Yazar "Özbek, Onur" seçeneğine göre listele
Listeleniyor 1 - 15 / 15
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe AISI 304 ve AISI 316 Östenitik Paslanmaz Çeliklerin İşlenebilirliğinin Değerlendirilmesi(2017) Özbek, Nursel Altan; Çiçek, Adem; Gülesin, Mahmut; Özbek, OnurBu çalışmada AISI 304 ve AISI 316 östenitik paslanmaz çeliklerin işlenebilirliğini değerlendirmek amacıyla kaplamasız tungsten karbür kesici takımlar kullanılarak tornalama deneyleri yapılmıştır. Deneyler, kuru kesme şartlarında sabit kesme derinliği (2,4 mm), dört kesme hızı (100, 120, 140 ve 160 m/dak) ve üç ilerleme hızında (0,15, 0,3 ve 0,45 mm/dev) gerçekleştirilmiştir. AISI 304 ve AISI 316 çeliklerin işlenebilirliği takım aşınması, esas kesme kuvveti ve yüzey pürüzlülüğü açısından değerlendirilmiştir. Deney sonuçları AISI 316 çeliğinin işlenmesinde kesici takımın daha fazla aşındığını göstermiştir. Ayrıca AISI 316 çeliğinde daha yüksek kesme kuvveti ve yüzey pürüzlülüğü değerleri ölçülmüştür. Deneysel çalışma sonunda, AISI 316 çeliğinin AISI 304 çeliğine kıyasla işlenebilirliğinin zor olduğu ortaya konulmuşturÖğe AISI 304 ve AISI 316 Östenitik Paslanmaz Çeliklerin İşlenebilirliğinin Değerlendirilmesi(Gazi Univ, 2017) Özbek, Nursel Altan; Çiçek, Adem; Gülesin, Mahmut; Özbek, OnurIn this study, turning tests were performed to assess machinability of AISI 304 and AISI 316 austenitic stainless steels using uncoated tungsten carbide tools. The tests were conducted at four cutting speeds (100, 120, 140 and 160 m/min), three feed rates (0.15, 0.3 and 0.45 mm/rev), and a fixed depth of cut (2.4 mm) under dry cutting conditions. Machinability of AISI 304 and AISI 316 steels was evaluated in terms of tool wear, main cutting force and surface roughness. Experimental results showed that larger wear damages formed on the cutting inserts used for machining of AISI 316 steel. In addition, higher values of cutting forces and surface roughness were measured in machining of AISI 316 steel. In consequence of experimental study, it was found that AISI 316 steel had harder machinability characteristics than AISI 304 steel.Öğe Application of Deep Cryogenic Treatment to Uncoated Tungsten Carbide Inserts in the Turning of AISI 304 Stainless Steel(Springer, 2016) Özbek, Nurse Altan; Çiçek, Adem; Gülesin, Mahmut; Özbek, OnurThis study investigated the effects of deep cryogenic treatment (DCT) on the wear performance of uncoated tungsten carbide inserts. AISI 304 austenitic stainless steel, widely used in industry, was selected as the workpiece material. Cutting experiments showed that the amount of wear significantly increased with increasing cutting speed. In addition, it was found that DCT contributed to the wear resistance of the turning inserts. The treated turning inserts were less worn by 48 and 38 pct in terms of crater wear and notch wear, respectively, whereas they exhibited up to 18 pct superior wear performance in terms of flank wear. This was attributed to the precipitation of new and finer eta-carbides and their homogeneous distribution in the microstructure of the tungsten carbide material after deep cryogenic treatment. Analyses via image processing, hardness measurements, and SEM observations confirmed these findings.Öğe Effect of cryogenic treatment holding time on mechanical and microstructural properties of Sverker 21 steel(Walter De Gruyter Gmbh, 2022) Özbek, Nursel Altan; Özbek, OnurThis study investigated the effects of shallow and deep cryogenic treatment on the microstructural and mechanical properties of Sverker 21 tool steel. After conventional heat treatment, shallow cryogenic treatment at -80 C for 2, 12, and 24 h and deep cryogenic treatment at -180 C for 2, 18, and 36 h were applied on the steel samples. After that, the samples were tempered at 200 C for 2 h. As a result of these treatments, the steel samples' hardness, toughness, and wear rate changes were determined, and their microstructural properties were investigated. As a result of the study, it was observed that the cryogenic treatment had positive effects on the mechanical and microstructural properties of Sverker 21 steel. Mechanical properties also improved with increasing holding time for both cryogenic treatment types. It has been found that the deep cryogenic treatment provides better mechanical properties compared to the shallow cryogenic treatment. The maximum hardness and wear resistance were obtained in the deep cryogenically treated sample for 36 h. Compared to the CHT sample, the hardness and impact energy of the DCT(36) sample increased by approximately 11.75% and 17.36%. An improvement of approximately 64% was observed in the wear rate.Öğe Effect of cryogenic treatment on wear behavior of Sleipner cold work tool steel(Elsevier Ltd, 2023) Kara, Fuat; Küçük, Yılmaz; Özbek, Onur; Özbek, Nursel Altan; Gök, Mustafa Sabri; Altaş, Emre; Uygur, İlyasCryogenic treatment, also known as subzero heat treatment, is a cooling process that complements conventional heat treatment to improve the properties of metals. Unlike coatings, it is a one-time, inexpensive, permanent operation that affects the entire part. This method is mainly applied to tool steels used in mold making. In this study, the changes caused by the effects of shallow and deep cryogenic treatment on Sleipner cold work tool steel were investigated in terms of microhardness, microstructure, coefficient of friction (COF), and wear rate (WR). For this purpose, the test specimens were subjected to the cryogenic treatments performed at two different temperatures (?80 ºC for the shallow cryogenic treatment (SCT) and ? 180 ºC for the deep cryogenic treatment (DCT)) and various retention times (12 h, 24 h for SCT and 12 h, 24 h, 36 h for DCT). Dry sliding wear tests were carried out under different loads (10 N and 20 N) and varying test durations (60, 120, and 240 min) at a constant sliding speed of 0.075 m/s. According to the microhardness results, it was determined that the cryogenic treatment increased the hardness by 6.53 %. According to the microstructure investigations, a more homogeneous structure was observed with the cryogenic treatment, and secondary carbide precipitations were detected. It was observed that the conventional heat-treated (CHT) sample gave the highest COF value with an average coefficient of friction of 0.63. The lowest COF value of 0.58 was observed in the DCT-12 sample. After the wear tests, the lowest wear rate value for both load values was obtained from the DCT-36 specimen. © 2023 Elsevier LtdÖğe Effect of cutting conditions on wear performance of cryogenically treated tungsten carbide inserts in dry turning of stainless steel(Elsevier Sci Ltd, 2016) Özbek, Nurse Altan; Çiçek, Adem; Gülesin, Mahmut; Özbek, OnurIn this study, the effects of cryogenic treatment on tool wear of uncoated tungsten carbide inserts were investigated in the turning of AISI 316 stainless steel. It was found that notch wear appeared at low and medium cutting speeds, while flank wear and crater wear formed at all combinations of the process parameters selected for turning. In addition, treated inserts exhibited superior wear performance to untreated ones. This can be attributed to high wear resistance and low thermal conductivity of treated inserts. The results were verified by analyses of microstructure and hardness, image processing and Xray diffraction. (C) 2015 Elsevier Ltd. All rights reserved.Öğe Effect of Eco-Friendly Minimum Quantity Lubrication in Hard Machining of Vanadis 10: A High Strength Steel(Wiley-V C H Verlag Gmbh, 2022) Altan Özbek, Nursel; Özbek, Onur; Kara, Fuat; Saruhan, HamitVanadis 10 SuperClean is a high vanadium alloyed powder metallurgy tool steel offering a unique combination of an excellent abrasive wear resistance in combination with a good chipping resistance. In this study, the effects of the eco-friendly (100% biodegradable plant-based) Minimum Quantity Lubrication (MQL) system on the cutting temperature, cutting tool vibration amplitude, tool wear, average surface roughness, and tool life in the turning of Vanadis 10 steel (50 HRC) used in the automotive industry are investigated. In the experiments, TiCN/Al2O3/TiN-coated cemented carbide tools are used. Experimental results showed that, compared to Dry machining, MQL produced remarkable improvements in terms of cutting temperature, cutting tool vibration amplitude, tool wear, and surface roughness. In addition, the Taguchi experimental design, ANOVA, and linear and quadratic regression analyses are applied to the experimental data. The statistical analysis found the most effective parameter on average surface roughness to be the cutting environment (86.31%). It is determined that the cutting speed was the most effective on vibration amplitude and tool wear (46.22% and 32.41%). The correlation coefficients for the linear and quadratic regression analysis were 0.9 and 0.95, respectively.Öğe The effect of vibration and cutting zonetemperature on surface roughness and tool wear ineco-friendly MQL turning of AISI D2(Elsevier Editora Ltda, 2020) Özbek, Onur; Saruhan, HamitToday, developments in technology have gained momentum more than ever, and the need for efficiency in production as well as in the ecological domain has increased significantly. Studies examining dry machining and coolant removal have been superseded by those presenting new cooling and lubrication techniques. The effects on surface roughness directly related to final product quality are being investigated in terms of tool life and employee health. This has resulted in more frequent use of the eco-friendly minimum quantity lubrication (MQL) technique, which has now become a major competitor to dry and coolant machining. In this study, AISI D2 cold work tool steel, a material widely used in the mold industry, was used as the workpiece. Tests were carried out under dry and MQL conditions and the temperature, cutting tool vibration amplitude, tool wear, surface roughness and tool life were evaluated. The experiments were carried out using two different cutting tool coating types (CVD-chemical vapor deposition and PVD-physical vapor deposition) and three different cutting speeds (60, 90 and 120 m/min) at a constant cutting depth (1 mm) and feed rate (0.09 mm/rev). Results revealed that tool wear, cutting temperature and cutting tool vibration amplitude were lower by 23, 25, and 45%, respectively, compared to dry cutting. Because of these improvements, the surface roughness of the workpiece was improved by 89% and tool life was increased by up to 267%. © 2020 The Authors.Öğe Effects of deep cryogenic treatment with different holding times on the mechanical properties of Al 7050-T7451 alloy friction stir welding(Walter De Gruyter Gmbh, 2023) Özbek, OnurThis study aimed to improve mechanical properties, which decreased in the weld area, with deep cryogenic treatment at different holding times. In the study, firstly, the formation of heat damaging the welding area was observed. The temperatures in the welding zone were measured on the shoulder with a thermal camera, on the material surface, and inside the material with a thermocouple. The effects of these temperatures during welding on the surface topography and mechanical properties were investigated. The effect of tempering heat treatment after deep cryogenic treatment applied for 6, 12, 18, and 24 h was investigated. It has been observed that tempering after cryogenic treatment applied to 7xxx series aluminum alloys reduces the hardness of the nugget zone but increases the hardness in the heat unaffected zone. In addition, it was observed that deep cryogenic treatment applied at different holding times positively affected the hardness, tensile strength, and % elongation in the weld area.Öğe Investigation of the Effect of Deep Cryogenic Process on Residual Stress and Residual Austenite(2021) Kara, Fuat; Uygur, İlyas; Özbek, Onur; Özbek, Nursel AltanThe cryogenic treatment, known as holding materials at sub-zero temperatures, is a method usedto improve the properties of metal and non-metallic materials in recent years. This method ismainly applied to tool steels used in mold making. In our country, the use of cryogenic processescontinues to be widespread by many private sector organizations, primarily in mold materials.The benefits of this process have been recognized in many sectors, from the defense industry tothe automotive industry. In this study, the macro hardness, micro hardness and microstructureproperties of Sleipner cold work tool steel, which was applied traditional heat treatment and deepcryogenic process for 24 hours, were examined and the changes in the mechanical properties andmicrostructure of the material were determined. However, by measuring the residual stress andresidual austenite amounts in the materials with the X-Ray Diffraction (XRD) Method, thedifference between the samples was determined. The macro hardness of the CHT and DCT-24samples was measured as 60.96 HRC and 61.46 HRC, respectively. Micro hardness values were also measured as 734.26 HV and 761.83 HV, respectively. Deep cryogenic treatment increasedmacro and microhardness by 0.5 HRC and 27.57 HV, respectively. The amount of residualaustenite decreased by 36% after deep cryogenic treatment. Axial and circumferential residualstress values also decreased by 48.84% and 36.52%, respectively. As a result, deep cryogenictreatment increased the hardness of Sleipner cold work tool steel, homogenized themicrostructure, reduced residual austenite and residual stress values and provided positiveimprovements.Öğe Investigation of the effects of cryogenic treatment applied at different holding times to cemented carbide inserts on tool wear(Elsevier Sci Ltd, 2014) Özbek, Nurse Altan; Çiçek, Adem; Gülesin, Mahmut; Özbek, OnurCutting tool costs is one of the most important components of machining costs. For this reason, tool life should be improved using some methods such as cutting fluid, optimal cutting parameters, hard coatings and heat treatment. Recently, another one of the methods commonly used to improve tool life is cryogenic treatment. This study was designed to evaluate the effects of different holding times of deep cryogenic treatment on tool wear in turning of AISI 316 austenitic stainless steel. The cemented carbide inserts were cryogenically treated at -145 degrees C for 12, 24, 36, 48 and 60 h. Wear tests were conducted at four cutting speeds (100, 120, 140 and 160 m/min), a feed rate of 0.3 mm/rev and a 2.4 mm depth of cut under dry cutting conditions. The wear test results showed that flank wear and crater wear were present in all combinations of the cutting parameters. However, notch wear appeared only at lower cutting speeds (100 and 120 m/min). In general, the best wear resistance was obtained with cutting inserts cryogenically treated for 24 h. This case was attributed to the increased hardness and improved microstructure of cemented carbide inserts. These improvements were confirmed through hardness, image processing, and XRD analyses. (C) 2014 Elsevier Ltd. All rights reserved.Öğe Investigation of The Effects of Shallow Cryogenic Treatment on The Mechanical and Microstructural Properties of 1.2436 Tool Steel(2022) Özbek, Onur; Özbek, Nursel AltanThis study investigates the effects of shallow cryogenic treatment on the microstructure, hardness and wear resistance of 1.2436 steel. For this purpose, quenched (QT) 1.2436 steel samples were subjected to shallow cryogenic treatment at -80 °C for 12 hours (SCT12) and 18 hours (SCT18). Hardness measurement and wear test were carried out on the samples and the samples were examined microstructurally. As a result of the study, it was observed that the cryogenic treatment provided a denser and homogeneous carbide distribution in the microstructure of 1.2436 steel. The amount of carbide in the microstructure increased by 18.80% with shallow cryogenic treatment for 18 hours. As a result of the hardness and wear tests, it was determined that the cryogenic treatment positively affected the hardness and wear resistance of 1.2436 steel. Compared to the quenched sample alone, the sample cryogenically treated for 18 hours exhibited 9.28% higher hardness and 34.37% less wear.Öğe Kriyojenik İşlemin Sürtünme Karıştırma Kaynağı Üzerine Etkilerinin Araştırılması(2022) Özbek, Onurİçeriğindeki elementler ve uygulanan yaşlandırmalar sonrası yüksek mekanik özelliklere sahip7xxx serisi alüminyum alaşımları, düşük özgül ağırlığa ve yüksek özgül mukavemete sahiptirler. Ayrıca uygulanan ısıl işlemler ile mükemmel korozyon dirençlerine sahiptirler. Bu sebeplerden ötürü enerji sarfiyatının çok önemli olduğu otomotiv, havacılık ve uzay sanayisinde sıklıkla tercih edilmektedirler. Ancak erime noktası düşük olan bu alaşımların kaynaklanması oldukça güç olduğundan sürtünme karıştırma kaynağı önemli bir alternatif sunmaktadır. Fakat kaynaklanan noktalardaki mekanik özellikler sürtünme karıştırma kaynağında da diğer yöntemlere kıyasla az da olsa düşmektedir. Sorunun çözümü için bu çalışmada sürtünme karıştırma kaynağı ile birleştirilen parçalara -180°C’de derin ve -80°C’de sığ kriyojenik işlem uygulanmıştır. Sürtünme karıştırma kaynağı sonrası gerçekleştirilen kriyojenik işlem kaynak bölgesi sertliği ve mikroyapısında önemli değişikliklere neden olmuştur. Özellikle derin kriyojenik işlem sonrası parçaların birleşme bölgelerinde gözlemlenen sertlik artışı oldukça önemlidir.Öğe Sığ Kriyojenik İşlemin Sleipner Soğuk İş Takım Çeliğinin Metalurjik Özellikleri Üzerindeki Etkisinin Araştırılması(2021) El, Enes; Kara, Fuat; Özbek, OnurSıfırın altındaki sıcaklıklarda malzemelerin bekletilmesi olarak bilinen kriyojenik işlem, son yıllarda metal ve metal olmayan malzemelerin mekanik özelliklerini iyileştirmek için uygulanan bir yöntemdir. Bu çalışmada, Sleipner soğuk iş takım çeliği üzerinde sığ kriyojenik işlemin etkilerinin neden olduğu değişimler makro sertlik, mikro sertlik, mikroyapı ve kalıntı östenit hacim oranı yönünden araştırılmıştır. Bu amaçla deney numuneleri önce geleneksel ısıl işlem ile sertleştirilerek 60-62 HRC değerine getirilmiş ardından -80 °C sıcaklıkta 18 saat süreyle sığ kriyojenik işlem uygulanarak, 200 °C’de 2 saat boyunca temperleme yapılmıştır. Kalıntı östenit ölçüm sonuçlarına göre östenit hacim oranında yaklaşık % 61 oranında azalma tespit edilmiştir. Sertlik sonuçlarına göre sığ kriyojenik işlem görmüş numunede makro sertlikte % 2 ve mikro sertlikte % 7’lik bir artış görülmüştür. Mikroyapı incelemelerine göre kriyojenik işlem ile daha homojen bir yapı gözlemlenmiş ve ikincil karbür çökelmeleri görülmüştür.Öğe Tornalamada kriyojenik soğutma ve minimum miktarda yağlamanın kesici takım aşınması ve titreşimine etkilerinin araştırılması(Düzce Üniversitesi, 2020) Özbek, Onur; Saruhan, Hamitİnsanoğlunun ihtiyaçlarını karşılayabilmek için teknoloji gelişiminin hiç olmadığı kadar ivme kazandığı günümüzde hem üretim verimliliği hem de ekolojik verimliliğe duyulan ihtiyacın belirgin şekilde arttığı görülmektedir. Bu nedenle sürdürülebilir imalat kapsamında içinde bulunduğumuz yüzyılda teknolojinin gelişimiyle birlikte yeni soğutma ve yağlama çalışmaları giderek önem kazanmıştır. Bu çalışmada, sürdürülebilir imalat için en basit yöntem sayılabilecek kuru tornalama ile minimum miktarda yağlama, kriyojenik soğutma ve bu iki yöntemin birlikte kullanıldığı karma bir yöntem deneysel olarak karşılaştırılmıştır. Deneyler CVD (Chemical Vapour Deposition - Kimyasal Buhar Biriktirme) ve PVD (Physical Vapour Deposition - Fiziksel Buhar Çökeltme) yöntemleri ile kaplanmış tungsten karbür takımlar kullanılarak 60, 90, 120 m/dak kesme hızlarında; 0,06, 0,09, 0,12 mm/dev ilerleme hızlarında ve 1 mm sabit kesme derinliğinde gerçekleştirilmiştir. Tüm kesme şartları için toplamda 72 adet deney gerçekleştirilmiş ve bu deneylerin tümünde yüzey pürüzlülüğü için Ra, Rz değerleri, kesme bölgesi sıcaklığı, üç eksende kesici takım titreşimi ve kesici takım aşınması değerleri ölçülmüştür. Ayrıca farklı soğutma yağlama türlerinin kesici takım ömrüne etkisinin belirlenebilmesi için bir dizi deney gerçekleştirilmiştir. Deney sonuçları MQL (Minimum Quantity Lubrication - Minimum Miktarda Yağlama) tekniğinin yüzey pürüzlülüğünde kuru tornalamaya göre %90,12 daha iyi, MQL+Kry (Minimum miktarda yağlama+Kriyojenik soğutma) yönteminin kesme bölgesi sıcaklığı açısından kuru tornalamaya göre %53,59 daha düşük değerler verdiğini göstermiştir. Ayrıca MQL+Kry yönteminin kullanılması ile takım ömrü kuru tornalamaya kıyasla altı kat artmıştır.