinations. © 1990.