The influence of the cutting tool microgeometry on the machinability of hardened AISI 4140 steel

Abstract

The performance of cutting tools can be drastically affected by cutting edge preparation i.e. the presence of a radius and/or a chamfer and their dimensions can alter cutting forces and temperature and, consequently, tool life as well as the surface quality of the machined component. The aim of this work is to investigate the machinability of AISI 4140 steel hardened to 40 HRC and 50 HRC when turning with coated tungsten carbide inserts with various microgeometries (brushed edges with distinct slopes). The following aspects were considered: cutting force components, cutting temperature and machined surface roughness. In comparison with the published literature, the novelty of the present work is related to the investigation of the machinability of a hardened steel by applying a large variety of customized non-commercial cutting edge geometries. Differently from other studies, the paper presents experimental results for temperature in the contact zone employing different cutting edge geometries. Moreover, in order to explain the results, an analysis of tool-workpiece contact zone is carried out for each edge geometry. The results indicated that cutting edge microgeometry affects mainly the feed and passive force components, while the cutting force, specific energy and cutting temperature are not drastically altered. Finally, no clear relationship between microgeometry and machined surface roughness was noticed, although irregular marks on the roughness profile were found when sharp edges were used (suggesting edge chipping) and evidence of side flow was noted when rounded edges were tested.