Comparative assessment of machining environments (dry, wet and MQL) in hard turning of AISI 4140 steel with CC6050 tools

Large quantities of coolant–lubricants are still widely used in the metal working industry, generating high consumption and discard costs and impacting the environment. This paper presents the evaluation of the performances of the various machining environments (dry, conventional wet and MQL technique) applied in hard turning of the AISI 4140 high-strength low alloy steel with coated mixed ceramic (CC6050) in terms of surface roughness, cutting force components, and tool wear. For this purpose, a number of machining experiments based on statistical four-factor (cutting speed, feed rate, depth of cut, and cutting radius) and hybrid-level factorial experiment designs uncompleted with a statistical analysis of variance were performed. The results indicate that the resulting cutting force obtained with the MQL machining process significantly improved when compared with other machining processes. For example: FRMQL ≈ 1.08 FRdry and FRwet ≈ 1.37 FRdry. Then, the RSM was utilized to define the optimal machining parameters. Finally, the ranges for best cutting conditions are proposed for serial industrial production.