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    Evaluation of the mechanical properties and machinability of chromium and molybdenum-added powder metallurgy steels
    (SAGE Publications Ltd, 2024) Vassouf, Abdul Rahman; Akgün, Mahir; Erden, Mehmet Akif
    The present study focuses on the microstructure, mechanical properties, and machining aspects of powder metallurgy (PM) steel containing different rates of chromium (Cr) and molybdenum (Mo). PM steel alloys were pressed at 700?MPa and sintered at 1400°C in a mixture of nitrogen and hydrogen atmosphere for 1 hour. While the precipitates and fracture surfaces of the samples obtained were examined by scanning electron microscope (SEM) and EDS analyzes, the grain size and phase distributions were also examined with an optical microscope. Moreover, tensile and hardness measurement tests were carried out to determine the mechanical properties of the samples with different ratios of Cr and Mo content. The milling experiments were also performed without using coolant in a CNC milling machine at different cutting parameters. The surface roughness (Ra), tool wear (Vb), and wear mechanism were investigated under these conditions. The outcomes of this study reveal that the yield and tensile strength values of the samples with the addition of Cr and Mo increased but the elongation value decreased. The results also stated that the most effective process parameter for both Vb and Ra was the workpiece material and the regression models developed to estimate the output parameters (Vb and Ra) give successful results with high determination coefficients (R2) of 98.05% and 98.11%, respectively.
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    Influence of Ti and Nb addition on the microstructure, mechanical, and machinability properties of 316L stainless steel fabricated by powder metallurgy
    (Walter de Gruyter GmbH, 2023) Erden, Mehmet Akif; Uzun, Fatma Gül; Akgün, Mahir; Gökçe, Hasan
    In this study, titanium and niobium element powders in determined amounts (0.25 and 0.5wt%) were added into the 316L stainless steel matrix by means of powder metallurgy (PM) technology, either singly 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 8M standards, unidirectionally cold pressed under 700MPa compression pressure and formed into blocks. After pressing, the raw strength samples were sintered in an atmosphere-controlled tube furnace at 1325°C for 2h in an argon atmosphere. The microstructure and mechanical properties of the produced PM steels were characterized by optical microscope, SEM, EDS, and tensile test. The results showed that the stainless-steel samples with 0.25(Ti-Nb) added composition to 316L stainless steel had the highest yield strength and tensile strengths. However, with the addition of 0.5Ti, 0.5Nb, and 0.5(Ti-Nb) to 316L stainless steel, a decrease was observed in the mechanical properties. Moreover, the MQL machining is better on the machining output such as surface roughness and cutting temperature than dry machining in terms of a sustainable machining process.
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    Öğe
    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.