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Carbon fiber reinforced polymers (CFRPs) are becoming increasingly prevalent in the industries including automobile, aerospace, and military due to their light quality, high specific strength, high corrosion resistance, excellent thermodynamics performance, etc. However, these excellent properties easily result in intensive tool wear, short tool life, and reduced machining accuracy. Although ultrasonic vibration–assisted drilling (UVAD) was considered an effective drilling method to reduce tool wear, most reported studies focused on machining kinematics or mechanics, and very few studies systematically explored the tool wear behaviors in UVAD of CFRP. To fill this gap, this paper aims to investigate tool wear of high-speed steel (HSS) twist drill in UVAD of CFRP and compares these wear behaviors with those in conventional drilling based on the experimental observation of the worn drill morphologies. The effects of cutting parameters on tool wear were discussed with the special focus on the differences in tool wear between conventional drilling (CD) and UVAD. The observed wear behaviors can include abrasion, adhesion, oxidization, or the combination of them. The introduction of UVAD can effectively reduce the average width of tool flank wear with a maximum reduction of 13.0% when compared with CD. Both increased feed rate and decreased spindle speed can lead to decreased tool wear. The findings in this paper might offer guidance on the selection of cutting parameters for extending tool life in UVAD of CFRP. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The alumina-based ceramic cutting tools are a kind of promising tools used in machining of heat-resistant-super-alloys, such as nickel-based super alloy, due to its high wear resistance, low thermal expansion and good oxidation resistance up to above 1000�°C. Sharp temperature rise mainly caused by excessive plastic deformation as well as the friction in machining of nickel-based super alloys is considered to be the key for rapid tool wear, especially the notch wear, which is the predominant type of catastrophic failure mechanism for the round type ceramic cutting tools. In this study, the wear mechanism of alumina-based ceramic cutting tools during dry turning of Inconel 718 is experimentally investigated. Based on the observation of tool wear, an attempt by employing the hardened layer beneath the workpiece surface is made to explain the occurrence of notch wear. Consequently, a predictive model of notch wear depth considering the influence of work hardened layer is developed. Series of cutting tests are used to validate the proposed notch wear model, and the result indicates that the proposed model is feasible. The contribution of this work can guide the effective control of tool wear by reducing the work hardened layer through the optimization of processing parameters. [ABSTRACT FROM AUTHOR]