Effect of tempering on microstructure and machinability of AISI D3 tool steel in end milling with PVD-coated carbide tools

The present work highlighted experimental investigation on the effects of tempering on the micrography and machinability of AISI D3 tool steel, generally used for punches and dies in the stamping process, during end milling and dry milling operations. As expected quenching and tempering resulted in improving the mechanical properties. Hardness value in the as received material jumped from 29.1 HRc to up to 61.2 HRc according to the tempering temperature. Effectively as the latter increases, hardness decreases to 48.3 HRc. Relatively, microstructure analyses revealed that carbide particles merged and aggregated according to tempering temperature. EDS microanalysis confirmed the elemental composition of carbide and matrix zones in the microstructure of AISI D3 tool steel, showing a high degree of consistency in all samples examined compared with the initial and post-treatment states. Machinability was characterized by the tool life of TiAlN PVD-coated tungsten carbide inserts (grade GC1030) when milling on a conventional high-rigidity machine tool. The tests showed that increasing the tempering temperature significantly improves the material's machinability for an even better tool life ranging from 72 to 216 minutes at cutting speed 60 m/min.