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EN
Purpose: The mechanical alloying (MA) method has been chosen to manufacture tool gradient materials with high disproportion of cobalt matrix portion between core and surface layer. Design/methodology/approach: The following research studies have been carried out to elaborate a new group of sintered tool gradient materials, tungsten carbide with cobalt matrix, to elaborate their fabrication technology and to determine their structure and properties: a fabrication technology of mixtures and the formation technology of tungsten carbide gradient materials with cobalt matrix WC-Co was applied and elaborated; sintering conditions were selected experimentally, ensuring the best structure and properties; phase and chemical composition of the sintered gradient WC-Co materials was determined using EDX; the structure of sintered gradient WC-Co materials was investigated using scanning microscopy; mechanical and physical properties of sintered gradient WC-Co materials was determined: hardness, resistance to abrasive wear, resistance to brittle cracking. Findings: The presented research results confirm that the methods of mixing tungsten carbide in cobalt matrix an important effect upon the grain size of mixture. But it is not possible to determine the changes in grain size distribution. The larger particles break down rapidly that the product becomes more uniform. Practical implications: The material presented in this paper is characterized by very high hardness of the surface and relative ductility of the core. Originality/value: The obtained results show the possibility to manufacture TGMs on the basis of different portions of cobalt reinforced with hard ceramics particles in order to improve the abrasive resistance and ductility of tool cutting materials.
2
Content available WC-5Co Cemented Carbides Fabricated by SPS
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EN
New graphite tools were designed and produced to fabricate a semi-finished product from which nine cutting inserts were obtained in one spark plasma sintering process. As a result, WC-5Co cemented carbides were spark plasma sintered and the effect of various sintering parameters such as compacting pressure, heating rate and holding time on the main mechanical properties were investigated. It was shown that WC-5Co cemented carbides spark plasma sintered at 1200°C, 80 MPa, 400°C/min, for 5 min are characterized by the best relation of hardness (1861±10 HV30 ) and fracture toughness (9.30 MPa·m1/2). The microstructure of these materials besides the WC ceramic phase and Co binder phase consists of a synthesized Co3 W3 C complex phase. Comparison with a commercial WC-6Co cutting insert fabricated by conventional powder metallurgy techniques shows that spark plasma sintering is a very effective technique to produce materials characterized by improved mechanical properties.
PL
Do wytworzenia płytek skrawających z proszków WC-Co zastosowano iskrowe spiekanie plazmowe. Uzyskane spieki poddano pomiarom gęstości i twardości oraz wyznaczono ich odporność na kruche pękanie. Dokonano obserwacji mikrostruktury. Wykazano, że wymaganą dla materiałów narzędziowych twardością odznaczają się płytki z proszku o ultradrobnej wielkości cząstek.
EN
For the production of cutting inserts, used spark plasma sintering method. The article include resulting density, hardness, fracture toughness and images of the microstructure cemented carbides (WC-Co). The cutting inserts fabricated from powder with ultrafine particles characterized a required for tool materials hardness.
4
Content available remote Multilayer and gradient PVD coatings on the sintered tool materials
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EN
Purpose: The paper presents investigation results of structure and properties of the multilayer and gradient TiN+(Ti,Al,Si)N+TiN nanocrystalline coatings deposited with the PVD method (CAE -Cathodic Arc Evaporation process) and in the combination of Al2O3 and TiN coatings in the CVD process on the substrate of cemented carbides,cermets, Al2O3+ZrO2, Al2O3+TiC, Al2O3+SiC(w) oxide ceramics and Si3N4 nitride ceramics. Design/methodology/approach: The structural investigation includes the metallographic analysis on thetransmission and scanning electron microscope, confocal microscope. Examinations of the chemicalcompositions of the deposited coatings were carried out using the X-ray energy dispersive spectrograph EDS, glow-discharge optical emission spectroscope GDOS, and using the X-ray diffractometer. The investigation includes also analysis of the mechanical and functional properties of the material: substrate hardness tests and microhardness tests of the deposited coatings, surface roughness tests, evaluation of the adhesion of the deposited coatings, cutting properties of the investigated materials. Findings: Deposition of the multicomponent gradient coatings with the PVD method, based on the Al and Si solid secondary solution in the TiN titanium nitride, isomorphous with the alternating pure titanium nitride TiN, on tools made from oxide, nitride ceramics and tool cermets, results in the increase of mechanical properties in comparison with uncoated tool materials, deciding thus the improvement of their working properties. Practical implications: Deposition of (Ti,Al,Si)N nanocrystalline coatings by the use of PVD method causes the increase of cutting properties of tools made of cermets for ca. 300% and of Al2O3+ZrO2 for ca. 100% comparing to adequately uncoated tools. Originality/value: Comparison of the wide range of modern sintered tool materials with wide unique set of PVD coatings.
EN
Wear resistance, which is one of the main technological quality features of machine parts and tools, is determined by the properties of their surface layer. The demand for high-quality products forces manufacturers to use modern structural and tooling materials as well as efficient and cost-effective methods of their treatment. The paper presents the results of research on selected properties of tools made of tool steels and sintered carbides, as well as parts made of aluminum alloy subjected to selected surface treatment processes, such as mechanical (grinding, turning, milling, burnishing) and thermo-chemical (nitriding, sulfonitriding) processes, and physical vapor deposition (PVD) of coatings. The presented results, including analyses of the surface geometric structure, microstructure, and microhardness, as well as tribological and machining properties of selected materials, indicate the possibility of improving the functional quality of tools and machine parts.
EN
The research aims to develop a novel and safer milling route to produce Hard Metals. Considering the risks associated with milling fine particles under organic solvents, especially the increased fire and explosion risks, we propose milling under aqueous milling media to diminish the risks associated with fire hazards, while maintaining the oxidation level at a minimum. The samples were sintered in an industrial sintering oven under vacuum at 1380°C subsequent to milling and drying. The characterisation of the materials has been done by X-ray diffraction, scanning electron microscopy, particle size analysis, optical microscopy, and a magnetometer. The obtained results indicate that appropriate properties of the powders after milling and drying as well as the desired biphasic (Co-WC) phases were obtained after sintering, thus proving the feasibility of such a route and diminishing specific fire hazards.
7
Content available remote Zastosowanie penetratorów z węglików spiekanych w amunicji średniokalibrowej
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PL
Omówiono sytuację w Polsce w zakresie produkcji węglików spiekanych i ich zastosowania oraz własności fizyko-mechaniczne uzależnione od zawartości kobaltowej fazy wiążącej i wielkości ziaren węglika wolframu. Przybliżono metodę obliczania współczynnika intensywności naprężeń Kic, charakteryzującego odporność węglików spiekanych na pękanie. Przedstawiono schemat pocisków nabojów typu MP. Opisano metody metalurgii proszków zastosowane do wykonania próbnych serii penetratorów w różnych gatunkach węglików spiekanych, ich własności fizykomechaniczne i strukturalne. Zaprezentowano wyniki strzelań z zastosowaniem wykonanych laboratoryjnie penetratorów, świadczące o możliwości skutecznego stosowania węglików spiekanych o odpowiednich własnościach w amunicji średniokalibrowej.
EN
The situation in Poland for sintered carbides manufacturing and their applications and physical-mechanical properties dependent on binding cobalt phase level and tungsten carbide grains size. The method for approximate calculation of the stress intensity coefficient Kic which characterizes the resistance of sintered carbides against breaking is included. Some outline drawings of MP rounds are presented. Method used in the metallurgy of powders applied to receive some prototype lots of penetrators on the base of different sintered carbides with their physical-mechanical-structural properties are described. The results of firing of rounds with application of penetrators received in the laboratory are presented as the prove that it is possible to use effectively of sintered carbides with relevant properties in the middle caliber ammunition.
PL
W pracy przedstawiono wyniki badań modelowych nad syntezą warstw tlenku glinu z dużą szybkością wzrostu w postaci pojedynczych grubych warstw gładkich o budowie drobnoziarnistej. Warstwy tego tlenku wstępnie syntezowano metodą MOCVD, stosując acetyloacetonian glinu o dużym stężeniu w zakresie temperatury 600÷800°C w argonie lub w powietrzu pod obniżonym ciśnieniem na podłożu ze szkła kwarcowego. Użycie przezroczystego szkła kwarcowego zamiast płytek wieloostrzowych węglików spiekanych umożliwiało m.in. łatwe ustalenie czy przy syntezie wystąpił niepożądany proces nukleacji homogenicznej. Wystąpienie tego procesu powodowało bowiem obniżenie przezroczystości warstw łatwe do zaobserwowania na szklanym podłożu. Na podstawie barw interferencyjnych można również ustalić szybko orientacyjną grubość warstw oraz jej zmiany. Otrzymane warstwy poddano następnie kontrolowanej krystalizacji w zakresie temperatury 850÷1000°C. Podano wyniki badań kinetyki wzrostu warstw, a także ich krystalizacji. Podano również wyniki badań budowy i własności warstw wygrzewanych i niewygrzewanych. Uzyskane wyniki badań będą pomocne przy syntezie warstw na docelowych podłożach z węglików spiekanych.
EN
This work shows results of investigations on model research of synthesis of aluminium oxide monlayers at their high growth rate. This layers should be characterized by fine-grained microstructure and high smoothness. Initially, aluminium oxide layers were synthesized in argon or air in the range of temperature of 600÷800°C using low preassure MOCVD method with aluminium acetyloacetonate as precursor. As a substrate it was used quartz glass. Using of quartz glass substrate instead of cemented carbide ones (it will be target substrates) made possible i.a. easy estimation if unfavorable process of homogeneous nucleation was present during the layer growth. Presence of this process causes decrease of transparency of the layer what is especially visible in the case of quartz glass substrate using. Basing of observation of interference colours of the layers the estimation of their thickness is possible and also changes of the layer thickness. Next, obtained layers were put to the controlled crystallization in the range of temperature of 850÷1000°C. In work it was shown results of investigations on kinetics of the growth of the layers and their crystallization. It was also presented results of research of the microstructure and properties of the annealed and not annealed layers. Obtained results of this investigations will be useful for the synthesis of aluminium oxide layers on target substrates.
9
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EN
Purpose: The goal of this work is to obtain the gradient materials based on the (W, Ti)C with high disproportion of cobalt matrix portion between core and surface layer. In this work is shown the structure and properties of Tool Gradient Materials (TGM). Design/methodology/approach: In presented study (W, Ti)C powder were mixed with cobalt powder. Prepared mixtures were heaped up, pressed at 300MPa and sintered in vacuum furnace at temperatures 1450*C. Produced gradient materials were studied by scanning electron microscope (SEM), light microscope. Hardness tests and density examination were also made. Findings: According to carried out researches it could be stated, that forming the gradient materials with highest portion of complex carbide (W,Ti)C 91-95%, using uniaxial unilateral pressing, could be possible after adding into each layer of mixtures 2% of paraffin lubricant. High diversification of cobalt matrix ratio in comparison with hard phases in subsequent layers of gradient materials leads to their deformation in as sintered state. In case of all gradient materials, mean hardness was equal about 1600 HV1. Whereas, hardness of lower cobalt matrix rich layers has value about 1450 HV1 which increases up to 1700 HV1 for lower layer of material rich with hard carbide phases. Practical implications: The Powder Metallurgy gives the possibility of manufacturing tools gradient materials characterised by very high hardness on the surface and relative ductility in core. Originality/value: In the work the manufacturing of TGM on the basis of different portion of cobalt matrix reinforced with hard ceramics particles carried out in order to improve the abrasion resistance and ductility of tool cutting materials.
PL
W artykule przedstawiono wyniki badań dotyczących wpływu ilości drobnoziarnistego węglika wolframu na wzmocnienie metalicznego spoiwa kobaltowego (Co) w węgliku spiekanym WC-8Co. Celem badań jest znalezienie optymalnego udziału węglika gruboziarnistego do drobnoziarnistego dla uzyskania poprawy właściwości mechanicznych i charakterystyk zużyciowych. Dla wszystkich próbek zastosowano jednakowy udział spoiwa, by zbadać jedynie wpływ udziału grubo- do drobnoziarnistego węglika w spieku. W wyniku przeprowadzonych badań stwierdzono, że dla proporcji 8:1 udziału węglika grubo- do drobnoziarnistego uzyskuje się najkorzystniejsze cechy użytkowe, tj.: twardość, udarność i odporność na pękanie. Ponadto poprzez dodanie do kompozytu inhibitorów wzrostu, np. węglika wanadu (VC) lub węglika chromu (Cr3C2), zwiększa się odporność na zużycie ścierne w stosunku do kompozytów bez dodatku inhibitorów.
EN
This study performs a comprehensive analysis concerning the amount of fine tungsten carbide (WC) grains needed for the appropriate reinforcement of the cobalt (Co) metallic binder in WC-8Co cemented carbides. The goal is to investigate the balance of coarse-to-fine grain distribution to achieve overall improvement of the material’s mechanical and wear properties. All Samales possessed the same WC-8Co binder content, therefore, allowing the role of grain size distribution to be tested. It was found that a ratio of 8:1 wt% of coarse to ultrafine grain WC yielded an appropriate balance between material hardness, fracture toughness, and rupture strength. Upon adding grain growth inhibitors vanadium carbide (VC) and chromium carbide (Cr3C2), the overall wear resistance is further improved compared to undoped composites when Samales are tested under abrasive wear conditions.
EN
WC–Co, WC–Co–Cr3C2 and WC–Co–TaC–NbC cemented carbides were spark plasma sintered and the microstructure and main mechanical properties of the obtained specimens were investigated. A series of WC–6Co cemented carbides was heated to the sintering temperature of 1400 °C at 200 and 400 °C/min at compacting pressures of 50 and 60 MPa. It was shown that the specimens spark plasma sintered at 400 °C/min and at 60 MPa possess the best mechanical properties. These parameters were applied for sintering WC–6Co cemented carbides with addition of grain growth inhibitors such as Cr3C2 and TaC–NbC. The influence of the grain growth inhibitors content was studied. The X-ray diffraction test results show that decarburization of the WC phase occurred and carbon deficient W2C and η (Co3W3C, Co6W6C) phases were formed during spark plasma sintering, wherein an increase in compacting pressure from 50 to 60 MPa results in a diminution in the carbon diffusion processes. The mechanical properties of the cemented carbides were defined. The best ratio of hardness and fracture toughness was obtained for WC–6Co–1Cr3C2: hardness was 1808 ± 19 HV30 and fracture toughness was 10.17 ± 0.27 MPa m1/2.
12
Content available remote Structure and properties of sintered tool gradient materials
75%
EN
Purpose: The main objective of the presented is to elaborate the fabrication technology of novel sintered tool gradient materials on the basis of hard wolfram carbide phase with cobalt binding phase, and to carry out research studies on the structure and properties of the newly elaborated sintered tool gradient materials. Design/methodology/approach: The following research studies have been carried out to elaborate a new group of sintered tool gradient materials, wolfram carbide with cobalt matrix, to elaborate their fabrication technology and to determine their structure and properties: a fabrication technology of mixtures and the formation technology of wolfram carbide gradient materials with cobalt matrix WC-Co was applied and elaborated; sintering conditions were selected experimentally: time, temperature and sintering atmosphere as well as isostatic condensation, ensuring the best structure and properties; phase and chemical composition of the sintered gradient WC-Co materials was determined using EDX, EBSD methods and qualitative X-ray analysis; the structure of sintered gradient WC-Co materials was investigated using scanning microscopy and transmission electron microscopy; mechanical and physical properties of sintered gradient WC-Co materials was determined: porosity, density, hardness, resistance to abrasive wear, resistance to brittle cracking. Findings: The presented research results confirm that the newly elaborated technology of powder metallurgy, which consists in sequential coating of the moulding with layers having the increasing content of carbides and decreasing concentration of cobalt, and then sintering such a compact, ensures the acquisition of the required structure and properties, including the resistance to cracking and abrasive wear of tool gradient materials, due to earned high hardness and resistance to abrasive wear on the surface as well as high resistance to cracking in the core of the materials fabricated in such a way. Practical implications: The material presented in this paper is characterized by very high hardness of the surface and relative ductility of the core. TGM with smooth changes of the cobalt phase in the material. Originality/value: The obtained results show the possibility to manufacture TGMs on the basis of different portions of cobalt reinforced with hard ceramics particles in order to improve the abrasive resistance and ductility of tool cutting materials.
PL
W artykule prezentowane są wyniki badań spieków węglika wolframu wytwarzanych w jednym procesie z mieszniny proszków (wolframu, węgla i kobaltu) przy wykorzystaniu metody PPS (Pulse Plasma Sintering) opracowanej na Wydziale Inżynierii Materiałowej Politechniki Warszawskiej. Z mieszaniny proszków: wolframu, węgla i kobaltu otrzymanow jednym procesie kompozyty WC-Co. Stosując spiekanie impulsowo-plazmowe otrzymano w czasie 480 s kompozyty WC-Co, którego wytworzenie w konwencjonalny sposób wynosi kilka godzin.
EN
The paper presents the results of examinations of tungsten carbide sinters produced of a mixture of tungsten, carbon and cobalt powders using the PPS method (Pulse Plasma Sintering), developed at the Faculty of Materials Engineering, Warsw University of Technology. With the use of the powder mixture, the WC-Co composites were produced during a single technological process. The WC-Co composite was produced by subjecting the elemental powers to sintering with high-current electric pulses for the time as short as 480 s, whereas with conventional methods the fabrication time of this composite amounts to several hours.
14
Content available remote Influence of hard ceramic particles on structure and properties of TGM
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EN
Purpose: The Powder Metallurgy route has been chosen to fabricate tool gradient materials with high disproportion of cobalt matrix portion between core and surface layer. In the paper structure and properties of TGM have been shown. Design/methodology/approach: SEM, light microscope, microhardness tests, density examination. Findings: According to carried out researches it could be stated, that forming the gradient materials with highest amount of complex carbide (W,Ti)C 90-95%, using uniaxial unilateral pressing, could be possible after adding into each layer of mixes 2 % of paraffin lubricant. High diversification of cobalt matrix ratio in comparison to hard phases in subsequent layers of gradient materials leads to their deformation in as sintered state. In case of all gradient materials, mean hardness was equal about 1600 HV1. Whereas, hardness of lower cobalt matrix rich layers brought values about 1450 HV1 and increased up to 1800 HV1 for lower layer of material rich with hard carbide phases. Practical implications: Material presented in this paper is characterized by very high hardness of the surface and relative ductility of core. TGM is a smoothly varying distribution of phases element composition. Originality/value: In the paper the manufacturing of TGM on basis of different portion of cobalt reinforced with hard ceramics particles carried out in order to improve the abrasion resistance and ductility of tool cutting materials.
PL
Celem badań było uzyskanie informacji, które pozwoliłyby na opracowanie nowej technologii syntezy monowarstw Al2O3 o regulowanej mikrostrukturze na węglikach spiekanych. Otrzymane w tych badaniach warstwy Al2O3-C będą stanowiły pośrednią warstwę, na której będzie syntezowana zewnętrzna warstwa Al2O3 bez węgla. Istotne jest, aby ta warstwa była cienka, ciągła, bardzo mało zróżnicowana w grubości i gęsta. Zadaniem pośredniej warstwy jest blokada dyfuzji kobaltu do syntezowanej czystej, zewnętrznej warstwy Al2O3 oraz blokada dyfuzji tlenu do podłoża trakcie syntezy warstwy zewnętrznej w powietrzu. Warstwy Al2O3 syntezowano z acetyloacetonianu glinu metodą CVD na szkle kwarcowym grzanym w piecu indukcyjnym w zakresie temperatury 800÷1000°C, stosując jako nośnik reagentów argon. Otrzymane warstwy Al2O3 zawierały węgiel, co powodowało ciemne zabarwienie warstw. Ciemne zabarwienie warstw świadczy, że węgiel nie jest w postaci pojedynczych atomów lecz skupisk, w których oprócz wiązań σ występują wiązania π. Warstwy otrzymywane w niskiej temperaturze poddawano sterowanej krystalizacji w temperaturze wyższej. Otrzymane warstwy w temperaturze powyżej 900°C były nanokrystaliczne (zawierały fazę α-Al2O3). Ze względu na to, że przebieg krystalizacji można regulować czasem i temperaturą procesu, można mieć większy wpływ na budowę, a przez to na własności warstw niż w procesie bezpośredniej syntezy w wysokiej temperaturze.
EN
The aim of the research was to obtain the information permissive on elaboration of new technology of synthesis of Al2O3 monolayers on cemented carbide tools. Presence of this process during the layer growth causes its cloudiness. It’s a result of formation of porous powders in gaseous phase. The object of an intermediate layer is blocking of cobalt diffusion to pure eternal layer and diffusion of oxygen to the substrate of cemented carbides during the synthesis process. Al2O3 layers were synthesised using aluminium acetyloacetonate on quartz glass by MOCVD method. In synthesis process argon was used as a carrier gas. The layers were deposited at 800÷1000°C. Obtained layers contained carbon, what caused their dark colour. It shows that carbon is present in the layers in form of clusters (presence of σ and π bondings). Layers obtained at lower temperature were treated controlled crystallization at higher temperature. Layers deposited at temperature above 900°C were nanocrystalline (contained α-Al2O3 phase). Process of the layers crystallization may be regulated by time and temperature of the process. Therefore we have an influence on microstructure and properties of deposited layers.
PL
Węgliki spiekane stanowią główną grupę materiałów narzędziowych, co wynika z ich dobrych właściwości skrawnych i wytrzymałościowych. Do wytwarzania węglików spiekanych stosowane są metody metalurgii proszków, spośród których za wysoce perspektywiczne uważa się spiekanie iskrowo-plazmowe. W pracy przedstawiono wyniki badań nad wpływem ciśnienia prasowania i szybkości nagrzewania na mikrostrukturę, a w konsekwencji na gęstość, twardość oraz odporność na kruche pękanie węglików spiekanych WC-6Co wytwarzanych metodą spiekania iskrowo-plazmowego. Spiekanie z wykorzystaniem urządzenia HP D 25-3 przeprowadzono w próżni w temperaturze 1200°C w czasie 10 min przy ciśnieniu prasowania wynoszącym 50 lub 60 MPa, z szybkością nagrzewania 200 lub 400°C/min. Z wytworzonych spieków wycięto, za pomocą wycinania elektroerozyjnego, próbki do pomiarów i badań. Pomiary gęstości przeprowadzono metodą Archimedesa zgodnie z normą ISO 3369:2006, natomiast pomiary twardości metodą Vickersa zgodnie z normą ISO 6507-1:2007. Wyznaczono odporność na kruche pękanie. Obserwacje mikrostruktury w kontraście elektronów wstecznie rozproszonych przeprowadzono z wykorzystaniem skaningowego mikroskopu elektronowego. Wykazano, że gęstość względna zwiększa się wraz ze zwiększeniem ciśnienia prasowania i szybkości nagrzewania, przy czym szybkość nagrzewania ma mniejsze znaczenie. Ponadto zwiększenie twardości wpływa na zmniejszenie odporności na kruche pękanie. Największą twardością, wynoszącą 1726 HV30, odznaczają się spieki wytworzone przy ciśnieniu prasowania wynoszącym 50 MPa z szybkością nagrzewania 400°C/min. Odporność na kruche pękanie tych materiałów wynosi 8,66 MPa·m1/2.
EN
Cemented carbides constitute the main group of tool materials due to their good cutting and strength properties. To produce cemented carbides powder metallurgy methods are used, among which spark plasma sintering is considered to be highly prospective. The paper presents the results of research on the effect of compaction pressure and heating rate on the microstructure and consequently on the density, hardness and fracture toughness of WC-6Co cemented carbides produced by spark plasma sintering. Sintering using an HP D 25-3 furnace was performed in vacuum at 1200°C for 10 min at a compaction pressure of 50 or 60 MPa and at a heating rate of 200 or 400°C/min. Samples for measurements and testing were cut by electrical discharge machining from the sintered compacts. Density measurements were carried out using the Archimedes method according to ISO 3369:2006 standard, while Vickers hardness measurements were performed according to ISO 6507-1:2007 standard. The fracture toughness was determined. Microstructure observations in backscattered electrons contrast were conducted using a scanning electron microscope. It was shown that the relative density increases with increasing compaction pressure and heating rate, whereby the heating rate is less important. In addition, an increase in hardness affects a reduction in the fracture toughness. The compacts sintered at the compaction pressure of 50 MPa at the heating rate of 400°C/min exhibited the highest hardness of 1726 HV30. The fracture toughness of these materials is 8.66 MPa·m1/2.
EN
Purpose: Goal of this work was to describe the propagation characteristic of cracks produced at the corners of Vickers indent and the toughness change in functionally graded WC-Co cemented carbide with high disproportion of cobalt matrix portion between core and surface layer. Design/methodology/approach: Investigations of toughness methods were developed during the investigations for tungsten carbide and cobalt, making it possible to obtain four materials and then their structure was determined. Findings: A wide variation in hardness and toughness has been obtained in WC-Co composites. The propagation characteristic of cracks produced at the corners of Vickers indent and the toughness change in functionally graded WC-Co cemented carbide with dual phase structure were investigated. It is shown that cracks tend to propagate both around and across WC crystal grain. The changes of toughness with the microstructure and an integrated strengthening effect, as well as high toughness characteristic of the tool gradient material are revealed. Practical implications: Material presented in this paper are characterized by very high hardness of the surface and relative ductility of core. The cobalt phase in obtained TGM material will changing smoothly. Originality/value: The Palmqvist test provides a useful method of measuring fracture toughness of material characterized by very high hardness of the surface and relative ductility of core.
18
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EN
Purpose: The purpose of the paper is to describe sintered Tool Gradient Materials manufactured by powder metallurgy process. The Powder Metallurgy method has been chosen to manufacture tool gradient materials with high disproportion of cobalt matrix portion between core and surface layer. Design/methodology/approach: Forming methods were developed during the investigations for tungsten carbide and cobalt, making it possible to obtain materials wits five layers in their structure. Findings: High diversification of cobalt matrix portion in comparison to hard phases in subsequent layers of gradient materials leads to their deformation in as sintered state. In case of all gradient materials, mean hardness was equal about 1750 HV1. Whereas, hardness of lower cobalt matrix rich layers is about 1548 HV1 and increased up to 2154 HV1 for lower layer of material rich with hard carbide phases. The porosity decreases along with the carbon content in these layers. Practical implications: Material presented in this paper is characterized by very high hardness of the surface and relative ductility of core. TGM with a smooth changes of the cobalt phase in the material. Originality/value: The obtained results show the possibility of manufacturing of TGM on basis of different portion of cobalt reinforced with hard ceramics particles carried out in order to improve the abrasion resistance and ductility of tool cutting materials.
19
Content available remote Węgliki spiekane i węglikostale w zaawansowanych elementach maszyn
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PL
Przeprowadzono badania struktury i właściwości węglików spiekanych i węglokostali. Przedstawiono zastosowania węglików spiekanych w łożyskach ślizgowych mieszadła reaktora polietylenu i węglokostali w powierzchni tnącej filiery granulatora polietylenu. Ze względu na konstrukcje, tolerancje wymiarowe, technologię i warunki eksploatacji zespoły te należą do bardzo zaawansowanych zespołów w budowie maszyn.
EN
The analysis of structure and properties of cemented carbides and PM Carbide Alloyed Composites has been done. The applications of cemented carbides in slide bearings of a mixer of a high-pressure polyethylene reactor, and carbide alloyed composites of a spinning nozzle of a die for polyethylene granulation surface. Because of a construction, dimension tolerances, technology, and operation conditions analyzed units belong to very advanced ones in machine building.
PL
Przeprowadzone w pracy badania są modelowe. Ich celem było opracowanie najlepszych warunków syntezy monowarstw Al2O3 o nanokrystalicznej budowie, przydatnych do nanoszenia ich z dużą szybkością wzrostu na węglikach spiekanych pokrywanych wstępnie pośrednią warstwą Al2O3-C. Zastosowanie podłoży ze szkła kwarcowego, ze względu na jego dużą przeświecalność, ułatwia uzyskanie informacji o jakości warstw, tj. grubości i jej zmienności, gęstości, z której wynikają inne cechy warstw, takie jak wytrzymałość mechaniczna, adhezja do podłoża. Istotny wpływ na gęstość może mieć proces nukleacji homogenicznej, w wyniku którego powstają porowate proszki o składzie zbliżonym lub takim samym jak syntezowane warstwy. Proszki te, osiadając na syntezowanej warstwie, powodują łatwe do zaobserwowania ich zmętnienie. Należy nadmienić, że stosowanie w badaniach rozwiniętego wyrażenia Grx/Rex 2 dodatkowo umożliwia szybkie ustalenie odpowiednich parametrów procesu. Warstwy tlenku glinu na szkle kwarcowym grzanym w piecu indukcyjnym syntezowano metodą CVD z acetyloacetonianu glinu w powietrzu w temperaturze 700÷1000°C. Otrzymano warstwy o dużej przeświecalności, gdy nie występował podczas ich syntezy proces nukleacji homogenicznej. Warstwy syntezowane w niższej temperaturze poddawano procesowi krystalizacji powyżej 900°C. Badano przebieg procesu krystalizacji w zależności od czasu i temperatury. Otrzymano warstwy o budowie nanokrystalicznej.
EN
Presented research is model. Its aim was to obtain the information helpful for elaboration of new technology of synthesis of Al2O3 monolayers on cemented carbides. Elaborated technology should make possible influence on microstructure of deposited layers. Al2O3-C layers obtained at this research will constitute an intermediate layer. An external layer will be Al2O3 layer without carbon. This layer should by thin, continuous, dense, uniform in thickness and well adherent to the substrate. Quartz glass is transparent and therefore we can easy visually estimate thickness of obtained layers, its changes and if the homogeneous nucleation process was present during the layer deposition. In this process porous powders are formed in gaseous phase (they composition is similar or the same as deposited layer) and they sink on the synthesized layer. Homogeneous nucleation process conduces synthesis of layers of low density. High density of synthesized layers is important because its results from it other properties, e.g. mechanical strength, adhesion to the substrate. Using of extended criterion of Grx/Rex 2 lets conduct the process of the layer synthesis in a such way in order to avoid appearance of this unfavourable process. Aluminium oxide layers were synthesised using aluminium acetyloacetonate at temperature of 700÷1000°C. Air was use as well as reactive and carrier gas. Obtained layers were transparent when during their synthesis process of homogeneous nucleation wasn’t present. Layers synthesized at lower temperature were treated controlled crystallization at temperature above 900°C. Dependence of crystallization process on time and temperature was investigated. Obtained layers were nanocrystalline. Their object is elaboration of optimum conditions for synthesis of Al2O3 layers on cemented carbides.
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