Comparison of Ceramic and Coated Carbide Inserts Performance in Finish Turning of Hardened AISI 420 Stainless Steel

Abstract

Martensitic stainless steels have a high carbon amount that can be heat treated to increase their hardness. There are widely used in cutlery, needle valves, shear blades, dental and surgical equipment. In this study finish hard turning was performed on the AISI 420 stainless steel using ceramic and coated carbide inserts under dry cutting conditions. Depth of cut, feed rate, and cutting speed were selected as machining parameters, while surface roughness was chosen as machinability criterion. Taguchi L9 orthogonal array was selected for the design of the experiment to decrease the number of trials for reducing time and cost of manufacturing. The response surface methodology was utilized for determining a relationship among process parameters and output parameter. The analysis of variance results indicates that feed rate is the utmost factor on the surface roughness for both ceramic and carbide inserts with 86.56% and 80.57% contribution, respectively. The developed mathematical models for ceramic and coated carbide inserts are capable to predict surface roughness with 97.07% and 96.13% accuracy, respectively. Based on the desirability function and response optimizer of the RSM, 0.2 mm depth of cut, 250 m/min cutting speed, and 0.05 mm/rev feed rate were selected as optimum machining factors. Finally, the mean surface roughness for ceramic and coated carbide inserts calculated as 0.57 µm and 0.71 µm, respectively. Therefore, the ceramic insert exhibited better performance compared to the coated carbide insert.