Tool wear resistance and interfacial degradation behaviour of PCBN inserts during high-speed turning of aluminium-grey cast iron bimetallic engine blocks

This study investigates the wear progression and interfacial degradation behaviour of polycrystalline cubic boron nitride (PCBN) cutting tools during high-speed turning of aluminium-grey cast iron (Al-GCI) bimetallic components. Machining experiments were conducted at a cutting speed of 1130.4 m/min with feed rates ranging from 0.14 to 0.18 mm/rev. At 0.14 mm/rev, PCBN inserts achieved stable tool life up to 442 cutting cycles while maintaining surface roughness below the industrial threshold (Rz ¤ 8 µm). Flank wear followed an exponential trend, and surface roughness evolution on both aluminium and GCI sides was accurately described using second-order polynomial models. SEM EDS analysis revealed dominant adhesive and abrasive wear mechanisms, with localized micro-chipping and tribo-chemical reactions at the tool-workpiece interface. Despite prolonged thermal mechanical exposure, the PCBN tools retained high microhardness (40.1-41.2 GPa), indicating strong structural integrity. An inversion in surface roughness was detected at the 200 cutting cycle, with the GCI side presenting superior surface finish compared to aluminium. This counterintuitive result, linked to wear land stabilization and adhesive transfer, highlights a previously unreported mechanism in bimetallic cutting. The findings provide a pathway for future applications in precision machining of hybrid components, where high tool reliability and controlled surface integrity are critical. © The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature 2025.