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Öğe Dry sliding wear behaviours of filled welded train rail(Natl Acad Sciences Ukraine, Inst Metal Physics, 2007) Boz, M.The purpose of this work is to investigate sliding wear behaviour of the wearing train rail welded by the electric-arc welding technique. Samples are obtained from the wearing rail filled by the welding, using a various kind of manual arc-welding metal electrodes. The weld metal is characterized according to filling electrodes in terms of both hardness and microstructure. Wear behaviour of the filling weld metal is investigated in conditions of various loadings and distances. In addition, the friction coefficient of samples is determined according to the applied loadings and wear distances. Experimental results show. that the increase in loading and wear distance exerts the great influence on wear-resistance performances of samples. The samples having higher hardness demonstrate high wear-resistance performances. Also, a metallographic investigation indicates that the samples having the small-size grains display the better wear resistance than the samples containing the larger-size grains.Öğe Dry sliding wear behaviours of filled welded train rail(2007) Boz, M.The purpose of this work is to investigate sliding wear behaviour of the wearing train rail welded by the electric-arc welding technique. Samples are obtained from the wearing rail filled by the welding, using a various kind of manual arc-welding metal electrodes. The weld metal is characterized according to filling electrodes in terms of both hardness and microstructure. Wear behaviour of the filling weld metal is investigated in conditions of various loadings and distances. In addition, the friction coefficient of samples is determined according to the applied loadings and wear distances. Experimental results show that the increase in loading and wear distance exerts the great influence on wear-resistance performances of samples. The samples having higher hardness demonstrate high wear-resistance performances. Also, a metallographic investigation indicates that the samples having the small-size grains display the better wear resistance than the samples containing the larger-size grains.Öğe Effect of different amounts of graphite on the sintering and transverse rupture properties of powder metal parts(2006) Boz, M.; Kurt, A.Iron powders were mixed with graphite powders by 1-15 wt pct to produce block samples using powder metallurgy technique. The powders were blended in a three dimensional blender for 20 min and compacted in a die under 500 MPa by using an one directional press. Sinterability and mechanical properties of the samples with different carbon content were investigated. Sintering process was carried out on a belt furnace with flame curtain in dissociated ammonia atmosphere. Block samples produced were suitable for ASTM B-312 transverse rupture strength test apparatus and were tested with 0.050 kN/s velocity in a press under 100 g load. It was found that graphite amount up to 2 wt pct increased the contact area of particles and acted as a lubricant to affect the sintering behavior positively. The results indicated that the samples containing up to 5 wt pct showed good sintering behavior and also good hardness due to an increase in pearlite amount. However, the samples containing higher amount of graphite (more than 5 wt pct) affected the sintering behavior negatively due to the settlement of free graphite around the iron powders, which resulted in a decrease in the hardness and transverse rupture strength.Öğe THE EFFECT OF GAS PRESSURE ON POWDER SIZE AND MORPHOLOGY IN THE PRODUCTION OF AZ91 POWDER BY GAS ATOMIZATION METHOD(Polska Akad Nauk, Polish Acad Sciences, Inst Metall & Mater Sci Pas, 2018) Akkas, M.; Cetin, T.; Boz, M.In this study, the effect of gas pressure on the shape and size of the AZ91 alloy powder produced by using the gas atomization method was investigated experimentally. Experiments were carried out at 820 degrees C constant temperature in 2-mm nozzle diameter and by applying 4 different gas pressures (0.5, 1.5, 2.5 and 3.5 MPa). Argon gas was used to atomize the melt. Scanning electron microscope (SEM) to determine the shape of produced AZ91 powders, XRD, XRF and SEM-EDX analysis to determine the phases forming in the internal structures of the produced powders and the percentages of these phases and a laser measuring device for powder size analysis were used. Hardness tests were carried out to determine the mechanical properties of the produced powders. The general appearances of AZ91 alloy powders produced had general appearances of ligament, acicular, droplet, flake and spherical shape, but depending on the increase in gas pressure, the shape of the powders is seen to change mostly towards flake and spherical. It is determined that the finest powder was obtained at 820 degrees C with 2 mm nozzle diameter at 3.5 MPa gas pressure and the powders had complex shapes in general.Öğe The Effect of SiO2 on the Friction Performance of Automotive Brake Friction Materials(Natl Acad Sciences Ukraine, Inst Metal Physics, 2011) Boz, M.; Kurt, A.In this study, 0.5%, 1.0%, 2.0% and 4.0% weighted SiO2 powders were added to bronze-based materials, which are used as friction materials. Blended powders were mixed in three-dimensional mixers to provide a homogeneous mixture. Powders were pressed under pressure of 350 MPa using a single-action press. Pressed samples were sintered at 820 degrees C, for 20 minutes, in ammonia atmosphere. Sintered samples are tested in a wear test device. Wear and friction coefficient tests are carried out on sintered samples. As revealed, with higher amounts of SiO2, the friction coefficient is increased, and the wear ratio is decreased.Öğe The effect of SiO2 on the friction performance of automotive brake friction materials(2011) Boz, M.; Kurt, A.In this study, 0.5%, 1.0%, 2.0% and 4.0% weighted SiO2 powders were added to bronze-based materials, which are used as friction materials. Blended powders were mixed in three-dimensional mixers to provide a homogeneous mixture. Powders were pressed under pressure of 350 MPa using a single-action press. Pressed samples were sintered at 820°C for 20 minutes, in ammonia atmosphere. Sintered samples are tested in a wear test device. Wear and friction coefficient tests are carried out on sintered samples. As revealed, with higher amounts of SiO2, the friction coefficient is increased, and the wear ratio is decreased.Öğe Effect of welding speed to joinability on the friction stir welding(2004) Kurt, A.; Boz, M.; Özdemir, M.Although friction stir welding method has been developed for 10 years ago it has found intensive usage in industry now. In this study aluminium sheets with the size of 5×50×120 mm were joined by friction stir welding method by using a milling machine. Joining processes were carried out at 6.25, 10, 16 and 20 mm/min welding speeds and 800 spindle speed. In order to investigate the effect of welding speeds on metallurgical and mechanical properties, metallographic and mechanical tests were carried out on the welded areas of the samples.Öğe INVESTIGATION OF GAS PRESSURE EFFECT ON POWDER CHARACTERIZATION OF AZ31 ALLOY PRODUCED BY GAS ATOMIZATION METHOD(Yildiz Technical University, 2019) Akkas, M.; Em, Kara, K.M.; Cetin, T.; Boz, M.In this study, the effect of gas pressure on the shape and size of the AZ31 alloy powder produced by using the gas atomization method was investigated experimentally. Experiments were carried out at 840°C constant temperature, in 2 mm constant nozzle diameter and by applying 4 different gas pressures (5, 15, 25 and 35 bar). Argon gas was used to atomize the melt. Scanning electron microscope (SEM) to determine the shape of produced AZ31 powders, XRD and XRF analysis to determine the phases forming in the internal structures of the produced powders and the percentages of these phases and a laser measuring device for powder size analysis were used. The general appearances of AZ31 alloy powders produced had general appearances of complex, ligament, acicular, droplet, flake and spherical shape, but depending on the increase in gas pressure, the shape of the powders is seen to change mostly towards droplet and spherical. © 2019 Yildiz Technical University. All Rights Reserved.Öğe The Production of AZ31 Alloys by Gas Atomization Method and Its Characteristics(Pleiades Publishing Inc, 2020) Em Akra, K. M.; Akkas, M.; Boz, M.; Seabra, E.The aim of this study is to investigate the AZ31 alloy powder production and characterization processes experimentally using the gas atomization method. For this purpose, firstly, the design and production of gas atomization units were done at Karabuk University Faculty of Technology Department of Manufacturing Engineering. In this gas atomization unit, the manufacturability of AZ31 powder from magnesium alloys was investigated by the gas atomization method which is one of the production methods by powder metallurgy. The parameters and the literature used in the production of materials similar to the AZ31 alloy are taken into account as producibility parameters. In the gas atomization method, parameters such as nozzle diameter, gas pressure, and temperature must be controlled in order to produce the desired properties in metal powder production. The diameter of the nozzle is crucial because it affects the gas pressure and temperature, the size of the powder, and the shape of the powders. Experimental studies were carried out using 3 different temperatures (790, 820, and 850 degrees C), 4 different nozzle diameters (2, 3, 4, and 5 mm) and 4 different gas pressures (5, 15, 25, and 35 bar). In the molten metal atomization process and in the process of forming a protective gas atmosphere, argon gas was preferred. Scanning electron microscopy (SEM) was used to determine the shape of the AZ31 powders produced, XRD, XRF, and SEM-EDX analyses were used to determine the phases in the internals of the produced powders and percentages of these phases. Laser measurement devices were used for powder size analysis and hardness tests were performed to determine the mechanical properties of the produced powders. The powders produced were pressed into masses at 4 different pressing pressures (300, 400, 500, and 600 MPa). The best sinterability values of the bulked powders and sintering process were performed at 3 different temperatures (500, 550, and 600 degrees C). Density measurements were made after pressing and sintering the powders. As a result of the experimental studies, it was found that the powder size decreased with the increase of the gas pressure but the nozzle diameter, and the powder shape changed to the dripping and the spherical in the ligament and complex form. It has been observed that the temperature has no significant effect on the powder size and shape.Öğe Wear properties of the bronze brake lining produced with powder metallurgy(1999) Boz, M.; Kurt, V.A.Wear properties of the bronze brake lining produced with powder metallurgy (P/M) method were compared to asbestos based brake lining. Bronze powder was pressed under different pressure and sintered at 810 C in ammoniac gas atmosphere for 75 minutes. The wear properties of the sintered specimens were compared to the asbestos based brake lining by using wear tests. It is determined that temperature increase in bronze specimens was lower than that in asbestos based lining but wear ratio in bronze specimens was higher.
