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1

On increasing powder carbon steels properties using activating additives

Dyachkova L.

International Journal of Applied Mechanics and Engineering

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2020

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Vol. 25, no. 2

192--201

EN

In this paper, the possibility of increasing powder carbon steels properties by activation of carbon diffusion into the iron base during sintering process due to the introduction of the thermally split graphite (TSG), macromolecular compounds (MC) and sodium bicarbonate was investigated. It was found that the introduction of these additives allows obtaining homogeneous structures at a sintering temperature of 100–200 °C lower than that traditionally used for sintering of powder carbon steels. Such structures provide increased mechanical properties of powder carbon steels. The addition ofsodium bicarbonate increases the diffusion rate of carbon into iron at a temperature of 950 C by 1.8 times, at 1000 °C by 1.5 times, and at 1100 °C by 1.2 times.

2

On the fractography and some strength properties of Fe-based sintered materials with multicomponent oxide microadditives

Feldshtein E., Michalski M., Adamczuk K., Dyachkova L.

International Journal of Applied Mechanics and Engineering

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2019

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Vol. 24, no. 4

224--229

EN

In the present paper, the effect of alumina and zirconia microadditives on the compressive strength and flexural strength of sintered Fe-based powder materials is shown. It was found that intercrystalline fractures, both plastic and brittle, are observed when bending. During compression, fractures are observed too, as well as flaking of thin nearsurface layers. The intensity of such flaking depends on the composition of the sintered material. Strength parameters of the materials studied also depend on additives composition and quantity. The lowest parameters are observed for a material that contains 1% alumina particulates. The compressive strength of a material containing zirconia particulates increases 3 times and the flexural strength 2 times.

3

On some mechanical properties and wear behavior of sintered bronze based composites reinforced with some aluminides microadditives

Feldshtein E., Kiełek P., Kiełek T., Dyachkova L., Letsko A.

International Journal of Applied Mechanics and Engineering

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2017

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Vol. 22, no. 2

293--302

EN

In the paper, the changes in some mechanical properties and wear behavior of CuSn10 sintered bronze and MMCs based on this bronze reinforced with composite ultrafine aluminide powders FeAl/15 % Al2O3, NiAl/15 % Al2O3 and Ti-46Al-8Cr are described. It was observed that the presence of aluminides in the MMCs leads to an increase in the hardness, but the flexural strength may increase or decrease depending on the type of aluminide. The presence of aluminides in the MMC reduces the wear rate considerably. It is decreased in the direction of FeAl/15 % Al2O3 → NiAl/15 % Al2O3 → Ti-46Al-8Cr aluminides and for the best MMC composition the advantage is about 20 times. In the MMCs wear process, micro-craters are formed on the contact surface and it is the principal reason of a decrease in the wear rate.

4

Tribological properties of sintered of bronze-based composites reinforced with Al-based hard particulares

Dyachkova L., Feldshtein E., Letsko A., Kiełek P., Kiełek T.

Composites Theory and Practice

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2017

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R. 17, nr 2

84--89

EN

This paper describes the changes in the tribotechnical properties of CuSn10 sintered bronze and MMCs based on this bronze reinforced with ultrafine composite Al-based powders. It was observed that the presence of hard particulates in the MMCs leads to a decrease in the friction coefficient and, particularly, wear rate. The presence of Al-based particulates in the MMC reduces the wear rate considerably. It decreases in the direction of FeAl → NiAl → Ti-Al-Cr particulates and for the best MMC composition the gain is about 20 times. In the MMC wear process, micro-craters are formed on the contact surface and it is the principal reason for the decrease in the wear rate.

PL

W pracy zbadano zmiany właściwości tribotechnicznych spiekanego brązu CuSn10 oraz kompozytów metalowych na bazie tego brązy umocnionego twardymi cząstkami proszków na bazie aluminium: FeAl, NiAl oraz Ti-46Al-8Cr. Obecność w kompozycie twardych cząstek na bazie Al prowadzi do zmniejszenia współczynnika tarcia i intensywności zużycia. Temperatury w strefie styku są stabilne, maksymalne temperatury zaobserwowano w warunkach wzrastającego obciążenia. Intensywność zużycia zmniejsza się w kierunku FeAl → NiAl → Ti-Al-Cr cząstek i dla kompozytu o najlepszym składzie przewaga sięga 20 razy. Zasadniczą przyczyną zmniejszenia intensywności zużycia są mikrokratery powstające na powierzchniach styku.

5

Surface texture of sintered iron-graphite MMCs infiltrated by copper alloys after grinding

Feldshtein E., Dyachkova L.

Advances in Manufacturing Science and Technology

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2013

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Vol. 37, nr 4

69--76

EN

The influence of grinding conditions on surface texture of sintered FeGr1.2 metal matrix composites infiltrated by copper based alloys such as CuSn5 and CuSn5Pb2.5 is considered. The composition of MMC and parameters of grinding practically do not influence the texture of the treated surface after grinding using with white Al2O3 wheel. Conditions of sparking out have the decisive influence on the results of grinding. Four passes of sparking out reduce the vertical roughness parameters more than twice, mean width of the surface element RSm more than three times and material ratio of the profile Rmr(50) about twice.

PL

W pracy ustalono wpływ warunków szlifowania na strukturę geometryczną powierzchni spiekanych materiałów kompozytowych FeGr1.2, nasyconych stopami miedzi CuSn5 i CuSn5Pb2.5. Ustalono, że skład chemiczny kompozytu i parametry szlifowania nie wpływają na strukturę geometryczną powierzchni obrobionej ściernicą z elektrokorundu białego Al2O3. Warunki wyiskrzania mają natomiast decydujący wpływ na efekty szlifowania. Cztery przejścia wyiskrzania zmniejszają parametry pionowe chropowatości powierzchni ponad 2 razy, średnią szerokość elementów profilu ponad 3 razy i udział materiałowy profilu Rmr(50) ok. 2 razy.

6

Strength and tribological properties of sintered powder composite materials based on copper with addition of alumina and nickel oxide

Feldshtein E., Dyachkova L.

International Journal of Applied Mechanics and Engineering

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2012

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Vol. 17, no. 1

41-52

EN

In the paper, the influence of oxide addition on the strength and mechanical properties of a sintered powder material based on copper is described. The increase of alumina content in the composite sintered material leads to decreasing its strength. The most significant decrease of strength is observed when less than 5% of alumina is added to the total volume. A further increase of the alumina content practically leaves the bending strength unchanged and decreases the strength limit in compression insignificantly. The addition of mixture of 80% of the alumina and 20% of the nickel oxide increases the bending strength about 40 50 MPa, and also promotes the formation of a more homogeneous and fine-grained structure, as well as decreases material porosity. The average coefficient of friction of the "sintered composite material - hardened steel C45" pair practically did not change over time. The lowest coefficients of friction were observed for a material containing alumina addition. An addition of Motor Life Professional additive to the lubricant oil reduces the coefficient of friction for the material free of oxides more than 30%. The temperature of friction is reduced by 25÷30% and the rate of linear wear decreases 1.4 to 3 times.