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Hardness and dry sliding wear behaviour of Al7050 hybrid composites produced by stir casting

Srivallirani Katepalli, Venkateswara Rao M

Composites Theory and Practice

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2022

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R. 22, nr 3

150--159

EN

Hardness and dry sliding wear behaviour of Al7050 hybrid composites produced by stir casting The current study aims to investigate at the tribological properties of Al7050 reinforced with TiO2 and BN particles utilising a pin-on-disc apparatus. By means of the stir-casting process, MMCs were fabricated with three different weight percentages of TiO2 particles: 1, 3, and 5%, as well as various weight percentages of h-BN particles: 2, 4, and 6%. The volumetric wear rates and coefficients of friction were continuously recorded under normal loads of 20-40 N, sliding speeds of 2-4 m/s and for sliding distances of 1000, 1500 and 2000 m. Microstructural analysis revealed that the TiO2 and BN particles were uniformly dispersed throughout the Al7050 matrix with minimal agglomeration. The experimental data reveals that the tensile strength and Vickers hardness of the cast hybrid composites gradually improved by increasing the weight percentages of the TiO2 and h-BN reinforcing particles. The worn micrographs reveal that abrasion and delamination are the dominant wear mechanisms in the case of the hybrid composites. The composite containing 6 wt.% h-BN particles had the lowest coefficient of friction and wear rate at a normal load of 40 N, sliding speed of 4 m/s and for the sliding distance of 2000 m when compared to other composites. On the other hand, the composites with 2 wt.% h-BN particles had the highest coefficient of friction and wear rate. The XRD analysis showed the generation of strong interfacial reactions, which contributed to the hardness of the hybrid composites.

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Effect of h-BN solid nano lubricant on the dry sliding wear behaviour of Al-B4C nanocomposites

Harichandran R., Selvakumar N.

Archives of Materials Science and Engineering

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2016

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Vol. 77, nr 1

5--11

EN

Purpose: In this paper, three composites with different B4C content and fixed h-BN nanoparticles reinforced aluminium composites were fabricated through ultrasonic cavitation assisted casting. The role of the B4C and h-BN nanoparticles content on the mechanical and tribological properties of the aluminium composites was evaluated. This study presents the report on characterizion and evaluation of mechanical properties of h-BN and B4C nanoparticles reinforced aluminium composites. Design/methodology/approach: Al-B4C-h-BN composites are fabricated using stir and ultrasonic cavitation-assisted casting processes. The prepared composites are characterized using X-ray diffraction, Scanning Electron Microscopy and Energy Dispersive Spectroscopy. The dry sliding wear behaviour of the Al-B4C-h-BN composites are investigated using pin-on-disc wear test. Findings: The results of microstructural study reveal that uniform distribution, grain refinement and low porosity in composite specimens. The wear properties of the hybrid nanocomposites, containing 4 wt% B4C and 2 wt. % h-BN, exhibit the superior wear resistance properties as compared to unreinforced aluminium matrix. Practical implications: The interest in use of hexagonal boron nitride nanoparticles (h-BN) as solid nano lubricant for aluminium has been growing considerably due to its self lubricating properties.

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Właściwości użytkowe tworzyw z układu B4C–CrSi2–hBN

Rutkowski P., Klimczyk P.

Materiały Ceramiczne

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2013

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T. 65, nr 3

343--351

PL

W pracy przedstawiono wyniki dotyczące otrzymywania tworzyw zawierających osnowę z węglika boru. Do osnowy wprowadzano fazę syntezowanego krzemku chromu, który z jednej strony miał za zadanie obniżenie temperatury spiekania, a z drugiej podwyższenie odporności na kruche pękanie. Do tworzywa wprowadzono heksagonalny azotek boru w ilościach (2-8)% objętościowych w celu obniżenia współczynnika tarcia. Materiały otrzymano na drodze prasowania na gorącą w temperaturze o 150 ºC niższej niż dla tworzyw spiekanych w układzie B4C/h-BN. Wszystkie uzyskane tworzywa scharakteryzowano pod względem fazowym, strukturalnym, mikrostrukturalnym, właściwości sprężystych oraz właściwości mechanicznych. Otrzymano tworzywa o wytrzymałości na zginanie sięgającej 540 MPa, współczynniku krytycznej intensywności naprężeń 4,7 MPa•m1/2 oraz obniżonej w stosunku do czystego węglika boru wartości współczynnika tarcia i podwyższonej odporności na zużycie ścierne.

EN

In the paper, the results on the manufacturing boron carbide matrix materials were presented. The synthesized chromium silicide phase was added to the matrix to lower the sintering temperature and to increase the fracture toughness. Hexagonal boron nitride was introduced in a quantity of (2-8) vol.% to the composite as a solid lubricate. The materials were hot-pressed at the temperature of 150 ºC lower than used for the naturally sintered B4C/h-BN composites. The studied bodies were subjected to the phase and microstructural analysis, microstructural observations, and elastic and mechanical property measurements. The materials with a bending strength of 540 MPa and a fracture toughness of 4.7 MPam1/2 were manufactured. The lowered friction coefficient and lowered abrasion wear were recorded in comparison to the pure boron carbide material.

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Spiekanie tworzyw węglika boru zawierających dodatek heksagonalnego azotku boru

Rutkowski P.

Materiały Ceramiczne

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2013

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T. 65, nr 3

366--373

PL

W ramach niniejszej pracy przedstawiono badania nad wpływem aktywatorów spiekania, takich jak węglik chromu oraz krzemki chromu, a także dodatku stałego środka poślizgowego w postaci heksagonalnego azotku boru, na przebieg zagęszczania spiekanych tworzyw. W tym celu przeprowadzono badania przy pomocy wysokotemperaturowego dylatometru, umożliwiającego pomiar zmian wymiarów liniowych spiekanych tworzyw o osnowie węglika boru z dodatkami 5% obj. aktywatorów i (2-8)% obj h-BN. Określono zagęszczenie otrzymanych materiałów oraz zmiany składu fazowego w funkcji temperatury. Równolegle przeprowadzono próby prasowania na gorąco tych układów. Określono wpływ przyłożonego ciśnienia prasowania na zagęszczenie wytworzonych kompozytów. Przeprowadzono pomiar zagęszczenia, analizę fazową, strukturalną i mikrostrukturalną, a wyniki porównano z badaniami dylatometrycznymi.

EN

The influence of hexagonal boron nitride, chromium carbide and chromium silicide on densification of boron carbide polycrystals is studied. The first additive was used as a solid lubricant, the latter two were sintering additives, that enhance densification. A high-temperature dilatometer was used to run the measurements of linear dimension changes of the boron carbide based materials during sintering. The sintering additives were added in the quantity of 5 vol. % and the h-BN content was 2-8 vol.%. The densification of the obtained materials was determined. The phase composition changes were studied as a function of sintering temperature. Simultaneously, the trials of hot-pressing of the studied materials were made. The influence of the applied pressure on material’s densification during the sintering was determined. The densification measurements, phase and structural analysis, microstructural observations were made and compared with dilatometric data.