Self-lubricant “Mosaic” surfaces of type 316 austenitic stainless steel

Abstract

Mosaic coatings are composite surfaces tailored for specific tribological systems. This type of surface may be of great interest in improving the friction and wear behaviour of a base material. They may be manufactured by laser cladding of alternate lines of alloys of different composition [1]. Laser surface treatment offers the unique advantage of creating a locally controlled microstructure with specific phases. The poor sliding contact behaviour of stainless steels against itself could be improved by mosaic surfaces. In this study, the material choice was limited to an austenitic stainless steel 316L. Using the mosaic concept, surfaces were modified by the deposition of lines of an Epoxy+Graphite mixture. During sliding tests between a pin of the same type of stainless steel and the mosaic surfaces, a film transfer of Epoxy+Graphite mixture was observed outs the pin contact surface inducing a third body effect. The formation of a solid lubricant film was already effective for mosaic surfaces with 20% surface lines of a lubricating mixture Epoxy+Graphite 30%. From this microstructurale limit, the wear resistance increased for the mosaics surfaces, an increase associated with a decrease of friction coefficient. These types of mosaic surfaces equally delayed the seizure phenomena during contact with stainless steel 316L. Manufactured mosaic surface of alternate lines of lubricant mixture with different composition is a specific application of composite coatings. This type of coatings is able to induce an optimum tribologic behaviour during sliding contact by synergetic effect. The main interest in creating a self-lubricating contact is to avoid the use of oil lubrication. This development is important for future applications with respect to environmental considerations.