Formation of a transfer layer at the tool-chip interface during machining

The formation of tribo-layers during machining is very common, especially when machining ‘free machining’ steels. Previous flow zone models of metal cutting have not included the shear strain rate distribution at the tool-chip interface, although the distribution directly affects contact behaviour. A new flow zone model is developed, based on the concept of the cutting interface, which occurs where the shear strain rate of chip deformation reaches a maximum and not where the speed of the chip is zero. The model is a dynamic model and it explains the dynamic contact behaviour between chip and the tool. The model enables changes and accumulation of changes in micro-machining to be related to tool wear and workpiece surface integrity. It will be able to produce information on changes in micro cutting conditions and the effect of change and the accumulation of such change on the tool wear and the surface integrity of the workpiece machined. The new flow zone model is used to interpret the tool wear processes occurring when machining three grades of austenitic stainless steel.