Ultra High Speed Turning of Inconel 718 with Sialon Ceramic Tools

This paper explores the wear mechanisms of a Sialon ceramic tool in ultra high speed turning of Nickel-based alloy Inconel 718. Microstructures of the chips are also investigated. Stereo optical microscope and scanning electron microscope (SEM) are employed to observe worn surfaces of the tool produced by various wear mechanisms and morphological features of chips. In addition, the elemental compositions of wear products are evaluated by energy-dispersive X-ray spectroscopy (EDS). As a result of the study, wear mechanisms identified in the machining tests involve adhesive wear and abrasive wear. At the initial stage of cutting process, crater wear and flank wear are the main wear patterns. At the rapid wear stage, the SEM and EDS results showed that the adhered elements of Inconel 718 alloy on the tool rake face such as Ni, Fe and Cr accelerated the tool wear rate. Meanwhile, it was found that the chip morphology was serrated type under ultra high speed cutting condition, furthermore, the tendency of serration of the chip increased with the increase in cutting speed and feed rate.