Machinability assessment of inconel 718 by factorial design of experiment coupled with response surface methodology

Machinability assessment of nickel base super alloy (inconel 718) in turning operations has been carried out using coated and uncoated carbide inserts under dry conditions. Inconel 718 is one of the most difficult-to-machine materials because of its low thermal diffusive property, high hardness, and high strength at high temperature. This paper describes the development of response models (tool life, surface toughness, and cutting force) for turning inconel 718 utilizing factorial design of experiment and response surface methodology. First-order predictive models covering the speed range of 10-33 m/min and second-order models within the speed range of 7-45 m/min have been developed at 95% confidence interval. The adequacy of the different response models have been judged by analyzing the variance. Based on the response models, contours have been plotted in speed-feed planes. In some cases dual response contours (response and metal removal rate) have also been presented. From the plot of dual response (surface roughness and metal removal rate) contours, one can choose cutting parameters for higher metal removal rates without sacrificing surface finish. Dual response contours of tool life and surface roughness have also been presented. For a given surface finish. these contours help to predict the cutting conditions for maximum tool life. (C) 1999 Elsevier Science S.A. All rights reserved.