Cutting Fluid Effectiveness in the High-Speed Finish Machining of Inconel 718 Using a Whisker-Reinforced Ceramic Tool

This paper aims to investigate the effectiveness of cutting fluid during the high-speed face-turning of superalloy Inconel 718 using chamfered whisker-reinforced ceramic inserts. It addresses this topic by providing a comprehensive understanding of the machinability of Inconel 718 under both dry and wet conditions through analytical friction modeling and a detailed analysis of the chip formation process. Two new indexes, named the Area Function (<i data-eusoft-scrollable-element="1">AF</i>) and the Shape Function (<i data-eusoft-scrollable-element="1">SF</i>), were derived to assess the serration intensity of the chips. Particular attention was paid to the interaction between the cutting speed and the cutting fluid. The results showed that wet conditions promote uniform chip formation, more stable forces, a lower coefficient of friction, and the absence of notch wear. At low cutting speed (60 m/min) and dry machining results in high serration intensity (<i data-eusoft-scrollable-element="1">SF</i> = 0.7) and segmentation frequency (<inline-formula data-eusoft-scrollable-element="1"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline" data-eusoft-scrollable-element="1"><semantics data-eusoft-scrollable-element="1"><mrow data-eusoft-scrollable-element="1"><msub data-eusoft-scrollable-element="1"><mrow data-eusoft-scrollable-element="1"><mi data-eusoft-scrollable-element="1">f</mi></mrow><mrow data-eusoft-scrollable-element="1"><mi data-eusoft-scrollable-element="1">s</mi><mi data-eusoft-scrollable-element="1">e</mi><mi data-eusoft-scrollable-element="1">g</mi></mrow></msub></mrow></semantics></math></inline-formula> = 22.08 kHz) compared to the <i data-eusoft-scrollable-element="1">SF</i> of 0.4 and <inline-formula data-eusoft-scrollable-element="1"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline" data-eusoft-scrollable-element="1"><semantics data-eusoft-scrollable-element="1"><mrow data-eusoft-scrollable-element="1"><msub data-eusoft-scrollable-element="1"><mrow data-eusoft-scrollable-element="1"><mi data-eusoft-scrollable-element="1">f</mi></mrow><mrow data-eusoft-scrollable-element="1"><mi data-eusoft-scrollable-element="1">s</mi><mi data-eusoft-scrollable-element="1">e</mi><mi data-eusoft-scrollable-element="1">g</mi></mrow></msub></mrow></semantics></math></inline-formula> = 19.69 kHz in wet conditions. The segmentation frequency increases significantly with cutting speed, reaching 71.03 kHz and 63.32 kHz at a cutting speed of 225 m/min for dry and wet conditions, respectively. It was also found that the rate of increase in the tangential force was lower (20.49 N/s) when using cutting fluid at a high cutting speed (225 m/min) compared to dry conditions (27.37 N/s).