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    Effects of Deep Cryogenic Treatment on the Wear Resistance and Mechanical Properties of AISI H13 Hot-Work Tool Steel
    (Springer, 2015) Cicek, Adem; Kara, Fuat; Kivak, Turgay; Ekici, Ergun; Uygur, Ilyas
    In 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.
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    Evaluation of machinability of hardened and cryo-treated AISI H13 hot work tool steel with ceramic inserts
    (Elsevier Sci Ltd, 2013) Cicek, Adem; Kara, Fuat; Kivak, Turgay; Ekici, Ergun
    The 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.
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    Performance of Multilayer Coated and Cryo-Treated Uncoated Tools in Machining of AISI H13 Tool Steel—Part 1: Tungsten Carbide End Mills
    (Springer, 2021) Çiçek, Adem; Kıvak, Turgay; Ekici, Ergün; Kara, Fuat; Uçak, Necati
    This paper focused on the performance of tungsten carbide end mills in machining of AISI H13 hot work tool steel under dry and wet conditions. The tool performance was evaluated in terms of resultant cutting force (Fc), average surface roughness (Ra) and tool life. In the milling tests, four categories of end mills were used: untreated (U), cryo-treated (CT), cryo-treated and tempered uncoated (CTT) and TiAlN/TiN multilayer coated (MLC). The tests were performed at four cutting speeds (80, 100, 120, 140 m/min), three feeds (0.08, 0.12, 0.16 mm/rev) and a depth of cut (2 mm). The test results showed that the lowest values of Fc and Ra were obtained with the use of MLC end mills. However, the cryogenic treatment was also effective on decreasing Fc and Ra. In addition, while the CTT end mills provided a slight improvement in tool life under dry conditions, they showed a remarkable improvement of 126.1% in comparison with the untreated ones under wet conditions. Although the CTT end mills exhibited a superior performance to U and CT ones, the MLC end mills were much more resistant to abrasive wear. This study is organized into two parts (WC-Co and HSS) to observe the effects of deep cryogenic treatment on performance of two different tool materials and to compare cryo-treated end mills with multilayer coated ones. This part is related to the cryogenic treatment of tungsten carbide end mills, whereas part two is regarding cryo-treated HSS end mills.
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    Performance of Multilayer Coated and Cryo-treated Uncoated Tools in Machining of AISI H13 Tool Steel—Part 2: HSS End Mills
    (Springer, 2021) Çiçek, Adem; Ekici, Ergün; Kıvak, Turgay; Kara, Fuat; Uçak, Necati
    This part of the study aimed to investigate the effects of cryogenic treatment applied to uncoated high speed steel (HSS) end mills on cutting forces (Fc), surface roughness (Ra), and tool life. The milling tests were performed at four cutting speeds (40, 50, 60, and 70 m/min), three feeds (0.018, 0.024, and 0.03 mm/rev), and a depth of cut (2 mm) under dry and wet conditions. Three categories of uncoated HSS end mills were used in the tests: conventional heat treated (CHT), cryo-treated (CT), cryo-treated and tempered uncoated (CTT), and TiAlN/TiN multilayer coated (MLC) end mills. The test results showed that the lowest values of Fc and Ra were measured with the use of MLC end mills. However, the cryogenic treatment provided in a reduction in Fc and Ra values. In addition, under wet conditions, the CTT end mills exhibited better performance than the CHT ones by 71.4%. The test results showed while cryogenic treatment is a useful and cheap application in steels, it does not have the ability to compete with coating technology in terms of tool life in milling of hot work tool steel. This paper is organized into two sections. In the first section, cutting performance of cryo-treated and multilayer coated end mills is evaluated. In the second section, performance comparison of cryo-treated WC-Co (Part 1), HSS (Part 2), and MLC end mills in milling of AISI H13 hot work tool steel is presented.
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    Response Surface Method Optimization of Hard Machining with Cryogenically Treated Cutting Tools: Surface Roughness, Cutting Force, Tool Wear, Rietveld Analysis, and Metallurgical Properties
    (Wiley-V C H Verlag Gmbh, 2024) Kara, Fuat; Takmaz, Aysun; Erkan, Omer; Filiz, Serhat
    The study consists of two stages: machinability tests and metallographic examinations. In the first stage of the study, response surface methodology (RSM) optimization was performed for the main-cutting-force (Fc) and average surface roughness (Ra) values obtained as a result of turning tests. In the second stage, the wear performance of cutting tool tips with and without deep cryogenic treatment was explained with the support of SEM images, EDX, XRD, and microhardness analyses. As a result of ANOVA analysis, it was found that the most effective parameter on Fc was the feed rate, with 78.89%. As a result of RSM-optimization, the lowest Fc value was found to be 339.99 N. The most effective parameter on Ra was found to be the feed rate at 69.38%. In terms of tool life, 15% and 11% improvements were achieved in uncoated and coated carbide cutting tools, respectively. As a result of Rieltveld's analysis, it was determined that cryogenic treatment increased the carbide percentages in the tools. As a result of microhardness measurements, it was observed that the hardness of uncoated and coated carbide tools increased by 4.6% and 5.15%, respectively, after cryogenic treatment.