Initial Tool Wear Mechanism in Dry and Lubricated Turning of Inconel 718

Abstract

Tool wear mode and life are considered as critical machinability attributes. Three distinctive regions of tool wear, mainly known as initial wear, steady-state wear, and accelerated wear are understood to a large extent. The effects of cutting parameters on the initial tool wear have received less attention as compared to other two regions. Previous works by authors revealed that the cutting 4 s could be considered as the transition period between initial and steady-state wear in turning of Inconel 718 with coated carbide tools. It is believed that adequate selection of cutting parameters in initial periods of cutting operation may tend to optimize the entire tool life. Therefore, in order to assess the effects of cutting parameters on tool wear morphology and tool wear modes at transition time 4 s, various levels of cutting speed, constant levels of feed rate and depth of cut were used in dry and lubricated turning of Inconel 718, which is generally considered as one of the most difficult to cut materials. The scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) were used for tool wear measurements as well as microstructural evaluation of the tool wear mode. Based on experimental observations, despite the lubrication mode and cutting speed used, adhesion and abrasion were found in almost all cutting conditions. It is believed that abrasion is initially taken place and it caused removal of the coated layer of the tool. Following this phenomenon, the adhesion is also taken place. The variation of cutting speed does not widely change the tool wear results in transition time 4 s. Moreover, although negligible, higher flank wear results were found under dry conditions.