Cutting performance and failure mechanisms of TiB2-TiC-Al2O3 multi-dimensional gradient ceramic tool in intermittent turning of hardened steel

The TiB2-TiC-Al2O3 multi-dimensional gradient ceramic tool (MDGCT), whose composition varied in two directions, were designed and fabricated via hot-pressed vacuum sintering. The cutting performance, including cutting force, cutting temperature and chip morphology, and failure mechanisms of MDGCT with different orientation angles in intermittent turning of SKD11 hardened steel were investigated in comparison with the homogeneous commercial ceramic tool CC650 at different depths of cut and cutting speeds. And the distribution of thermal residual stress of MDGCT was investigated employing FEM analysis. Results showed that the multidimensional gradient ceramic tool with orientation angle of 15 degree (TT3A15) had the optimal comprehensive cutting performance. The main failure mechanisms of CC650 tool were chipping and fracture caused by crack propagation, while the crack propagation was effectively inhibited in the TT3A15 tool, and its failure mechanism was chipping at the tool nose. The contribution of multi-dimensional gradient structure of TT3A15 tool to the increasing residual compressive stress of minor cutting edge, the favorable anti-crack capacity of flank face and the heterogeneity of physical and mechanical properties of rake face were responsible for its optimal cutting performance.