Metal Transfer and the Wear Process

Experiments have been made with a radioactive, annealed steel pin rubbing against a hardened steel ring to compare the amount of wear with the amount of metal transferred from one surface to the other by welding. It was found that a layer of transferred matter from the pin was formed on the surface of the ring and that an equilibrium condition was reached in which the loss of wear debris from this layer was balanced by further transfer. By using a combination of radioactive and inactive test-pieces the rate of transfer to the ring in the equilibrium condition could be estimated and was found to be the same as the wear rate of the pin. There was no evidence that any loose wear particles were formed by direct removal of material from the pin. The transferred layer became oxidized due to frictional heating and it is concluded that the wear process consisted of three stages: transfer of metal, oxidation of the transferred layer, and the subsequent removal of the oxide to form a loose wear-product.