Parametric optimization of Al₂O₃-ZrO₂ (Y₂O₃) based self-lubricating composite cutting tool materials for turning operations using TOPSIS method

Zirconia Toughened Alumina (ZTA) is one of the best materials for cutting tools due to its exceptional mechanical properties. However, its poor tribological characteristics made it not suitable for dry machining applications. To overcome this problem, novel composite tools were manufactured in the current investigation by incorporating different proportions of self-lubricating elements such as NiCr, Ag, Mo, SrSO₄, and CaF₂. The performance of these developed self-lubricating cutting tools (SLTs) was examined thoroughly and compared with the base tool to select the best self-lubricating tool. The experimental runs were conducted with Taguchi L8 mixed-level orthogonal array. The TOPSIS method was used to convert the multi-decision criteria into a single-decision criterion for evaluating the performance measures like coefficient of friction (COF), cutting forces, i.e. (axial thrust, radial thrust, and main cutting forces), and surface roughness. The input parameters considered in this study are cutting speed (V), feed rate (f), and depth of cut (d). Turning experiments were performed on the AISI 4340 steel workpiece. The results showed the addition of SrSO₄ and Mo at 10 Wt.% and CaF₂ at 5 Wt.% produced a tool designated as SLT₄ in this study with superior mechanical and tribological characteristics. A self-lubrication layer developed on the cutting tool rake face was observed to improve the wear resistance of the tool and other key performance measures. The most optimal solution obtained from TOPSIS for SLT₄ is a cutting speed of 275 m/min, and the corresponding feed and depth of cut are 0.2 mm/rev and 0.1 mm, respectively. Further, a significant decrease in the outcomes of SLT₄ compared to the base cutting tool was observed at the optimum cutting parameters, indicating that SLT₄ is best ZTA-based tool. The COF reduced by about 45% and surface roughness by 66% compared to the base tool. The decrease in the corresponding cutting forces in the three orthogonal directions is 63.4% (main cutting force), 77.62% (radial thrust force), and 81% (axial thrust force), respectively.