Cast Iron and the Self-Lubricating Behaviour of Graphite Under Abrasive Wear Conditions

Abstract

Cast iron is assessed as a self-lubricating material under sliding conditions. This is due to the graphite particles distributed in the matrix, which come out from their pocket, and form a tribofilm between the mating surfaces, and by which improve the tribological characteristics. In this study, the directionality and the interaction between the graphite and matrix material was investigated by micro-indentation and micro-scratch techniques. The results showed that the graphite is fractured and pushed out from the middle of graphite lamellas as a result of indentation. It was also observed that the graphite orientation below the surface intensely influenced the pushing out behaviour. For the graphite oriented toward the indenter position, the effect was more pronounced. Moreover, it was found that a scratch test can be used to investigate and explain the graphite pushing out tendency. The result was used to explain the directionality and the closing tendency of the graphite lamellas during sliding.