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    Examining the machinability of 38MnVS6 microalloyed steel, cooled in different mediums after hot forging with the coated carbide and ceramic tool
    (SAGE Publications Ltd, 2021) Özlü, Barış; Demir, Halil; Türkmen, Mustafa; Gürbüz, Süleyman
    In this study, the effect of the microstructure, hardness, and cutting speed on main cutting force and surface roughness in medium carbon microalloyed steel cooled in different mediums after hot forging, was investigated. As-received sample, which was not hot forged, and the samples cooled in the sand, air, oil, and polymerized water after hot forging were used for the experimental studies. The machinability tests were performed via turning method by using coated carbide and coated ceramic cutting tools with five cutting speed (120, 150, 180, 210, and 240?m/min), constant feed rate (0.04?mm/rev), and constant depth of cut (0.6?mm). The microstructure examinations of the samples were carried out and their hardness values were determined. Also, the wear of cutting tools were examined with scanning electron microscope. In the experimental study, it was revealed that the microstructure, hardness and cutting speed had a significant effect on the surface roughness values of the samples cooled in dissimilar environments following forging. Moreover, the samples cooled in air and polymerized water, whose hardness increased depending on the increase in the cooling rate, had the highest cutting force after machining by using the coated carbide and ceramic tool.
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    The effect of mechanical properties and the cutting parameters on machinability of AISI 5140 steel cooled at high cooling rates after hot forging
    (Gazi Üniversitesi, 2019) Özlü, Barış; Demir, Halil; Türkmen, Mustafa
    In this study, the effect of mechanical properties and cutting parameters (Cp) on the machinability of AISI 5140 steel cooled at high cooling rates after hot forging was investigated. The microstructural examinations and hardness measurements of the asreceived AISI 5140 steel and the workpieces cooled in the oil and polymerized water after hot forging were performed. Turning process was conducted by using a coated ceramic tool at five different cutting speeds (Vc) (120, 150, 180, 210, and 240 m/min), four different feed rates (fn) (0.04, 0.08, 0.12, and 0.16 mm/rev), and four different depths of cut (ap) (0.4, 0.6, 0.8, and 1 mm) under dry machining conditions. SEM examinations of the cutting tools were also performed. It was seen from the results that the changing microstructure and hardness values had a significant effect on cutting forces (Fc) and surface roughness (Ra) from the Cp depending on cooling rate. While the highest Fc were reached in the workpiece with the highest hardness cooled in the polymerized water after hot forging, the lowest surface roughness (Ra) was obtained in the same workpiece.
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    The Effect of Mn and Ti Ratio on Microstructure and Mechanical and Machinability Properties of 316 L Stainless Steel Used in Biomedical Applications
    (Multidisciplinary Digital Publishing Institute (MDPI), 2023) Türkmen, Mustafa; Tanouz, Alla Muhammed; Akgün, Mahir; Erden, Mehmet Akif
    In this study, titanium (Ti) and manganese (Mn) element powders in determined amounts (0.35–0.75 and 1.5 wt %) were added into the 316 L stainless steel matrix by means of powder metallurgy (PM) technology, either individually or in pairs, and the desired composition was obtained as a powder mixture. The powders used in the study were cold-pressed tensile sample molds prepared in ASTM E8M standards, unidirectionally cold-pressed under 750 MPa compression pressure and formed into blocks. After pressing, the raw strength samples were sintered in an atmosphere-controlled tube furnace at 1250 °C for two hours in an argon atmosphere. The microstructure and mechanical properties of the produced PM steels were characterized using an optical microscope, SEM, EDS, tensile test, and hardness test. The results showed that the stainless steel samples with 0.35 (Ti and Mn) added to 316 L stainless steel had the highest yield strength, tensile strengths, and hardness strengths. However, with the addition of 0.75–1.5 Ti, 0.75–1.5 Mn and 0.75–1.5 (Ti and Mn) to 316 L stainless steel, a decrease was observed in the mechanical properties. Moreover, the stainless steel sample with 0.35 (Ti and Mn) added to 316 L stainless steel is better than other samples in terms of surface quality.