Employing preheating- and cooling-assisted technologies in machining of Inconel 718 with ceramic cutting tools: towards reducing tool wear and improving surface integrity

Abstract

This paper is motivated by the fact that machining of Inconel 718 involves rapid tool wear and poor surface integrity. We investigate the performance of ceramic cutting inserts in turning of Inconel 718 by virtue of two different assisted machining conditions, plasma preheating- and cryogenic cooling-assisted technologies. The plasma nozzle placed in front of the cutting zone is used to soften the materials before machining. The liquid nitrogen flow located in the cutting area is used to reduce the cutting temperatures in the contact area. The cutting experiments are set for reducing tool wear and improving surface integrity, including surface roughness and micro-hardness beneath workpiece surface. With these two assisted techniques, the tool wear including flank wear and notch wear and the surface microstructure including surface roughness and micro-hardness are assessed and compared with conventional machining. Tool wear reduction and surface integrity improvement can be obtained with these two assisted technologies in turning of Inconel 718 with ceramic cutting inserts. The main causation of notch wear of the ceramic cutting inserts may be the hardened layer beneath the surface. By comparing these two assisted cutting techniques with opposite effects on the cutting tool and workpiece, it has been found that the surface roughness is reduced by 50 %, the micro-hardness is smaller, and the tool life is extended up to more than 40 % over conventional machining.