Experimental Investigation and Comparison of Flank Wear and Surface Roughness in Turning of AISI 4340 Steel using Ceramic Coated and Uncoated Carbide Inserts

Carbide inserts are most widely used for machining alloy steels which have wide applications in the industries. The present work is to investigate the influence of cutting parameters on surface roughness and flank wear in comparison with coated and uncoated carbide inserts. In this context, a single layer of titanium nitride (TiN) coating of 2μm thickness has been applied by the process of physical vapor deposition (PVD) on the carbide tool insert. The experimentation is carried out on AISI 4340 medium carbon alloy steel at multi-level cutting parameters. In this regard, a partial level mixed factorial was considered and an L18 orthogonal array is generated by design of experiments (DOE) in MINITAB15. Analysis of Variance (ANOVA) at a confidence level of 95% is used to analyze the effect of turning parameters on the responses. It is found that the type of insert is the most influencing parameter for both surface roughness and flank wear. However, a feed is the next influencing parameter on surface roughness and speed, feed on the flank wear. Scanning Electron Microscope (SEM) analysis was done for the coated and uncoated cutting inserts and the machined surface of the workpiece at the optimized cutting parameters obtained through the Main effects plots. It is known that TiN coating possesses high wear resistance, good thermal stability and low coefficient of friction, which results in the better performance of the coated inserts as compared to the uncoated inserts in all given machining conditions. The flank wear and surface roughness are affected by ploughing effect, burring and formation of built-up edges (BUE) which are found to be less in the coated inserts.