Material side flow in finish turning of hardened steel with ceramic tools

Turning of hardened steel using ceramic tools is performed as a finishing operation. The occurrence of plastic side flow affects the machined surface quality. This paper studies the material side flow and the plastic deformation of the ceramic tool during the hard turning process. The experimental results show that material side flow depends on the cutting conditions and the changes in the tool geometry. These results reveal that plastic deformation of the ceramic cutting edge occurs, triggering surface roughness deterioration, and eventually, edge fracture. The thermal and mechanical stress distributions on the ceramic cutting edge, determined by a finite element analysis, are comparable with the Traverse Rupture Stress value for ceramic materials. These stresses, combined with high temperatures, cause plastic deformation. A three dimensional model was developed to calculate the workpiece stress field during machining. The results showed that the plastic flow was predominantly initiated in the vicinity of the cutting area by the cutting forces and thermal stresses and expanded towards the finished surface.