Comparative performance studies of turning 4140 steel with TiC/TiCN/TiN-coated carbide inserts using MQL, flooding with vegetable cutting fluids, and dry machining

This paper presents an experimental machining study of turning medium carbon alloy steel 4140 on Haas CNC turning center with TiC/TiCN/TiN-coated carbide inserts under different lubricating conditions. Cutting speed and feed rate were controlled at three different levels while a constant depth of cut is employed throughout the entire experimental study. The cutting fluid used in the study was produced from a genetically modified soybean oil and is hence biodegradable, renewable, less toxic, and sustainable to the environment. The three lubricating conditions tested in the study were dry, minimum quantity lubrication (MQL) (40 mL/min), and flood (1.3 L/min) conditions. With cutting speed and feed rate being control variables and cutting lubricate condition as noise factor, in total, 27 experimental runs were conducted according to Taguchi's L-9 (3(4)) orthogonal array. Statistical analysis using one-way ANOVA found that feed rate is a significant factor impacting surface roughness while cutting speed does not impact tool wear due to the range of speeds selected and use of coated insert. This study also concludes that dry condition generates the best result as the applications of cutting fluid in flood or MQL format did not generate significantly better surface roughness and lower tool wear. This implies that cutting fluids may be eliminated with careful selection of cutting parameters and tooling materials.