Frictional Heating and Its Influence on the Wear of Steel

Abstract

High frictional temperatures during the dry or imperfectly lubricated rubbing of steel produce gross structural changes and intense hardening of the surface layers. In consequence of these changes the wear time curve shows a marked inflexion, the wear rate of soft steel on soft steel diminishing by more than an order of magnitude as the hardened skin develops. The protective layer establishes itself more readily as the carbon content of the steel increases, a feature explained by the ease with which eutectoid pearlite transforms to austenite, and thence to martensite, during the rapid temperature cycle. By simulating the hot spots during wear by the thermal action of electric sparks, the hardness change is shown to be intensified by nitrogen or carbon absorbed from the atmosphere or lubricant.