Cutting temperature effect on PCBN and CVD coated carbide tools in hard turning of D2 tool steel

This study compares the performance of CVD coated tungsten-carbide tools having an intermediate Al2O3 layer to low content PCBN tools in hard turning of D2 tool steel (52HRC). Results revealed that the coated carbide tool can outperform PCBN in machining the selected workpiece material within a certain range of cutting speeds (cutting temperature range). This is associated with tribo-film formation on the coated carbide tool surface. SEM and EDS were used to study the wear patterns of the used cutting tools. The tribo-films were investigated using the X-ray photoelectron method (XPS). The cutting temperature was measured using tool-workpiece thermocouple technique. The formation of the tribo-films was found to be highly-dependent on the cutting temperature and friction kinetics control at the tool–chip interface. Lubricious Cr–O tribo-films formed on the surface of the coated carbide tool, improving tool life at cutting speeds up to 100m/min, which relates to an average tool–chip interface temperature up to 930°C.