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PROJEKTOWANIE I WYTWARZANIE FUNKCJONALNYCH MATERIAŁÓW GRADIENTOWYCH*PBZ-KBN-100/T08/2003

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Zaawansowane zastosowania konstrukcyjne, elektryczne, chemiczne, optyczne, nuklearne czy biologiczne wymagają wysoko wydajnych, wielofunkcyjnych elementów roboczych, posiadających więcej niż jedną właściwość użytkową na wysokim poziomie. Materiały takie trudno jest otrzymać w układach monolitycznych objętościowych, wielowarstwowych lub nawet kompozytowych. Spowodowało to rozwój nowego rodzaju [...]

Multiscaled analysis of wear mechanism of titanium and carbon basis multilayer coatings

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Coatings are more and more frequently used to protect surface of mechanical parts exposed to wear loads. The ceramic hard coatings like TiN are of special interest due to their corrosion resistance and high hardness [1, 2]. The other suggested material for wear resistant coatings is amorphous carbon. The diamond like carbon coatings (DLC or a-C:H) are characterized by very low friction coefficient and biological inertness [3]. There is a tendency to connect the properties of different type of materials in multilayered composition [4, 5]. The TiN/Ti/a-C:H multilayer coatings might be applied for pump parts supporting, namely, artificial heart systems. The detailed microstructure description of wear mechanisms in coatings, particularly in multilayer systems are lacking. To enhance the cracking resistance properties of coatings it is high need to increase an energetic cost of propagating cracks. To do that, the multilayer systems are fabricated where metallic layers are placed in the sequence with ceramic ones [6, 7]. Deformation lines propagating through the multilayer coating contain plastic deformation in metallic layers and brittle cracking in ceramic ones. Brittle cracking in ceramics may be stopped at the interface. Anyway, there are some sorts of application wher[...]

Tailoring of multilayer structure to tribological conditions

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Wear is a result of one or complex processes like: erosion, abrasion, impact, metal-to-metal contact, oxidation, and corrosion. Several classification schemes of wear have been developed to understand wear processes. One or more fundamental wear mechanisms may play a crucial role in a real process including a mechanical damage [1]. In many devices, damage generally occurs by means of adhesive, abrasive, corrosive or fatigue wear [2]. The tribology-related engineering applications for highly stressed components require development of new multifunctional thin film systems providing superior mechanical, tribological, chemical etc. performance. It could be achieved by joining properties of different type of materials in multilayer coatings [3÷9]. Currently, a surface modification pays much attention. A set of alternate layers of hard and soft phases as well as appropriate buffer layer close to the substrate, can lead to coating quality improvement and increase adhesion to the substrate [10÷18]. Multilayer coatings are composed of alternately stacked layers of hard and soft phases with thicknesses of a few to tens of nanometers. A combination of alternate layers may lead to considerable hardness and high flexibility as well as good adhesion to substrates. Possible cracks propagation through ceramic coating can be stopped at the ceramic/metallic interface due to a plastic flow. Energy of brittle cracking is compensating by the plastic deformation. However, in some sorts of application, like tribological coatings for medical application, namely, surgical tools, an amount of metallic phase has to be limited. Otherwise, such coatings may lead to the metalosis, i.e. the metal ions adverse interaction with human organism. The titanium nitride (TiN) is of a special interest due to its corrosion resistance, high hardness and bio- compatibility [19, 20]. The other promising material for wear resistant application is amorphous hydrogenated ca[...]

Microstructure and its defect analysis of titanium nitride and chromium nitride multilayer tribological systems

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Multilayer tribological coatings on Ti/TiN; Cr/CrN and TiN/CrN basis were deposited by the Pulsed Laser Deposition (PLD) technique at room temperature using an industrially designed 4-beam multi-spot PLD evaporator. Coatings were built of 2, 8, 32 and 64 layers with the total thickness of 1 µm. Microstructure was studied using conventional and high resolution transmission electron micro[...]

A note on the kink bands in compressed Ni2MnGa single crystals

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In the last decade Ni-Mn-Ga single crystals had been a subject of intense structural and magnetic studies, because of their enormous magnetic shape memory effect (MSM), which is observed when the alloy possesses a tetragonal or orthorhombic crystal structure [1÷3]. Large interest has been paid to the Curie temperature and to the critical temperature of martensitic transformation, where upon cooling the high temperature cubic phase is replaced by the tetragonal (orthorhombic) structure [4, 5]. Recently, there has been focused a greater interest on the mechanical properties of the Ni2MnGa type alloys of cubic phase, because of their capability to adopt large plastic strains at high temperatures [6, 7] and hence the effect of the plastic deformation on the degree of deprivation of the MSM is also studied [8]. In this context, studies of the brittle-ductile transition which is observed in the cubic Ni2MnGa single crystals at elevated temperatures are of particular significance. However, as it was very recently reported in [9], Ni-Mn-Ga single crystals of both of the cubic and tetragonal structure, subjected to the room temperature compression are still capable to accommodate locally small plastic strains, before they fracture at the strength level of about 1 GPa. It seems important to make a proposal that the brittle-ductile transition in these alloys may be strongly correlated with temperature stability of the mechanism responsible for the accommodation of these small plastic strains. In this work, deformation geometry of the discussed accommodation mechanism will be shown in detail. Basing on the experimental observations of the Ni2MnGa single crystals compressed at 475 K it will be shown that the accommodation mechanism consists of a successive nucleation and further propagation of the kink bands and it is strongly correlated with the appearance of the mechanical instabilities on the stress-strain curve. The analysis presented i[...]

Optimization of Ti - Cr - N multilayer wear resistance coatings through microstructure control

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In the current work, multilayer coatings on Cr/CrN and TiN/CrN basis were deposited by the Pulsed Laser Deposition (PLD) technique at room temperature using an industrially designed 4-beam multi-spot PLD evaporator. Coatings were built of 2, 8, 32 and 64 layers with the total thickness of 1 ￿m . In the case of Cr/CrN, metallic layers are tough but soft and nitride layers are hard but [...]

Nanostrukturalne powłoki na bazie tytanu do kontaktu z krwią; diagnostyka strukturalna, adhezja komórek w warunkach hydrodynamicznych

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Odpowiedź komórek na obciążenia mechaniczne w warunkach ich oddziaływania z implantowanym materiałem jest ważnym elementem determinującym powodzenie implantu [1]. Zjawiska te występują szczególnie w systemach naczyniowych oraz mięśniowych. Komórki budujące naczynia krwionośne poddawane są ciśnieniu pulsacyjnemu przepływającej krwi. W celu określenia sił mechanicznych oddziałujących na komórki naczyniowe wprowadzonych zostało kilka dynamicznych testów in vitro. Większość z nich wykorzystuje relację pomiędzy adhezją komórek a naprężeniem ścinającym, występującym pomiędzy komórką a powierzchnią biomateriału. Z fizykochemicznego punktu widzenia, bio-adhezja dotyczy trzech składowych: komórek, stałego podłoża i ciekłego medium [2]. W ostatnim dwudziestoleciu liczne eksperymentalne [...]

Nowe tribologiczne powłoki wielowarstwowe typu Ti/TiN, Cr/CrN – mechanizm zużycia w próbie ball-on-disc

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Nowoczesny przemysł wymaga od inżynierii materiałowej nowych materiałów o podwyższonych, a często unikatowych właściwościach. Zastosowanie powłok w inżynierii materiałowej determinowane jest często technologią nanoszenia stosującą głównie metodę chemiczną (CVD) lub fizyczną (PVD) [1]. Ostatnio wprowadza się coraz częściej metody łączone - hybrydowe [2]. Azotek tytanu jest najbardziej poznanym i najszerzej wykorzystywanym materiałem tribologicznym spośród azotków metali grup przejściowych, stosowanych na twarde powłoki odporne na zużycie. Wymagania odporności na utlenianie w podwyższonej temperaturze wskazują na celowość zastosowania azotku chromu. Warstwy chromowe wytwarzają cienką pasywną warstwę tlenku, która zabezpiecza materiał przed dalszym utlenianiem. Obecnie rozwija si[...]

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