On the wear mechanisms of ceramic round inserts in high-speed turning of Inconel 718

Abstract

Inconel 718 is extensively used in various fields due to its excellent thermal and mechanical properties, combined with high resistance to corrosion and oxidation. In addition, the alloy retains these properties over a wide temperature range, up to around 750 °C, making it suitable for high-temperature applications. However, machining Inconel 718 is challenging as the above properties are coupled with a very low thermal conductivity, which reduces the heat dissipation in the cutting zone, resulting in significant tool wear. Ceramic tools, characterized by very high hot hardness, are being extensively used to mitigate this effect; in addition, inserts with a round geometry can alleviate the issue of the ceramics' low toughness. In this study, the wear behavior of two round advanced ceramic inserts, namely SiC whiskers-reinforced alumina and Bidemics™ ones, was investigated using a conventional coated carbide tool (WC) as the baseline for comparison. The inserts' characteristics were evaluated as constitutive elements, microstructure, surface topography, hot hardness, thermal conductivity, and wettability. A turning campaign was carried out to investigate the inserts' performance in terms of material removal rate, flank wear, cutting forces, and machined surface finish. The inserts' wear modes were evaluated based on their distinctive round geometry, revealing that the highest wear occurred in the central zone of the flank face regardless of the inserts' material. Notch wear and chipping were observed as the primary wear modes on the leading and trailing cutting edges of the Al 2 O 3 +SiC w and Bidemics™ inserts, respectively. It was found that the Bidemics™ inserts outperformed both the SiC whisker-reinforced alumina and the coated WC ones, demonstrating that Bidemics™ as insert material is an effective solution in machining Inconel 718 due to its high hot hardness and thermal conductivity.

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