An examination of a mild wear process

Abstract

A detailed study has been made of the wear of hardened high-speed tool steel rubbing on itself at a speed of 66 cm/s under loads of a few kilograms. Radioactive tracers, optical microscopy, reflexion and replica electron microscopy, and other methods of surface examination have been used. During the early stages of rubbing the main observable process is that of metallic welding and subsequent transfer of material between the rubbing surfaces. Earlier work has shown that under severe wear conditions a large proportion of the load may become supported on a single contact and this determines the scale of the welding and transfer processes. In the present experiments under mild wear conditions the load remains distributed upon many regions of contact. As rubbing proceeds, the wear rate increases but the scale of size of the wear process decreases. Eventually for well run-in surfaces the wear particles may be as small as a hundred ångstroms. The rubbing surfaces are then very smooth and the heights of the surface features are generally less than those of the aggregates of loose wear particles which are present on the surfaces. At this stage it is the loose debris which plays the predominant part in determining the character and rate of wear.