Effect of iron oxide debris on the reciprocating sliding wear of tool steels

Abstract

The presence of wear debris in sliding contacts is often regarded as detrimental, since it can increase friction, induce abrasive wear, reduce actual lubricant film thickness and compromise lubrication systems. On the other hand, the presence of debris may be fundamental to the formation of a protective tribolayer, which can reduce friction and wear. This work investigates the effect of the presence of different iron oxides (F2O3 and Fe3O4) with different sizes on the unlubricated reciprocating sliding of tool steels. For that, sliding tests were carried out with and without the addition of iron oxides. The addition of Fe3O4 particles (larger and softer) resulted in friction (15%) and wear (95%) reduction. Two main factors seem to be responsible for friction and wear reduction when Fe3O4 particles were added into the contact. The first is the relative hardness of the debris in relation to the materials in contact. Since they are softer than the specimens and the counter bodies, they do not cause their severe abrasive wear, which is much more significant for the harder F2O3particles. The second is the relative size (RS) between the debris and the specimen surface topography. When RS is small, the debris get entrapped in the valleys of the specimen topography, thus not participating in the contact. On the other hand, for larger values of RS, the debris become active and therefore can participate in the formation of a protective tribolayer.