Chip control in the dry machining of hardened AISI 1045 steel

Hard machining has been recognized as an effective and efficient manufacturing process to replace the grinding of hardened material. To achieve a successful implementation of hard machining, chip morphology regulation is crucial since serrated chip morphology is desirable for breakability, collection, and automation. This study aims to address the critical factors in controlling the micro- and macro-chip morphologies in the hard turning of hardened AISI 1045 steel by using PCBN tool with chip breaker grooves to cover a wide range of machining parameters. Microscopic and macroscopic chip morphologies were measured, analyzed, and correlated with machining parameters and chip breaker. Experimental results demonstrate that high-speed machining is a substantial prerequisite for generating serrated chips by generating adiabatic shear bands and fracture bands, higher feed rate, and uncut depth are assistants to promote serrated chip when machining speed reaches its critical number. The bending force resulted from breaker grooves helps serrated chips break into 1∼3 cm lengths at macroscopic level. Periodic fluctuation of cutting forces along three directions was identified during the machining of hardened AISI 1045 steel at high machining speeds. This study suggests a feasible implementation of dry hard turning into industry applications.