Performance evaluation of the edge preparation of tungsten carbide inserts applied to hard turning

Owing to their inferior hot hardness in comparison with alumina-based ceramics and polycrystalline cubic boron nitride, the performance of coated carbide tools when turning hardened steels strongly relies on proper chemical composition and carbide grain size, together with adequate cutting edge preparation. This work investigates the effect of geometric parameters on the performance of cutting tools applied to turning of AISI 4140 steel hardened to 40 and 50 HRC, in terms of the components of the turning force and temperature. Additionally to well-established geometric parameters, such as the projection of the hone radius on the rake face (S-gamma), the projection of the hone radius on the clearance face (S-alpha), and the form factor K (ratio of S-gamma to S-alpha), a novel parameter is proposed, namely perimeter ratio (P), which represents the ratio of the perimeter of the modified cutting edge to the circumference of the standard honed edge. Moreover, the experimental results were compared with analytical and numerical findings in order to assess their effectiveness in predicting the components of the turning force and chip temperature. The results indicated that analytical modeling was capable to satisfactorily predict the variation of the force components with edge preparation, using as input the value of the corresponding experimental forces for the standard honed cutting edge. On the other hand, the numerical modeling was successfully applied to predict the components of the resultant force at the expense of higher computational effort. The cutting force was not drastically affected by edge preparation, whereas the feed and passive forces increased with P and S-alpha and the form factor K was not capable to provide a consistent relationship with both the feed and passive forces. Both the experimental and numerical temperatures of the chip and the numerical temperature at the tool-chip interface did not present a straightforward trend with regard to edge preparation.