Browsing by Author "Gençer G.M."

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    Surface nanocrystallization of SAE 1008 steel by single and multipass thread rolling process; [Nanokristallisierung der Oberfläche von SAE 1008 Stahl durch Ein- und Mehrfach-Gewindewalzen]
    (Wiley-VCH Verlag, 2017) Kahraman F.; Gençer G.M.; Kahraman A.D.
    In this study, the layers are investigated which are obtained on the surfaces of the single and multi-pass thread rolled screws. It is observed that deformation is more homogenous depending on the pass number and thread laps failure do not form on the 3-passed threads. A nanocrystallized layer that thicknesses and size depends on deformation amount is determined on the surfaces of the thread rolled SAE 1008 steel. While top of this layer has finer grain sizes, depending on the deformation amount grains coursed and oriented by the deformation direction. The finer grains are observed in the single pass thread rolled sample as size of 136 nm at the 15 μm inside from the surface of the root of the thread. Compared with bulk material, significant hardness increase is observed on the surfaces of the all thread rolled samples. The effect of pass number on the hardness is very low, increases of the pass number, hardness increases slightly. But thicknesses of layer are enhanced to increase the pass number. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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    Low-temperature nitriding behavior of compressive deformed AISI 316Ti austenitic stainless steels
    (World Scientific Publishing Co. Pte Ltd, 2019) Kahraman F.; Gençer G.M.; Kahraman A.D.; Yolcu C.; Kahraman H.
    The effects of compressive cold deformation under the quasi-static loads on the nitride formation, nitride layer growth and surface hardness properties were researched in this study. Martensite structure did not form in AISI 316Ti stainless steel as a result of quasi-static deformation. Diffusion layer did not form in all nitrided samples. Both the deformed and undeformed samples have only compound layer on the surfaces at the low-temperature nitriding conditions (400°C, 7h). According to the X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS) and electron probe microanalysis (EPMA) results, S-phase and chromium nitride (CrN) were formed in the compound layers of the deformed samples. However, CrN did not form in the compound layer of the undeformed sample. The optical microscope (OM) results showed that the compressive cold deformation increased the nitrogen diffusion rate and led to thicker nitrided layer than the undeformed sample under the same plasma-nitriding conditions. All nitrided layers presented higher microhardness values (∼1200HV) when compared with the untreated sample hardness. It was also verified that the deformation amount did not affect significantly the nitrided layer hardness. © 2019 World Scientific Publishing Company.