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    The Effect of Temperature on Wear Performance of High-Velocity Oxy-Fuel Sprayed WC-10Co-4Cr Coating on AA7075-T6 Substrate
    (Springer, 2022) Ceviz, Mehmet; Misirli, Cenk; Karabeyoglu, Sencer Sureyya
    In this study, the friction wear performance of a High-velocity oxy-fuel (HVOF) sprayed WC-10Co-4Cr coated AA7075-T6 substrate was investigated against a WC-4Co ball at different temperatures using a pin-on-disk tribometer. WC-10Co-4Cr coating was deposited with a commercial HVOF-K2 spray (GTV MF-HVOF-K 1000 compact), O-2 and kerosene as fuel gases with flow rates of 900 L/min and 26 L/h, respectively. Spraying was carried out with a rotation speed of 200 rpm, a particle feed rate of 1.8 rpm at a distance of 380 mm and a scanning distance of 5 mm. As HVOF spray, a commercial WC-10Co-4Cr powder (GTV 80.76.1.G) with a particle density of 4.63 g/cm(3) was utilized. The diffusion of coating to the substrate was investigated by scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDX). The hardness of the as-sprayed coating was measured using a micro Vickers hardness tester. The friction and wear tests were performed at a sliding speed of 100 mm/s for 1800 s under a fixed load of 3 N at 25, 100, 200 and 300 degrees C. The wear rate increased five times at 300 degrees C testing compared to room temperature (RT), but the average coefficient of friction (COF) value increased from 0.30 to 0.48 for 200 degrees C testing and then decreased to 0.36 for 300 degrees C. The powder and coating microstructures were analyzed using x-ray diffractometer (XRD) analysis. Morphological characterizations were accomplished by SEM and a wide field confocal microscope (WCM/profilometer), and wear mechanisms were examined. The wear mechanism was abrasive until 100 degrees C, but a temperature increase allowed for adhesive wear, plastic deformation and oxidation fatigue. Oxide layers and crack propagation took place in accordance with applied load and thermal expansion of the AA7075-T6 substrate. Oxide layers on the worn surface enabled the coefficient of friction to decrease after 200 degrees C. Oxide delamination and pile-ups were observed at 300 degrees C.
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    AN EXPERIMENTAL STUDY ON WALL THICKNESS DISTRIBUTION IN THERMOFORMING
    (Lublin Univ Technology, Poland, 2017) Karabeyoglu, Sencer Sureyya; Eksi, Olcay; Erdogan, Selcuk
    In this work, Polystyrene (PS) sheets were thermoformed in predetermined conditions. Wall thickness distributions obtained by experimental method in PS thermoformed products. Then the same thickness distributions were predicted by using Geometric Element Analysis (GEA). The thickness results were obtained experimentally, compared to thickness distributions which were predicted by GEA. It has been found that GEA does not precisely reveal thickness distributions.
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    An Investigation on Thermal Dry Sliding Wear Performance of Wrought AA 7075-T6
    (Springer India, 2022) Ceviz, Mehmet; Misirli, Cenk; Karabeyoglu, Sencer Sureyya
    The thermal frictional behavior of AA 7075-T6 against a WC-6Co ball for different temperatures was investigated to characterize the worn surface in terms of wear rate, coefficient of friction (COF) and hardness using a high temperature pin-on-disk tribometer. Microstructural composition was depicted after etching to show the precipitates. The hardness of the sample tested at room temperature (RT) was measured as HV 158.0, which dropped by similar to 56% in the 300 degrees C test. The wear rate and COF values increased over 10X in accordance with test temperature. The temperature increase loosened the structure, and the wear rate was negatively affected. A detailed tribological characterization was carried out using SEM and EDX, and wear track profiles were observed by cutting the samples with EDM and then comparing with the cross-sectional profile images (WCM). At RT and 100 degrees C, a partial abrasive wear mechanism was present; however, the temperature increase improved plastic deformation and adhesive wear. Oxide layer formation allowed oxidation cracks, and temperature increase proportionally improved wear rate. Possible phases were investigated using XRD to show the heat treatment effect of test temperatures.