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Dynamic impact wear and impact resistance of W-B-C coatings
Daniel, Josef ; Grossman, Jan ; Buršíková, V. ; Zábranský, L. ; Souček, P. ; Mirzaei, S. ; Vašina, P.
Coated components used in industry are often exposed to repetitive dynamic impact load. The dynamic impact test is a suitable method for the study of thin protective coatings under such conditions. Aim of this paper is to describe the method of dynamic impact testing and the novel concepts of evaluation of the impact test results, such as the impact resistance and the impact deformation rate. All of the presented results were obtained by testing two W-B-C coatings with different C/W ratio. Different impact test results are discussed with respect to the coatings microstructure, the chemical and phase composition, and the mechanical properties. It is shown that coating adhesion to the HSS substrate played a crucial role in the coatings.
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Impact resistence on nanocomposite Mo-B-C- and W-B-C coatings deposited using magnetron sputtering technique
Fořt, Tomáš ; Grossman, Jan ; Daniel, Josef ; Sobota, Jaroslav ; Dupák, Libor ; Buršíková, V. ; Zábranský, L. ; Souček, L. ; Mirzaei, S. ; Alishahi, M. ; Vašina, P. ; Buršík, Jiří
Recently, based on attractive mechanical properties of boride and carbide based X2BC ternary compounds (X = Mo, W and Ta) they became subjects of both theoretical calculations and experimental work. In the case of stoichiometric composition, X2BC with X = Mo, W and Ta are very promising candidates for protection of cutting and forming tools due to their unusually stiffness and moderate ductility.\nIn this work we focus on nanostructured Mo-B-C and W-B-C layers grown by magnetron sputtering on high speed steel (HSS) substrates. Mechanical properties of the layers were characterized by nanoindentation experiments in both static and dynamic loading regimes. Elastic modulus, indentation hardness and fracture resistance were evaluated and discussed. The fracture resistance of both Mo-B-C and W-B-C coatings was compared using both indentation and dynamic impact tests.\n
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Study of fracture toughness and wear resistance of thin MoBC coating under dynamic conditions
Buršíková, V. ; Grossman, Jan ; Fořt, Tomáš ; Souček, P. ; Zábranský, L. ; Buršík, Jiří ; Vašina, P. ; Dupák, Libor ; Sobota, Jaroslav
The aim of the present work was to study the mechanical properties of thin amorphous MoBC coatings and MoBC coatings consisting of nanocrystalline Mo2BC embedded in amorphous MoBC matrix. The hardness of the amorphous MoBC coatings (20 GPa) is comparable with the common amorphous diamond-like carbon coatings, however their elastic modulus as well as fracture toughness and ductility are significantly higher. Magnetron sputtering of three targets, B4C, C and Mo, for MoBC was used for coatings preparation. The aim of this work was to study the mechanical and tribological properties of MoBC coatings deposited on high speed steel substrate. The classification of MoBC coatings was performed using an impact tester in a dynamic mode and enabled us to predict the limit load causing the coating destruction.
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Dynamic impact tester of hard thin coatings
Grossman, Jan ; Dupák, Libor ; Fořt, Tomáš ; Sobota, Jaroslav
An impact test has been used to evaluate the impact wear resistance of nanostructured hard coatings using a system developed at the Institute of Scientific Instruments in collaboration with the Brno University of Technology. After the test, wear scars were evaluated by means of scanning electron microscope, spectral analyses and profilometer. The impact test offers an important new method for the determination of both the fracture toughness and wear behaviour of hard thin coatings.
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Studium mechanických vlastností DLC tenkých vrstev deponovaných v jedno a dvoufrekvenčním kapacitním výboji
Buršíková, V. ; Stoica, A. ; Sobota, Jaroslav ; Grossman, Jan ; Fořt, Tomáš ; Klapetek, P. ; Buršík, Jiří ; Bláhová, O.
Nanostructured diamond-like carbon coatings were deposited on several different substrate materials (silicon, glass, polycarbonate and steel) in single (13.56 MHz) and dual capacitive r.f. discharges (LF=100-300kHz, HF =13.56 MHz). The objective of our study was to find the optimum combination of the high and low frequency (continuous or pulsed) excitation enabling to cover uneven substrate surfaces and significant lowering of the internal stress in films.
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Studium mechanických vlastností gradovaných amorfních DLC povlaků deponovaných PECVD
Buršíková, V. ; Stoica, A. ; Sobota, Jaroslav ; Grossman, Jan ; Fořt, Tomáš ; Klapetek, P. ; Buršík, Jiří ; Peřina, Vratislav ; Bláhová, O.
For optimisation of performance of the coating there is necessary to optimise the following materials parameters: the elastic modulus, hardness, surface strength, film fracture toughness and film-substrate adhesion. We proposed to protect the substrate surface with graded coating, which has monotonically graded elastic modulus and Poisson's ratio.
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Tribologické chovaní tvrdých uhlíkových kompozitních vrstev
Fořt, Tomáš ; Grossman, Jan ; Sobota, Jaroslav ; Vítů, T. ; Novák, R.
Carbon hard composite coatings were exposed to dynamical load and high temperature pin-on-disc CSM Tribometer. To evaluate the impact resistance of thin hard composite coating in dynamic loading wear applications an impact test was used. The sliding tests in air were carried out in the range from room temperature to 500 °C with controlled relative humidity. Hardness, elastic modulus and fracture toughness of deposited coatings were studied by indentation technique using Fisherscope H100 tester.
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