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Öğe Cutting performance improvement of MTCVD coated cemented carbide inserts via appropriate heat treatment(Elsevier, 2020) Skordaris, Georgios; Bouzakis, Konstantinos Dionysios; Stergioudi, Fani; Kouparanis, Stefanos; Boumpakis, Apostolos; Bouzakis, A.The softening of cemented carbide at the elevated temperature of MTCVD processes results in significant reduction of their strength, and thus, high coating deformation during cutting. In this way, at interrupted cutting loads, as during turning cast iron, the cutting performance of MTCVD coated cemented carbide inserts degrades due to premature coating fatigue fracture. To overcome this problem, appropriate heat treatments of MTCVD coated inserts were conducted. The related temperatures and durations for improving the substrate properties were optimized considering obtained strength data of uncoated inserts variously heat treated and the turning performance of coated ones correspondingly heat treated. (C) 2020 CIRP. Published by Elsevier Ltd. All rights reserved.Öğe Determination of strain rate depended stress and strain fields in pvd coatings on cemented carbide inserts during the repetitive impact test(Trans Tech Publications Ltd, 2020) Bouzakis, Antonios; Skordaris, Georgios; Bouzakis, Konstantinos-Dionysios; Gökcen, Mehmet-Gökhan; Boumpakis, Apostolos; Batuk, Ahmet-Ugur; Sisman, SüleymanRecently, stress, strain, strain-rate dependent curves for cemented carbide have become an established tool for evaluating the mechanical properties. In this paper, related strain-rate dependent data of a K05 insert were employed to define the developed stress and strain fields occurring in the compound coating-substrate at impact forces of various durations. In this way, the occurring maximum strains at various impact loads and times were analytically calculated. These maximum values and related fatigue endurance coating strain-rate dependent limits were consequently used to validate published coating fatigue critical impact forces associated with certain impact times. © 2020 Trans Tech Publications Ltd, Switzerland.Öğe Effect of the crystallinity of diamond coatings on cemented carbide inserts on their cutting performance in milling(Elsevier Science Bv, 2019) Skordaris, Georgios; Bouzakis, Konstantinos Dionysios; Kotsanis, Tilemachos; Boumpakis, Apostolos; Stergioudi, Fani; Christofilos, Dimitrios; Woda, M.Micro-crystalline diamond (MCD) coatings were deposited on cemented carbide inserts at different temperatures using hot filament chemical vapor deposition technique. For investigating the effect of the developed diamond crystallinity on the fatigue strength and wear behaviour of the prepared MCD coated inserts, inclined impact tests and milling investigations were conducted correspondingly. Raman spectra were recorded for capturing the crystalline phases after the film deposition and their potential changes after the impact and milling experiments induced by the mechanical and thermal loads. Thus, the explanation of the cutting performance of the employed diamond coated inserts with various crystalline phases was enabled. (C) 2019 Published by Elsevier Ltd on behalf of CIRP.Öğe Stress, strain and strain-rate cemented carbide properties determined with a fem-supported evaluation of impact test imprints(Elsevier Sci Ltd, 2021) Bouzakis, Antonios; Skordaris, Georgios; Bouzakis, Konstantinos Dionysios; Gökçen, Mehmet Gökhan; Boumpakis, Apostolos; Batuk, Ahmet Uğur; Şişman, SüleymanCemented carbide materials are key in tool manufacturing, nowadays widely used in cutting, forming and other manufacturing processes. Commonly applied methods for obtaining their strain-rate dependent material properties are insufficient due to the high hardness, mechanical strength and low deformability. In this paper, we produce relevant data for stress-strain and strain-rate curves up to strain rates of approximately 200 s(-1) with the aid of a developed FEM-supported evaluation method for remaining imprints on cemented carbide surfaces after applying impact loads at various durations and magnitudes. Regarding the impact duration, the impact loads were dynamically generated via electromagnetic or piezoelectric devices. The attained data are relevant to several applications including calculations to determine the stress and strain fields developed in cemented carbide tools imposed by impact loads at various conditions.Öğe Wear and fatigue behavior of pvd and mtcvd ticn coated cemented carbide inserts in turning cast iron(Trans Tech Publications Ltd, 2020) Skordaris, Georgios; Bouzakis, Konstantinos-Dionysios; Stergioudi, Fani; Kouparanis, Stefanos; Boumpakis, Apostolos; Bouzakis, AntoniosTiCN coatings of the same chemical compositions were deposited on HW/K05-K20 cemented carbide inserts via physical (PVD) and medium temperature chemical vapor deposition (MTCVD) techniques. Nano-indentations coupled with appropriate FEM simulations were used for characterizing the film and substrate mechanical properties. Furthermore, uncoated cemented carbide substrates were annealed in vacuum at temperatures and durations corresponding to the related ones during the PVD and MTCVD process for recording the effect of the deposition temperature and duration on the substrate strength properties. Perpendicular and inclined impact tests at various loads were performed for checking the coating fatigue endurance and adhesion respectively. These material data were considered in FEM supported calculations for predicting the developed stress fields in the cutting edge during turning cast iron GG30 using the PVD and MTCVD TiCN coated inserts. According to the obtained result, both coatings possess the same stress-strain properties. Hereupon, the MTCVD coatings are characterized comparably to PVD ones by improved fatigue properties and adhesion strength. Although these properties contribute to an increased tool life in finishing turning, the significant reduction of the substrate strength properties, due to the elevated temperature during the MTCVD process, results in a premature coating failure and a consequent intensive wear evolution in roughing. © 2020 Trans Tech Publications Ltd, Switzerland.
