Wyniki wyszukiwania - BazTech

1

Study on the Microstructure, Electrical and Mechanical Properties of Hot Pressing Cr-50 Mass% Ni Alloys Fabricated by Addition of Various Ratios of Nanosized Ni Powders

Huang Jhong-Ren, Chang Shih-Hsien, Liao Cheng-Liang

Archives of Metallurgy and Materials

|

2022

|

Vol. 67, iss. 3

955--961

EN

In this work, nanosized Ni (nNi) powders of 50 nm are mixed with Cr and Ni submicron-powders (600 nm) to fabricate Cr-50 mass% Ni alloys by vacuum hot pressing. In order to evaluate the influence of the nanosized Ni powders, different amounts of nanosized Ni powders are added to produce the Cr-(50-x) mass% Ni-x mass% nNi alloys (x = 0, 10, 20, and 30). The hot pressing was maintained at 1275°C, 48 MPa for 1 h. The microstructure evaluation, mechanical, and electrical properties were performed. The results reveal that mechanical and electrical properties are enhanced when increasing the nNi addition. The Cr-20 mass% Ni-30 mass% nNi presents the highest relative density of 96.53% and the electrical conductivity of 2.18×104 Scm-1, moreover, the hardness and transverse rupture strength values increase to 76.1 HRA and 1217 MPa, respectively. Moreover, a more homogeneous microstructure and a decrease in the mean grain size to 3.15 μm are acquired. Significantly, this fabrication procedure (adding 30 mass% nanosized nickel powders) results in the optimal microstructure, electrical and mechanical properties of submicron-structured Cr-(50-x) mass% Ni-x mass% nNi alloys.

2

Dispersion mechanism-induced variations in microstructural and mechanical behavior of CNT-reinforced aluminum nanocomposites

Doğan Kemal, Özgün Muhammed Ihsan, Sübütay Halit, Salur Emin, Eker Yasin, Kuntoğlu Mustafa, Aslan Abdullah, Gupta Munish Kumar, Acarer Mustafa

Archives of Civil and Mechanical Engineering

|

2022

|

Vol. 22, no. 1

art. no. e55, 2022

EN

The combination of powder metallurgy and ball milling method has been widely regarded as the most beneficial route for producing multi-walled carbon nanotubes (MWCNTs)-reinforced aluminum matrix composites. In this study, the effects of different milling times (1, 2, 4, and 8 h) on the structural, morphological, and crystallographic properties of MWCNTs-reinforced Al7075 composite powders were characterized by particle size analyzer, Raman spectroscopy, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), and X-ray diffraction (XRD). After the morphological and structural characterization of the milled powders, the microstructural and mechanical properties of the hot-pressed composites were evaluated using an optical microscope, SEM, density, and Brinell hardness measurements. Considering milled powder characterization, the MWCNTs were gradually distributed and embedded within the matrix as the milling time increased. Milling for 8 h resulted in a minimum level of particle size (11 µm) with shortened and uniformly dispersed CNTs. Brinell hardness of the composite increased from 91 to 237 HB -a ⁓%160 after 8 h of milling. Such a remarkable increment in hardness could be attributed to several concurrent strengthening effects related to dispersion, solution, grain refinement, and Orowan looping mechanisms. However, relative density results revealed that the composite produced by 2 h milled powders exhibited the highest density (%99.96). The observed differences between hardness and density results were ascribed to powders’ deteriorated packing and sintering behavior due to an increment in the hardness of particles and variation in particle size range and morphology, which resulted from following different milling protocols.

3

Fly ash/phenolic resin composite for brake pad application : fabrication, materials and thermal properties

Savetlana Shirley, Lubis Asnawi, Aditya Lingga, Irfan Muhammad, Siadari Dedi, Efendi Gunawan, Yusuf Muhammad, Jefri Hel

Composites Theory and Practice

|

2020

|

R. 20, nr 3-4

95--101

EN

Nowadays, many parts of automotive components are made of composites. One application of composites is brake lining material in braking systems. Fly ash is waste from burning coal in the power plant industry. Fly ash was added to a polimer matrix to enhance the wear properties of the composite. The appropriate temperature and pressure for composite fabrication were chosen from the composite which has the highest hardness. The addition of 30 wt.% fly ash to the phenolic resin matrix resulted in the lowest specific abrasion of the composite. Additions of graphite, iron powder and nitrile butadiene rubber increased the specific abrasion of the fly ash/phenolic resin composite. Scanning electron microscope micrographs showed the distribution and agglomeration of the particles in the phenolic resin matrix. The addition of fly ash to the phenolic resin matrix also increased the temperature resistance of the composite. Thermogravimetric analysis shows that the starting temperatures for decomposition of the composite constituents shifted to higher temperatures as the fly ash content increases.

4

Processing and Characterization of Fe-Cu-Ni Sinters Prepared by Ball Milling and Hot Pressing

Borowiecka-Jamrozek J.

Archives of Metallurgy and Materials

|

2020

|

Vol. 65, iss. 3

1157--1161

EN

The main objective of the present work was to determine the effect of powder composition on microstructure and properties of iron-base materials used as matrices in diamond impregnated tools. The Fe-Cu-Ni powders premixed and ball-milled for 30 hours, were used for the experiments. The influence of manufacturing process parameters on microstructure and mechanical properties of produced sinters was investigated. Sintering was done by hot-pressing technique in graphite mould. The powders were consolidated to a virtually pore-free condition during 3 minutes hold at 35 MPa and 900°C. Investigations of the sintered materials included: density, hardness, static tensile test and X-ray diffraction (XRD) analysis. Microstructural and fractographic observations were also made with a scanning electron microscope (SEM). The obtained results indicate that the sintered parts have a high density, close to the theoretical value, good plasticity, relatively high hardness and yield strength, and are characterized by a coarse-grained microstructure.

5

Hot pressing of tungsten monocarbide nanopowder mixtures by electroconsolidation method

Gevorkyan Edwin, Rucki Mirosław, Chishkala Vladimir, Kislitsa Maksim, Siemiątkowski Zbigniew, Morozow Dmitrij

Journal of Machine Construction and Maintenance - Problemy Eksploatacji

|

2019

|

no. 2

67--73

EN

The paper presents theoretical and experimental results in the field of the manufacturing of cemented tungsten carbide materials. The important issue of avoiding any additional substances like plasticizers was challenged in order to reach the maximal possible density of sintered material while keeping its purity. To solve the problem, the electroconsolidation method of hot pressing supported by direct current was applied. The respective apparatus was constructed that enabled WC nanopowders to be sintered under pressure and high temperature during a very short time of ca. 3 minutes. In the experiments, because of the short heating time, grain size of the sintered bulk WC increased insignificantly, in general, remaining smaller than 1 μm. Similarly, sintering under hot pressing with direct current, a mixture of 3% by weight Y2O3 stabilized ZrO2 and 50% by weight WC, produced a fine structure with a uniformly distributed WC grains. The applied electric field led to the formation of a temperature gradient around the pores, with a favourable impact on the compaction of large pores and an increase in the final density of the bulk material. The experimental research confirmed that the main mechanism of the densification of nanodispersed powders of tungsten monocarbide was a locally inhomogeneous diffusion-viscous flow with intergranular slipping.

PL

W artykule przedstawiono rozważania teoretyczne i wyniki badań eksperymentalnych dotyczących wyrobów z węglików wolframu uzyskiwanych metodą spiekania. Podjęto próbę rozwiązania jednego z problemów, jakim jest obecność substancji uplastyczniających, która wspomagając proces spiekania jednocześnie utrudnia uzyskanie maksymalnej gęstości gotowego materiału. W celu rozwiązania tego zagadnienia zastosowano metodę eloktrokonsolidacji, polegającą na spiekaniu wspomaganym przepływem prądu elektrycznego. Skonstruowana aparatura umożliwia spiekanie proszków węglika wolframu w bardzo krótkim czasie rzędu 3 minut. W badaniach eksperymentalnych wykazano, że krótki czas oddziaływania wysokiej temperatury na wzrost ziaren w strukturze spieku jest nieznaczny i rozmiary ziaren pozostają na poziomie 1 μm. Podobnie mieszanka 3% masy Y2O3 stabilizowanego ZrO2 z 50% masy WC umożliwiła uzyskanie spieku o strukturze zawierającej równomiernie rozłożone ziarna węglika wolframu. Zastosowanie prądu elektrycznego powoduje wytworzenie gradientu temperatury wokół porów, korzystnie wpływając na proces kompakcji i zwiększając wynikową gęstość spieku. Wyniki eksperymentów potwierdziły główne założenia stosowane w opisie teoretycznym kompakcji nanodyspersyjnych proszków węglika wolframu.

6

Właściwości fizyczne, mechaniczne i tribologiczne osnowy w spiekanych narzędziach metaliczno-diamentowych otrzymanych metodami HP i SPS

Bączek E.

Mechanik

|

2018

|

R. 91, nr 10

846--849

PL

Przedstawiono wyniki badań właściwości fizycznych, mechanicznych i tribologicznych materiałów, stanowiących osnowę w spiekanych narzędziach metaliczno-diamentowych otrzymanych metodami SPS (spark plasma sintering) i HP (hot pressing). Mielone proszki na bazie żelaza skonsolidowano do gęstości względnej powyżej 97% w temperaturze 900°C, pod ciśnieniem 35 MPa i w czasie 3 min. Otrzymane spieki badano również pod kątem odporności na zużycie ścierne w obecności trzech i dwóch ciał. Wykazano, że materiały otrzymane metodą HP charakteryzują się wyższą gęstością, twardością oraz odpornością na zużycie ścierne w porównaniu z materiałami otrzymanymi metodą SPS.

EN

Metal matrix composites were prepared by hot pressing (HP) and spark plasma sintering (SPS) techniques. Ball-milled ironbase powders were consolidated to near full density by these methods at 900°C. The physical and mechanical properties of the resulting composites were investigated. The specimens were tested for resistance to both 3-body and 2-body abrasion. The composites obtained by HP method (at 900°C/35 MPa) had higher density, hardness and resistance to abrasion than those obtained by SPS method.

7

Technological properties of metallic-diamond tools manufactured by SPS process

Bączek E.

Mechanik

|

2018

|

R. 91, nr 12

1140--1143

EN

This paper presents the results of the technological properties of impregnated diamond tools fabricated via spark plasma sintering (SPS) during the process of grinding and cutting of highpurity oxides ceramics (ZrO2) stabilized with Y2O3 or MgO. As a metal matrix the water atomized tin bronze and steel-based matrix was used. After sintering, an analysis of microstructure was conducted using scanning electron microscopy. The resulting materials were tested for the apparent density determined by Archimedes’ method, Rockwell hardness (scale B), Young’s modulus, as well as for the technological properties. The performance results of obtained diamond composites were compared with commercial diamond wheel fabricated by HP (hot pressing), usually employed in the grinding of ceramics. Results showed that diamond tools based on Cu-Sn and steel, obtained by SPS, may be successfully used as a matrix in the impregnated diamond tools for cutting or grinding of high-purity oxides ceramics.

PL

Przedstawiono wyniki badań właściwości fizycznych, mechanicznych i użytkowych narzędzi diamentowych wytworzonych metodą SPS (spark plasma sintering) w procesie szlifowania i cięcia półwyrobów z zaawansowanej ceramiki technicznej korundowej i cyrkonowej stabilizowanej tlenkiem itru (Y2O3) lub magnezu (MgO). Jako materiał osnowy zastosowano rozpylany wodą proszek brązu cynowego oraz stal stopową. Wykazano, że materiały zaproponowane na osnowę zapewniają uzyskanie wysokich właściwości użytkowych narzędzi diamentowych otrzymanych metodą SPS w porównaniu z narzędziami diamentowymi otrzymanymi metodą prasowania na gorąco (HP).

8

Microstructure and phase composition of NiAl-CrB2 composite powders used for plasma spraying

Poliarus O., Morgiel J., Umanskyi O., Szlezynger M., Pomorska M., Bobrowski P., Szczerba M.

Composites Theory and Practice

|

2018

|

R. 18, nr 2

121--124

EN

The preparation of powder agglomerates used in the plasma spray deposition processes, and especially their homogeneity, turned out to be highly important at the moment when the phase ratio in the composite coatings began to differ from that in the starting materials. The present experiment was aimed at comparing the microstructure and phase composition of hot pressed or sintered NiAl and CrB2 powders. The use of SEM and XRD methods showed that only sintering leads to a reaction of the chromium diboride with the intermetallic matrix. As a result of this process, Ni0.5Cr1.5B3 phase precipitates on the CrB2 particles. Consequently, the agglomerates formed after crushing the compacts obtained by sintering are much more homogeneous than those formed by hot pressing.

PL

Przygotowanie aglomeratów proszków wykorzystywanych w procesach natryskiwania plazmowego, a w szczególności ich ujednorodnienie, okazało się wysoce istotne w momencie, gdy skład powłok kompozytowych zaczął się znacząco różnić od stosunku udziałów proszków wyjściowych. Obecny eksperyment był nakierowany na porównanie mikrostruktury i składu fazowego proszków NiAl oraz CrB2 spiekanych w stanie stałym pod ciśnieniem (hot pressed) oraz z przetopieniem osnowy metalicznej (sintered). Zastosowanie mikroskopii skaningowej i dyfraktometrii rentgenowskiej wykazało, że tylko przetopienie osnowy prowadzi do reakcji pomiędzy nią a dwuborkiem chromu. W rezultacie tego procesu dochodzi do wydzielania na CrB2 fazy typu Ni0.5Cr1.5B3. Aglomeraty powstałe po rozdrobnieniu spieków uzyskanych na drodze z przetopieniem osnowy są znacznie bardziej jednorodne niż te otrzymane z wykorzystaniem prasowania na gorąco.

9

Effect of Post-Heat Treatment on Microstructure and Mechanical Properties of Cu-Fe-Co Powder Alloy Fabricated by Hot Pressing

Çelik E., Aslan A. K.

Archives of Metallurgy and Materials

|

2018

|

Vol. 63, iss. 1

371--377

EN

In this study, the powder mixture which consists of Cu-Fe-Co was produced by using the method of hot pressing technique. In addition, effect of heat treatment process on microstructure and mechanical properties of this alloy was investigated. Following the hot pressing process applied on the samples, heat treatment was carried out at 950°C for two different dwelling times (90 and 180 minutes). Measured density values were considered as physical characteristics, while hardness and fracture strength values were considered as mechanical characteristics. It was observed that porosity rates of hot pressed samples were decreased by increasing of temperature and pressing parameters. In this study it was observed that Cu was spread in matrix and filled the micro porosities. Hardness values were determined to be decreased as a result of grain growth after heat treatment process. That 4 fold increased elongation % values which were achieved by TRS experiments were observed as well.

10

The Application of a Ball-milled Fe-Cu-Ni Powder Mixture to Fabricate Sintered Diamond Tools

Borowiecka-Jamrożek J., Konstanty J., Lachowski J.

Archives of Foundry Engineering

|

2018

|

Vol. 18, iss. 1

5--8

EN

This article discusses results of an analysis of mechanical properties of a sintered material obtained from a mixture of elemental iron, copper and nickel powders ball milled for 60 hours. The powder consolidation was performed by hot pressing in a graphite mould. The hot pressing was carried out for 3 minutes at 900 °C and under a pressure of 35 MPa. The sintered specimens were tested for density, porosity, hardness and tensile strength. Their microstructures and fracture surfaces were also examined using a scanning electron microscope (SEM). The study was conducted in order to determine the suitability of the sintered material for the manufacture of metal-bonded diamond tools. It was important to assess the effects of chemical composition and microstructure of the sintered material on its mechanical properties, which were compared with those of conventional metal bond material produced from a hot-pressed SMS grade cobalt powder. Although the studied material shows slightly lower strength and ductility as compared with cobalt, its hardness and offset yield strength are sufficiently high to meet the criteria for less demanding applications.

11

A Thermomechanical Model of an Elastic Particle in a Metallic Matrix

Lachowski J., Borowiecka-Jamrozek J. M.

Archives of Foundry Engineering

|

2018

|

Vol. 18, iss. 2

79--83

EN

This paper deals with numerical and analytical modelling of a diamond or silicon particle embedded in a metallic matrix. The numerical model of an elastic particle in a metallic matrix was created using the Abaqus software. Truncated octahedron-shaped and spherical-shaped diamond particles were considered. The numerical analysis involved determining the effect of temperature on the elastic and plastic parameters of the matrix material. The analytical model was developed for a spherical particle in a metallic matrix. The comparison of the numerical results with the analytical data indicates that the mechanical parameters responsible for the retention of diamond particles in a metal matrix are: the elastic energy of the particle, the elastic energy of the matrix and the radius of the plastic zone around the particle. An Al-based alloy containing 5% of Si and 2% of Cu was selected to study the mechanical behaviour of silicon precipitates embedded in the aluminium matrix. The model proposed to describe an elastic particle in a metallic matrix can be used to analyze other materials with inclusions or precipitates.

12

Odporność korozyjna prasowanych na gorąco nanokrystalicznych stopów tantalu

Sopata P., Koper J. K., Jakubowicz J.

Ochrona przed Korozją

|

2017

|

nr 11

365--367

PL

W pracy zaprezentowano wyniki badań odporności korozyjnej nanokrystalicznego tantalu oraz jego stopów. Dodatkami stopowymi były niob, molibden oraz wolfram. Materiałem wyjściowym były proszki metali, które poddano mechanicznej syntezie. Po 48 h mechanicznej syntezy materiał sprasowano na gorąco. Przeprowadzono badania odporności korozyjnej w trybie potencjodynamicznym, w płynie Ringera. Na postawie krzywych polaryzacji określono, że najgorszą odpornością korozyjną charakteryzuje się stop tantalu z niobem, a najlepszą stop tantalu z molibdenem. Bardzo dobre właściwości korozyjne zmierzono również dla stopów Ta-W. Wyniki porównano z czystym tantalem nanokrystalicznym, który charakteryzuje się gęstością prądu korozyjnego o 2–3 rzędy wielkości większą (gorszą odpornością korozyjną) od najlepszych nanokrystalicznych stopów Ta-Mo oraz Ta-W.

EN

The paper describes the results of corrosion resistance study of the nanocrystalline tantalum and its alloys. Alloying additives were niobium, molybdenum and tungsten. The starting materials were in the form of the metal powders which were then used in mechanical alloying synthesis. After 48 h of synthesis materials were hot pressed. The corrosion resistance was measured using the potentiodynamic mode in Ringer’s solution. The polarization curves show that the worst resistance has tantalum- niobium alloys and the best resistance has tantalum-molybdenum alloys. Significantly good properties for Ta-W alloy were measured. The results were compared with pure nanocrystalline tantalum which is characterized by 2–3 orders of magnitude higher corrosion current density (worst corrosion resistance) than the best nanocrystalline Ta-Mo and Ta-W alloys.

13

Warstwowe kompozyty Ti/Al/Ti otrzymane metodą dyfuzyjnego łączenia

Bednarczyk P., Szczepanik S., Nikiel P.

Obróbka Plastyczna Metali

|

2017

|

T. 28, nr 1

7--16

PL

Aluminium często jest używane do projektowania kompozytów warstwowych. Stosowane są wyroby z aluminium w postaci blach, czy też w postaci materiału typu „plaster miodu”. Do wytwarzania płaskich wyrobów warstwowych stosuje się między innymi procesy przeróbki plastycznej, metodę wybuchowego łączenia lub klejenie lekkiego rdzenia z wytrzymałą i sztywną metaliczną okładziną. Rdzeń takiego materiału jest wykonywany w postaci materiałów spienionych o strukturze porowatej lub materiałów typu plaster miodu. Okładziny wykonuje się natomiast ze stopów metali lekkich takich, jak aluminium i tytan. Całkowicie metaliczna konstrukcja może być osiągnięta poprzez zgrzewanie dyfuzyjne, ale uzyskuje się wówczas zwiększenie jej masy. W artykule przedstawiono wyniki badań możliwości zastosowania dyfuzyjnego łączenia do wytwarzania kompozytu warstwowego stop tytanu – proszek aluminium – stop tytanu w procesie prasowania na gorąco. Prasowanie realizowano w trzech etapach. Do wytworzenia kompozytu użyto blachy tytanowej ze stopu Ti6Al4V o grubości 1 mm oraz proszku aluminium, o wielkości cząstek mniejszej od 250 μm. Proces prasowania prowadzono w temperaturze 450oC, stosując nacisk prasowania 80 MPa. Podczas tego procesu otrzymano warstwę przejściową o grubości od 4 do 8 μm. Po trzecim prasowaniu osiągnięto zadawalającą wartość wytrzymałości na zginanie kompozytu wynoszącą 890 MPa, niewiele niższą od granicy plastyczności stopu Ti6Al4V, przy wytrzymałości na ścinanie połączenia 51 MPa. Problem dyfuzyjnego łączenia w warstwie przejściowej jest związany z utlenianiem aluminium i zmianą kształtu zagęszczonego podczas prasowania na gorąco proszku aluminium.

EN

Aluminium is frequently used to designing of a layered composites, as a sheet or honeycomb components. Layered, flat composites are fabricated using metal forming processes and explosive bonding, or adhesive bonding of light core with strong and rigid metallic facings. The cores of these materials are often made from porous, foamed structure or honeycomb. Facings are fabricated from light metal alloys, like aluminium and titanium. An all metal construction can be achieved by diffusion bonding, with a weight penalty. Feasibility of fabrication of composites by hot pressing, up to three applications, of a titanium alloy – aluminium powder – titanium alloy sandwich beams by diffusion bonding was demonstrated. TiAl4V sheet with thickness 1mm and aluminium powder with particle size less than 250 μm were used: temperature 450oC, compression stress 80 MPa. A continuous interfacial layer with thickness from 4 to 8 μm was produced. After third pressing, 51 MPa shear strength was attained with the flexural stress, 890 MPa, slightly below the yield stress of Ti6Al4V. Problems of bonding of an in the interfacial zone are associated with oxidation of aluminium and shape change of the being densified aluminium powder during hot pressing.

14

Sintered FeCuRe Alloys Produced from Commercially Available Powders

Borowiecka-Jamrozek J.

Archives of Metallurgy and Materials

|

2017

|

Vol. 62, iss. 3

1713--1720

EN

This paper discusses the mechanical properties of materials fabricated from commercially available powders designed for use as a metal matrix of diamond-impregnated composites. The powders with the catalogue numbers CSA and CSA800 produced in China were tested under laboratory conditions. The specimens were fabricated in a graphite mould using hot pressing. The materials were analysed for density, porosity, hardness and static tensile strength. A scanning electron microscope (SEM) was employed to observe the microstructure and fracture surfaces of the specimens. The experimental data was used to determine how the chemical composition of the powders and the process parameters affected the microstructure and properties of the materials. The properties of the sintered materials produced from the Chinese powders were compared with the properties reported for specimens fabricated from cobalt powder (Co SMS). Even though the hot pressed CSA and CSA800 powders had inferior mechanical properties to their cobalt analogue, they seem well-suited for general-purpose diamond-impregnated tools with less demanding applications.

15

Kucie w plastycznej matrycy intermetalików TiAl

Szczepanik S., Bednarczyk P.

Rudy i Metale Nieżelazne Recykling

|

2016

|

R. 61, nr 3

121--125

PL

Przedstawiono wyniki badań materiałów Ti-Al otrzymanych z mieszanki proszków przez prasowanie, a także w procesie samorozwijającej się syntezy SHS i dodatkowym odkształceniu w plastycznej matrycy. Po odkształceniu w plastycznej matrycy nastąpiło zwiększenie gęstości wyrobów oraz poprawa ich twardości i wytrzymałości na zginanie. Otrzymane materiały o porowatości 2,54 i 3,89% mają strukturę złożoną z ziaren fazy γ czyli TiAl, oraz płytkowych ziaren fazy γ i α2-Ti3Al.

EN

The influence of hot forging in a fluid die of hot pressed and of SHS Ti-Al powder preforms on structure and properties was investigated. Processing increased the density, with the materials having 2.54 and 3.89% porosity, respectively. The structures comprised γ-TiAl grains and γ and α2-Ti3Al platelets. Hardness was 183 ±34 HV10 for the previously hot pressed materials and 147 ±3 HV10 for SHS performs, and bends strengths were 146 MPa and 247 MPa, respectively.

16

Mechanical and thermal properties of tungsten carbide – graphite nanoparticles nanocomposites

Kornaus K., Gubernat A., Zientara D., Rutkowski P., Stobierski L.

Polish Journal of Chemical Technology

|

2016

|

Vol. 18, nr 2

84--88

EN

Previous studies concerning pure tungsten carbide polycrystalline materials revealed that nanolayers of graphite located between WC grains improve its thermal properties. What is more, pressure-induced orientation of graphene nano platelets (GNP) in hot pressed silicon nitride-graphene composites results in anisotropy of thermal conductivity. Aim of this study was to investigate if addition of GNP to WC will improve its thermal properties. For this purpose, tungsten carbide with 0.5–6 wt.% of GNP(12)-additive underwent hot pressing. The microstructure observations performed by SEM microscopy. The anisotropy was determined via ultrasonic measurements. The following mechanical properties were evaluated: Vickers hardness, bending strength, fracture toughness KIc. The influence of GNP(12) addition on oxidation resistance and thermal conductivity was examined. It was possible to manufacture hot-pressed WC-graphene composites with oriented GNP(12) particles, however, the addition of graphene decreased both thermal and mechanical properties of the material.

17

Mechanical properties of pressure sintered alumina-graphene composites

Rutkowski P., Klimczyk P., Jaworska L., Stobierski L., Zientara D., Tran K.

Materiały Ceramiczne

|

2016

|

T. 68, nr 2

168--175

EN

The work concerns the alumina-graphene materials sintered by two different pressure methods. The preparation route of the matrix-graphene mixture was discussed in the paper. The prepared compositions with different amount of graphene were hot-pressed or spark plasma sintered. The influence on uniaxial pressure during the sintering process on the microstructure was studied by the SEM microstructural observations and ultrasonic measurements. The work presents also the results of measurements of elastic and mechanical properties. Wear tests were made and friction coefficients determined by the ball-on-disk method.

PL

Praca dotyczy materiałów korund-grafen spiekanych za pomocą dwóch metod ciśnieniowych. Dyskusji poddano metodę przygotowania mieszaniny złożonej z proszku osnowy i grafenu. Mieszaniny o różnej zawartości grafenu prasowano na gorąco lub konsolidowano w warunkach spiekania wspomaganego polem elektrycznym. Wpływ jednoosiowego prasowania podczas spiekania na mikrostrukturę zbadano, stosując obserwacje mikrosrukturalne SEM i pomiary ultradźwiękowe. Praca zawiera również wyniki pomiarów właściwości sprężystych i mechanicznych. Test odporności na zużycie i pomiary współczynników tarcia wykonano za pomocą metody kula na dysku.

18

Optimization of the wear resistance of AA2024 matrix composites fabricated with hot pressing

Ovali I., Karakoç H., Çinici H.

Journal of Achievements in Materials and Manufacturing Engineering

|

2016

|

Vol. 79, nr 1

19--23

EN

Purpose: In the present study, the effects of B4C reinforcement volume fraction (% 5-15-20) on the abrasive wear properties of AA2024 matrix composites produced with hot pressing methods were investigated. Design/methodology/approach: As-received samples were also used for comparison. AA 2024 powder was mixed with B4C-SiC-Al2O3 particles by a three dimensional mechanic mixer for 30 minutes. Mixed powder was pressed under 60 MPa at room temperature in the steel mold by unidirectional. Steel mold kept in the furnace at 550ºC after the pre-pressing for 30 minutes. Samples were pressed in heated mold under 100 Pa. The wear tests were carried out using a pin-on-disk wear tester by sliding at sliding speeds of 1.2 m/s against silicon carbide paper. Normal loads of 10, 20 and 30 N at constant sliding speed at room temperature. Findings: The experimental result showed that B4C volume fraction significantly influence the wear behavior of AA2024 matrix composites produced with hot pressing methods. Originality/value: It was also found that the wear resistance of AA2024 matrix composites produced with hot pressing methods increases with increasing B4C volume fraction. The highest weight loss was obtained in the unreinforced matrix material.

19

LMO Ceramics Microstructure

Bruś B., Zarycka A.

Archives of Metallurgy and Materials

|

2016

|

Vol. 61, iss. 2A

857--862

EN

The aim of this work was to characterize the microstructure of LMO type ceramics. The ceramics obtained by the free sintering at two temperatures 1473 K and 1573 K and two sintering times 6 and 12 h was the test material. One series was also obtained by the hot pressing method for a comparison. In all the cases the material synthesis was conducted by the solid-state reaction method at 1173 for 24 h. Photographs of the specimen fractures were taken by a scanning electron microscope to characterize the microstructure of the ceramics obtained in a more detailed way. The VISILOG 4 system, enabling to calculate a lot of parameters characterizing the material microstructure, such as e.g.: a number of grains on the unit area, an average grain size, shape indexes of the grains in question, was used as well. It allows determining a grain size distribution, and a frequency of presence of grains with the specific shape index. By analyzing a set of the parameters obtained an influence of the technological conditions on the microstructure of the material in question, and on its properties and applicability at the same time can be determined.

20

Properties of Sinters Produced from Commercially Available Powder Mixtures

Borowiecka-Jamrozek J., Lachowski J.

Archives of Foundry Engineering

|

2016

|

Vol. 16, iss. 4

37--40

EN

This paper discusses the mechanical properties of a material fabricated from commercially available metal powder mixtures designed for use as a metal matrix of diamond impregnated composites. The mixtures with the catalogue numbers CSA and CSA800 provided by a Chinese producer are suitable for experimental laboratory testing. The specimens were fabricated in a graphite mould using hot pressing. The material was tested for density, porosity, hardness, and tensile strength under static loading. A scanning electron microscope (SEM) was used to analyze the microstructure and cleavage fracture of broken specimens. It was essential to determine how the chemical composition and the fabrication process affected the microstructure and properties of the material. The properties of the sinters were compared with those of hot pressed specimens fabricated from sub-micron size cobalt powder (Cobalt SMS). Although the as-consolidated material is inferior to cobalt, it displays a favourable combination of hardness, yield strength and ductility, and seems to have a great potential for moderate and general purpose applications.