Influence of the cutting edge preparation method on characteristics and performance of PVD coated carbide inserts in hard turning

The use of cemented tungsten carbide inserts in hard machining requires proper coatings and edge micro-geometries. A suitable choice of these factors enables the reduction of cutting forces, the increase of tool life and the improvement of workpiece surface quality. However, the effects of the edge preparation method and coating process on the substrate properties influence the performance of the insert during cutting. In this context, the influence of two different edge preparation methods (plunge-face grinding and brushing) on the performance of TiAlN-coated cemented tungsten carbide inserts during hard turning is investigated. In general, higher values of surface roughness (Rz ≅ 0.3 μm) and edge chipping (Rk ≅ 4.5 μm) were observed for brushed inserts in comparison to the ground tools (Rz ≅ 0.2 μm, Rk ≅ 3.7 μm). Moreover, higher compressive residual stresses are induced by brushing in comparison to grinding (≅ 500 MPa against ≅ 400 MPa). In turning tests, cutting forces for the ground inserts are approximately 10% higher than for the brushed inserts. However, higher wear values are better related to lower compressive residual stresses in the substrate than to higher cutting forces.