OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 5 No. 4 2023 When changing parameters, one may observe a decrease in tool life parameters. Cutting speed can be considered as having the greatest impact on tool life, followed by feed and depth of cut. The highest tool life can be seen for MTCVD tools, followed by coated-microblasted and coated tools. This can be attributed to the thicker coating with an average thickness of 22 µm compared to the thinner coating with an average thickness of 3 µm. Further, the Al2O3 coating layer assisted to increase tool life by forming a protective aluminum oxide layer on the coated tool during machining, which has protected the tool from oxidation and the loss of cutting elements from the tool. Further, the TiCN layer of the coating provided higher adhesion between the coating and the substrate. Multi-objective optimization Researchers have made several attempts to optimize turning process parameters. However, limited studies optimized the turning of AISI 304 using coated, coated-microblasted, and MTCVD tools. The study uses a desirability function technique to optimize turning parameters to achieve minimal cutting forces, surface roughness, and maximum tool life. Using Eq. 16, each response variable (Ri) is converted into a desirability function (Di), and Eq. 17 transforms the optimization of multiple response variables into the optimization of a single desirability function (DM). The process variables and a variety of possible response functions are shown in table 7. min min min max max min max 0,1 if if ; 1, 0 if i i i i i R R R R D R R R R R R R ≤ − = ≤ ≤ − ≥ (16) ( )1 1 2 3 . n M n D D D D D = × × × − − − × (17) The one-sided transformation is used to transform each response Ri into its corresponding Di [23, 24]. By substituting all conceivable combinations and permutations of cutting parameters (around 10,000 data Ta b l e 7 Process variables and the range of response functions Process variables and responses Goal PVD-AlTiN coated (C) tool PVD-AlTiN coated-microblasted (CMB) MTCVD-TiCN/Al2O3 coated (MTCVD) Min. limit Max. limit Min. limit Max. limit Min. limit Max. limit Cutting speed (V) (m/min) Is in range 200 400 200 400 200 400 Feed (f) (mm/rev) Is in range 0.05 0.15 0.05 0.15 0.05 0.15 Depth of cut (d) (mm) Is in range 0.1 0.5 0.1 0.5 0.1 0.5 Tangential cutting force (Fc) (N) Minimize 24.5 128.3 11.9 209.9 15.1 220.4 Feed force (Ff) (N) Minimize 8.7 71.1 11.7 69.9 13.3 78.3 Radial force (Fr) (N) Minimize 7.8 21 7.7 30.4 14 34.6 Surface roughness (Ra) (mm) Minimize 0.20 1.46 0.21 1.47 0.24 1.59 Tool life (T) (min) Maximize 5.82 37.7 6.7 40.3 8.5 51.1
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