COMPARATIVE EVALUATION OF CBN, CERAMIC, AND CARBIDE INSERTS DURING HARD TURNING OF AISI 4340 STEEL USING TAGUCHI-BASED GRAY RELATIONAL ANALYSIS

In this experimental study, optimum cutting parameters were obtained in turning hardened AISI 4340 with three cutting inserts (ceramic, coated carbide, and CBN) using a gray relational analysis approach based on the Taguchi method. According to this approach, machining parameters such as workpiece hardness, insert type, cutting speed, feed rate, and depth of cut were optimized to minimize the cutting force components and surface roughness. Based on the 3D plots, the most effective insert type on cutting forces was ceramic, and the most effective insert type on surface roughness was cubic boron nitride. The developed regression equations can accurately predict the results, having a coefficient of determination greater than 98% for all responses. It was found that 51.93% depth of cut and 33.73% feed rate contributed to the responses based on the ANOVA results for a gray relational grade (GRG). With the confirmation experiments, improvement in GRG was found to be 0.387. Thus, this method can be applied in industries to improve the efficiency of the turning process.