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Öğe Abrasive wear behaviour of cast Al-Si-Mn alloys(Sage Publications Ltd, 2019) Cetin, MelikIn this paper, the effect of manganese (wt%) and size of the Al2O3 abrasive grains of abrasive wear behaviours of Al-Si-(0.16-0.76%) Mn alloy was examined. Abrasive wear experiments were conducted against abrasive Al2O3 paper grains with diameters in the variety of 38-250 mu m, under the normal load range of 10, 20 and 30 N and the sliding velocity of 0.1 m s(-1). Wear measurements have shown that the wear rate of the material is dependent on the manganese content and the abrasive grain size. The best wear resistance is in the content of 0.73 Mn, which is associated with increased toughness and strength. The Al-Si casting alloy which had 0.73% Mn content exhibited lower wear rate than the Al-Si-0.16/0.22/0.23% Mn alloys after scoured on fine abrasive Al2O3 grains (<65 mu m). Wear experiments achieved on Al2O3 grains having sizes greater than 65 mu m revealed that, the cast Al-Si- alloy which had 0.73% Mn content had lower wear rate than the cast Al-Si-0.16/0.22/0.23% Mn alloys.Öğe Corrosion, Wear and Mechanical Properties of Boron Added Cast 304 Stainless Steel(Maik Nauka/Interperiodica/Springer, 2020) Cetin, Melik; Olmez, ErsinThe main objective of this research was to examine the effect adding B at 0, 100, 170 ppm had on the mechanical properties, wear and corrosion behaviour (in two different corrosive media) of cast 304 stainless steels. The microstructures, wear surface and corrosion morphologies were examined by optical microscopy, X-ray diffraction analyses and scanning electron microscopy (SEM). The cast 304 stainless steels with boron addition as 0, 100, 170 ppm, were used to investigate their corrosion behaviours by electrochemical potentiodynamic polarisation capacities in 5% HCl and 5% HNO(3)solutions at laboratory environment. Wear tests were conducted in a pin-on-disc type wear tester. Optimum properties in relations of improved strength and wear resistance without loss in hardness were obtained when the cast 304 stainless steel contained 100 ppm B. At B contents higher than 100 ppm decrease of the hardness was accompanied an increase in strength and wear resistance. It was found that wear loss cast 304 stainless steel with B addition decreased with the increase of sliding distance, when compared with 0 ppm B addition cast 304 stainless steel. With regard to results of the corrosion experiment,I(cor)tended to decrease the addition 110 ppm B in 5% HCl solution, leading to a rise in the corrosion resistance. Adding B to the cast 304 stainless steels helped to enhance its corrosion resistance, except that its intergranular corrosion resistance reduced, which can be seen by examining the corrosion morphology. The improved wear behaviour and corrosion resistance of cast 304 stainless steel was attributed to the adding boron cast 304 stainless steel.Öğe Effect of Boron Added Corrosion Behavior of Cast 304 Stainless Steel(Maik Nauka/Interperiodica/Springer, 2019) Cetin, MelikSeven groups of the cast 304 stainless steels with boron addition as 0, 10, 20, 30, 40, 50, and 60 ppm were used to investigate their corrosion behavior by electrochemical potentiodynamic polarisation capacities in 10% HNO3 solutions at laboratory environment. The effect of solution heat treatment at 800 degrees C, 900 degrees C and 1000 degrees C for 1h on corrosive resistance of cast 304 stainless steel was also investigated. Microstructures and corrosion morphologies were examined by optical microscopy, X-ray diffraction analyses and scanning electron microscopy. Because of experiments, improvement of corrosion resistances depending on the amount of added B and heat treatment conditions were observed. Adding B to the cast 304 stainless steels improved its resistance to corrosion, but its resistance to intergranular corrosion reduced, which can be seen by the corrosion morphology. The improved corrosion resistance of cast 304 stainless steel was attributed not only to the added boron, but also solution-annealing treatment compared with non-borided cast 304 stainless steel.Öğe Effect of thermal degradation on the properties and wear behavior of Cr-V-C composite coatings grown on ductile iron(Elsevier Science Sa, 2021) Gunen, Ali; Kanca, Erdogan; Karakas, Mustafa Serdar; Gok, Mustafa Sabri; Kalkandelen, Muge; Kurt, Bulent; Cetin, MelikThe thermal fatigue behavior of chromium vanadium carbide (Cr - V - C) coatings and the wear of the coatings after thermal fatigue cycling was studied. The Cr - V - C coatings were grown on the surface of a ductile iron using thermo-reactive diffusion (TRD) and subjected to thermal fatigue in the temperature range of 25 to 750 degrees C for up to 500 cycles. Characterizations were made using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, microhardness measurements and wear tests. The Cr - V - C coated samples displayed superior thermal fatigue and wear resistance compared to the untreated ductile iron, mainly due to the dissolution of graphite nodules in the vicinity of the surface during TRD. The dissolution of graphite reduced the possibility of failure initiating from graphite nodules and graphite-matrix interfaces. Increasing the number of cycles resulted in increased flaking and decreased wear resistance in both the Cr - V - C coatings as well as the untreated ductile iron. Although much of the Cr V C coating was lost (due to flaking) after thermal cycling, the absence of graphite near the surface still provided improved resistance to wear in the TRD-treated samples. The results of this study indicate that TRD coatings hold great promise for use in the industrial applications.Öğe An Experimental Study on Boron Carbide Reinforced Open Cell Aluminum Foams Produced via Infiltration Technique(Eos Assoc, 2018) Sunar, Talha; Cetin, MelikLight structures and parts are very effective for new engineering applications. Their considerably low densities, high energy absorption capabilities, and desirable mechanical properties make them useful for particularly automotive, defense and aerospace industries. Besides these positive properties, it is known that the production and processing of cellular materials is very tough and worth the effort. Recently, with advances in new technologies like 3D printing or selective laser melting, now different types of cellular materials can be produced. But manufacturing of metallic foams via casting especially replication or infiltration method is fairly an economic method when compared with other methods. In this study, vacuum-gas infiltration set-up was used to produce B4C reinforced aluminum foams. The mentioned method involves the addition of space holder materials and a dissolution technique to remove them after solidification of the metal. As space holder materials NaCl particles were selected and mixed with B4C powders to produce B4C reinforced A360 aluminum foam. By changing the weight ratio of B4C particles, the alteration of properties like porosity, compression strength, and energy absorption capacity was investigated. Additionally, computer tomography views were obtained to see and interpret the microstructures of the foams. Compression tests were carried out to evaluate the mechanical behavior of the foams under static loading. The porosities of samples obtained as between 65-75%. The compressive strength increased with rising relative density.Öğe Manufacturing of B4C particle reinforced A360 aluminium cellular composite materials by the integration of stir casting and space holder methods(Sage Publications Ltd, 2021) Sunar, Talha; Cetin, MelikStir casting method has become prominent for fabrication of metal matrix composites in recent years. This method can be adjusted for casting around space holding particles to obtain cellular composite materials. In this study, a specific method which is a combination of stir casting and space holder techniques were used to produce open-celled A360 aluminium-B4C composite foams with regular sized and distributed pores. Weight ratios of reinforcement particles determined as 0.5, 1, 1.5 and 2%. The influences of particle reinforcement on the microstructure and the mechanical behaviour of composite foams were investigated. Microstructures were analysed with optical microscope (OM), scanning electron microscope (SEM). Compression and hardness tests were carried out to observe the effects of reinforcement on mechanical properties. Compression strength properties and hardness of composites increased with the ceramic reinforcement, however the plastic strength of the composite foams showed worsening trend after a certain reinforcement ratio (0.5 wt.%). Energy absorption properties of the composite foams showed parallel trends with compressive strength properties.Öğe Microstructural characterization, boriding kinetics and tribo-wear behavior of borided Fe-based A286 superalloy(Elsevier Science Inc, 2022) Gunen, Ali; Keddam, Mourad; Alkan, Sabri; Erdogan, Azmi; Cetin, MelikIron-based superalloys are alloys produced for use in corrosive environments as an alternative to high-cost nickel-based superalloys. However, their average strength and hardness, attributed to their austenitic structures, limit their use in tribological applications. In an attempt to counter these drawbacks, boriding was applied to an iron-based A286 superalloy having an initial surface hardness of 320 HV. Boriding kinetics, some mechanical properties, and tribo-wear (ambient air and 3.5 NaCl environment) behaviors of the formed boride layers were investigated. Multicomponent boride layers (consist of FeB, Fe2B, CrB, NiB, Ni4B3) were formed on the surface of the alloy, with hardness and thickness values of 1498-1961 HV and 20-130 mu m, respectively, depending on the boriding temperature and the treatment time. The integral diffusion model was adopted to deal with the kinetics of monoboride and hemiboride layers formed on the surface. The boron activation energies of FeB, Fe2B, and DZ layer were estimated as equal to 175.86, 198.7, and 205.73 kJ mol- 1, respectively. As a result of increased surface hardness, all of the borided samples displayed reduced friction coefficients and higher wear resistance compared to the untreated alloy, in both ambient air and 3.5% NaCl. However, the increase in wear resistance was not proportional to the increase in hardness; while the best wear resistance was obtained in samples borided at 850-950 degrees C for 6 h, the lowest wear resistance was obtained in samples borided for 4-6 h at 1050 degrees C. This situation was caused by the Kirkendall effect and residual stresses in the structure of alloying elements with different diffusion rates due to the high-temperature effect of the boriding process.Öğe Microstructural, wear and corrosion characteristics of boronized AISI 904L superaustenitic stainless steel(Pergamon-Elsevier Science Ltd, 2021) Cetin, Melik; Gunen, Ali; Kalkandelen, Muge; Karakas, Mustafa SerdarAISI 900 series stainless steels are considered as low-cost alternatives to nickel-based superalloys used for highly corrosive environments. However, in terms of mechanical properties, they have average strength and hardness similar to other austenitic stainless steel grades and this often limits their use. If a 900 series alloy were to be used under tribocorrosive conditions, its surface properties would have to be improved by a wear and corrosion resistant coating. In this study, AISI 904L steel was pack boronized in a solid medium at temperatures of 900, 1000 and 1100 ?C for 2, 4 and 6 h with nano-sized boronizing powders. The grown boride layers were evaluated using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffractometry, 2D profilometry, microhardness measurements, ball-on-disk type wear tests and electrochemical corrosion tests. Characterization studies revealed a complex boride layer consisting of FeB, Fe2B, CrB, Cr3B4, Ni3B and Mo2B phases with 2366?2396 HV hardness. Wear tests showed that the abrasive wear resistance of the AISI 904L steel was improved by up to 40 times. The corrosion resistance of boronized AISI 904L was inferior to untreated AISI 904L in 3.5% NaCl, but comparable to AISI 316L.Öğe Pin-On-Disc Characterization of Brass/Ferritic and Pearlitic Ductile Iron Rubbing Pair(Walter De Gruyter & Co, 2011) Cetin, MelikWear behaviour of special brass produced through two different methods (centrifugal and sand casting) was investigated. The wear tests were carried out at sliding velocities of 0.2 ms(-1), 0.3 ms(-1), 0.4 ms(-1) and 0.5 ms(-1) and under 10 N, 20 N, and 40 N variable loads. The sliding distance was 600 m for all the tests. A pin-on-disc device with round specimen inserts was used to conduct friction and wear tests in which the friction coefficient, the contact temperature and the linear wear of the tribo-pairs were continuously recorded against sliding distance. Two different materials were used as the counterparts, namely ferritic ductile iron equivalent to GGG40 and pearlitic ductile iron equivalent to GGG60. The microstructures and wear scars of the brass specimens were examined by optical, scanning electron microscopy (SEM) and X-ray microanalyses by EDAX. A correlation between hardness and wear volume rate was established for the investigated centrifugally cast and sand cast brass specimens. The volume rate of specimens produced by sand casting method was generally found to be higher than those of centrifugally cast specimens. Ferritic ductile counterpart led to higher wear volume rate than pearlitic ductile counterpart for the both specimens. Severe abrasive wear scars were observed for the sand cast specimens/ferritic ductile iron pair. However, severe adhesive wear took place for the centrifugally cast specimen/pearlitic ductile iron pair.Öğe Residual stress measurement by strain gauge and X-ray diffraction method in different shaped rails(Pergamon-Elsevier Science Ltd, 2019) Turan, Muhammet Emre; Aydin, Fatih; Sun, Yavuz; Cetin, MelikIt is well known that rails are the most important part of railway infrastructure. Besides good wear and fatigue resistance, appropriate residual stress value in rails is required to improve performance of rails. The knowledge of residual stress types and distributions gives prediction the mechanical properties of materials for manufacturer. This study aims to make comparison between destructive and non-destructive residual stress measurement techniques and to investigate the influence of rail head geometry on residual stress by the use of two different quality rails. One of the rails is R260 grade and the other one is R260 grooved rail. In addition to residual stress measurement with strain gauge (cuffing) and X-ray diffraction method, microstructures of the specimens were examined. Results show that grooved rail has higher residual stress and different types of stress were observed for samples which are supported by X-ray and strain gauge method.Öğe Wire-EDM performance and surface integrity of Inconel 718 with unique microstructural features fabricated by laser powder bed fusion(Springer London Ltd, 2024) Gokcekaya, Ozkan; Gunen, Ali; Ceritbinmez, Ferhat; Bahador, Abdollah; Nakano, Takayoshi; Cetin, MelikInconel 718 alloy is difficult to machine using conventional methods due to its physical properties. Thereby, additive manufacturing (AM) of IN718 components with near-net shapes has been extensively studied. Even though AM processes provide shape and size accuracy, there is still the need for the machining of the AM-processed components to achieve the final shape of a component. Laser powder bed fusion (LPBF) has been successfully utilized to fabricate near-net shape IN718 components; moreover, the microstructure of LPBF-IN718 was unique owing to the AM processing, resulting in differences in grain size, grain boundary characteristics, and grain orientations. Furthermore, these microstructural characteristics are expected to alter the machining performance of IN718. Therefore, this study investigated the wire electro-discharge machining (WEDM) performance of LPBF-718 samples compared to wrought IN718 while focusing on the unique microstructure characteristics of LPBF-IN718 samples (lamella, single-crystal, ploy-crystal). Three different cutting strategies (rough, semi-finish, and finish) were implemented to understand the performance of the multi-pass cutting phenomenon and its effect on the surface of IN718. For all samples, rough (single pass) cutting displayed high roughness, while finish (three passes) cutting exhibited good surface quality. Compositional analyses on the machined surface showed debris formation including Zn and Cu-containing recast material, indicating wire erosion. The surface of single-crystal LPBF-IN718 after the WEDM process was smooth owing to its large grain size and less amount of grain boundary, resulting in slow cutting speed but a good surface finish. Thus, this study, for the first time, investigated the effect of unique microstructural characteristics of LPBF-fabricated IN718 on WEDM performance and machined surface quality.
