OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 1 2024 Fig. 3. Eff ect of feed rate on surface roughness at diff erent cutting speed and depth of cut for all materials using TiAlN-coated tool a b c d e the material becomes more ductile when cutting and a smoother cut is possible, which leads to better surface quality [11]. The minimum Ra is achieved by increasing Vc from 240 m/min to 340 m/min and doc from 0.8 mm to 1 mm, as shown in fi gure 3 c–e, since at higher Vc the strain rate in the shear zone is expected to be high, which will lead to an increase in temperature [2]. As Vc and f increase, the temperature increases because the heat dissipation time decreases and the larger chip-tool contact area increases friction. Vc and doc are signifi cant factors in increasing tool temperature for SS 316 and SAE 8620. Ra decreases due to increasing strain rate [24]. Figure 4, a–e clearly shows that higher Vc provides good surface roughness for almost all materials. However, as f and doc increase, the surface roughness increases fi rst for SS 316 and then for Al 380. EN 8 shows even better results due to low heat generation in the cutting zone, which maintains tool shape stability. Since the thermal conductivity of SS 316 is lower compared to other materials, it becomes more ductile during cutting due to increased temperature, and a smoother cut is possible due to better surface quality [2]. Ra was found to be the worst when machining Al 380 and was superior to SS 316 and SAE 8620. The sticking of Al 380 material results in a rough surface. Built-up edge occurs because the material easily adheres to the cutting edge, which ultimately changes the geometry of the tool and Ra increases [12]. Figure 5 a–e shows the eff ect of doc on various materials. It is observed that doc does not have a signifi cant eff ect on Ra. This may be due to the increase in strain volume with increasing doc. Thus, severe deformation of the workpiece results in more surface irregularities and hence poor surface quality. Zou et al. [25] also obtained similar results. Doc is less signifi cant for Ra than Vc and f [11]. At higher values of technological parameters, the thermal wear of the tool and surface roughness increase [3]. Comparison of cutting temperatures of SS 316, EN 8, SAE 8620 and Al 380 To obtain a comprehensive understanding of the infl uence of input parameters on cutting temperature, three-dimensional (3-D) surface plots are constructed by varying the process parameters for all cutting materials. These visual representations use empirically derived equations to ensure accuracy. Figure 6 shows three-dimensional diagrams illustrating the cutting temperature changes during turning of SS 316, EN 8, SAE 8620 and Al 380 stainless steels for PVD-coated (TiAlN) tools obtained using equations (V)–(VIII).
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