Influence of tool surface topography on the material transfer tendency and tool wear in the turning of 316L stainless steel

Abstract

The influence of tool surface topography on the initiation and build-up of transfer layers in the orthogonal turning of 316L austenitic stainless steel have been studied under well controlled conditions. Tool materials include CVD Ti(C,N)-Al2O3-TiN and PVD (Ti, Al)N-(Al,Cr)2O3 coated cemented carbide inserts prepared using different grinding and polishing treatments. Post-test characterization of the inserts was performed using high resolution scanning electron microscopy and energy dispersive X-ray spectroscopy.The results show that the transfer tendency of work material is strongly affected by the surface topography of the rake face. For both types of inserts, the initial transfer and the build-up of transfer layers are localised to microscopic surface irregularities on the rake face. Consequently, an appropriate surface treatment of the cemented carbide substrate before coating deposition and the as-deposited CVD and PVD coating can be used in order to reduce the transfer tendency and the mechanical interaction between the mating surfaces. Also, an improved surface finish was found to reduce coating wear and consequently the crater wear rate of the inserts investigated. This can most likely be explained by the reduced tendency to discrete chipping of coating fragments in the contact zone and the formation of a thin transfer layer composed of Al, Si, Ca, O with beneficial friction properties which are promoted by a smooth coating surface.