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Öğe Effects of Deep Cryogenic Treatment on the Wear Resistance and Mechanical Properties of AISI H13 Hot-Work Tool Steel(Springer, 2015) Çiçek, Adem; Kara, Fuat; Kıvak, Turgay; Ekici, Ergün; Uygur, İlyasIn this study, a number of wear and tensile tests were performed to elucidate the effects of deep cryogenic treatment on the wear behavior and mechanical properties (hardness and tensile strength) of AISI H13 tool steel. In accordance with this purpose, three different heat treatments (conventional heat treatment (CHT), deep cryogenic treatment (DCT), and deep cryogenic treatment and tempering (DCTT)) were applied to tool steel samples. DCT and DCTT samples were held in nitrogen gas at -145 degrees C for 24 h. Wear tests were conducted on a dry pin-on-disk device using two loads of 60 and 80 N, two sliding velocities of 0.8 and 1 m/s, and a wear distance of 1000 m. All test results showed that DCT improved the adhesive wear resistance and mechanical properties of AISI H13 steel. The formation of small-sized and uniformly distributed carbide particles and the transformation of retained austenite to martensite played an important role in the improvements in the wear resistance and mechanical properties. After cleavage fracture, the surfaces of all samples were characterized by the cracking of primary carbides, while the DCT and DCTT samples displayed microvoid formation by decohesion of the fine carbides precipitated during the cryo-tempering process.Öğe Evaluation of machinability of hardened and cryo-treated AISI H13 hot work tool steel with ceramic inserts(Elsevier Sci Ltd, 2013) Çiçek, Adem; Kara, Fuat; Kıvak, Turgay; Ekici, ErgünThe positive effects of deep cryogenic treatment on the wear resistance of cutting tools and workpiece material are well known; however, no information has been reported about the effect on the machinability of cryo-treated tool steel in hard turning. In order to investigate the effects of cryogenic treatment on the machinability of hardened and cryo-treated tool steel, a number of investigations were performed on the hard turning of cryo-treated AISI H13 hot-work tool steel with two ceramic inserts under both dry and wet cutting conditions. Three categories of the hot-work tool steel were turned in the machinability studies: conventional heat treated (CHT), cryo-treated (CT) and cryo-treated and tempered (m). Experimental results showed that the lowest wear and surface roughness (Ra) values were obtained in the turning of the CTT samples. Additionally, in terms of main cutting force (Fc), surface roughness (Ra) and tool wear, Ti[C, N]-mixed alumina inserts (CC650) showed a better performance than SiC whisker-reinforced alumina inserts (CC670) under both dry and wet cutting conditions. The use of cutting fluid slightly improved the machinability of the tool steel. (C) 2013 Elsevier Ltd. All rights reserved.Öğe Evaluatıon Of The Effects Of Cuttıng Parameters On The Surface Roughness Durıng The Turnıng Of Hadfıeld Steel Wıth Response Surface Methodology(2014) Ekici, Ergün; Uzun, Gültekin; Kıvak, TurgayHadfield çeliği (X120Mn12) sahip olduğu mükemmel aşınma direncinden dolayı mühendislik uygulamalarında yaygın olarak kullanılmaktadır. Bu çalışmada Hadfield çeliğinin tornalanmasında kesme parametrelerinin yüzey pürüzlülüğü üzerindeki etkileri araştırılmıştır. Deneyler 80, 110, 140 m/dak kesme hızı, 0.2, 0.3, 0.4 mm/dev ilerleme ve 0.2, 0.4, 0.6 mm kesme derinliğinde kaplamalı karbür takımlar kullanılarak gerçekleştirilmiştir. Halfield çeliğinin işlenebilirliğinin değerlendirilmesinde yanıt yüzey yöntemi (RSM) kullanılarak bir model oluşturulmuştur. Kesme parametrelerinin yüzey pürüzlülüğü üzerindeki etkilerinin belirlenmesinde merkezi tümleşik tasarım (CCD) ve varyans analizi (ANOVA) kullanılmıştır. Deneysel çalışma sonrasında oluşturulan modelle, yüzey pürüzlülüğü üzerinde kesme parametrelerinden ilerlemenin % 90,28 katkı oranı ile en etkili parametre olduğu ortaya konulmuştur. İlerlemenin artmasıyla yüzey pürüzlülüğünün arttığı görülmüştür. Yüzey pürüzlülüğü üzerinde etki bakımından ilerlemeyi % 3,12 katkı oranı ile kesme hızı, % 1,7 katkı oranı ile de kesme derinliği takip etmiştir.Öğe An Experimental and Statistical Evaluation of The Cutting Parameters on The Machinability of Hadfield Steel(Gazi Univ, 2016) Kıvak, Turgay; Uzun, Gültekin; Ekici, ErgünThe effects of cutting tool coatings and cutting parameters (cutting speed, feed rate) on the cutting forces and surface roughness during the turning of Hadfield steel were investigated in this study. Cutting experiments were made on a CNC lathe under dry cutting conditions by employing CVD TiCN/Al2O3/TiN-, PVD TiAlN- and PVD TiAlN/AlCrO-coated cementite carbide inserts. Four different cutting speeds (100, 140, 180, 220 m/min), two different feed rates (0.2, 0.3 mm/rev) and a constant cutting depth of 0.8 mm were used as the cutting parameters. At the end of the tests, cutting force and surface roughness results were subjected to variance (ANOVA) and multiple regression analyses. The experimental results showed that the PVD TiAlN coating was superior to the CVD TiCN/Al2O3/TiN and PVD TiAlN/AlCrO coatings with respect to cutting force and surface roughness. The correlation coefficients of the statistical model developed at the end of the analysis were R-2=0.994 and R-2=0.996 for the cutting forces and surface roughness, respectively. The feed rate was found to be the most effective parameter on the cutting forces and surface roughness, with contribution ratios of 91.31% and 94.79% respectively.Öğe Experimental and Statistical Investigation of the Machinability of Al-10% SiC MMC Produced by Hot Pressing Method(Springer Heidelberg, 2014) Ekici, Ergün; Samtaş, Gürcan; Gülesin, MahmutIn this study, during the machining of metal matrix composites produced by a hot pressing method in CNC milling, the effects of cutting parameters and coating type on the surface roughness were experimentally and statistically investigated. The production of composite samples was accomplished by hot pressing, in which Al was used as the matrix element and 10 % SiC particles were chosen for the reinforcing phase. In the machining of samples, three different cutting tools (uncoated, multi-layered and Nano TiAlN coated), three different cutting speeds (60, 78, 101 m/min) and three different feed rates (0.04, 0.08 and 0.12 mm/rev) were employed. Full factorial (3(3)) experimental design was chosen for the statistical investigation of the cutting parameters and parameter interactions. The response surface method was used in the mathematical modelling of the surface roughness obtained from the experiments and in the optimisation of cutting parameters. At the end of the study, the cutting tool's wear was evaluated and the wear was discussed by comparison with similar studies.Öğe Experimental investigations of damage analysis in drilling of woven glass fiber-reinforced plastic composites(Springer London Ltd, 2010) Işık, Birhan; Ekici, ErgünThis paper presented a new comprehensive approach to select cutting parameters for damage factor in drilling of glass fiber-reinforced polymer (GFRP) composite material. The influence of drilling on surface quality of woven GFRP plastic composite material was investigated experimentally. Drilling tests were carried out using carbide drills of 8 mm in diameter at 50, 70, and 90 m/min cutting speeds and at 0.06, 0.12, and 0.18 mm/rev feed rates. Damage factor was investigated based on hole entrance and exit. Analysis of variance (ANOVA) test was applied to the experimental results. The compared values were employed by Duncan test to identify which groups were significantly different from other groups.Öğe Optimization of drilling parameters using Taguchi technique and response surface methodology (RSM) in drilling of AISI 304 steel with cryogenically treated HSS drills(Springer, 2015) Çiçek, Adem; Kıvak, Turgay; Ekici, ErgünIn this study, the effects of cryogenic treatment and drilling parameters on surface and hole quality were investigated in the drilling of AISI 304 stainless steel under dry drilling conditions. The control factors to provide better surface roughness (Ra) and roundness error (Re) were determined using the Taguchi method. RSM was also used to determine interactions among the control factors. In addition, analysis of variance was employed to determine the most significant control factors on the surface roughness and roundness error. Three drill categories (conventional heat treatment-CHT, cryogenic treatment-CT, cryo-tempering-CTT), cutting speeds, and feed rates were considered as control factors, and an full factorial design with a mixed orthogonal array was selected for experimental trials. As a result, it was found that the feed rate and cutting speed were the most significant factors on the surface roughness and roundness error with percentage contributions of 83.07 and 64.365 % respectively. The predictive quadratic models were derived by the RSM to obtain the optimal surface roughness and roundness error as a function of drilling parameters and heat treatments applied to the drills.Öğe Performance of cryogenically treated M35 HSS drills in drilling of austenitic stainless steels(Springer London Ltd, 2012) Çiçek, Adem; Kıvak, Turgay; Uygur, İlyas; Ekici, Ergün; Turgut, YakupIn this study, performance of cryogenically treated M35 high speed steel (HSS) twist drills in drilling of AISI 304 and 316 stainless steels was evaluated in terms of thrust force, surface roughness, tool wear, tool life, and chip formation. To present the differences in tool performance between untreated and treated drills, and machinability between AISI 304 SS and AISI 316 SS, a number of experiments were performed at different combinations of cutting speed, and feed rate. As the results of the conducted experiments, the treated drills showed better performance than untreated drills in terms of thrust force, surface roughness, and tool wear and tool life for both types of stainless steels. Tool lives of treated HSS drills in drilling of AISI 304 SS and AISI 316 SS improved 32% and 14%, respectively, when compared with untreated drills. Experimental results also showed that machinability of AISI 304 SS was harder than the machinability of AISI 316 SS.
