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Friction films analysis and tribological properties of composite antifriction self-lubricating material based on nickel alloy

Roszak Maciej Robert, Kurzawa Adam, Roik Tetiana, Gavrysh Oleg, Vitsiuk Iulia, Barsan Narcis, Pyka Dariusz, Bocian Mirosław, Jamroziak Krzysztof

Materials Science Poland

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2023

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Vol. 41, No. 3

1--17

EN

This article analyzes the composition and distribution of chemical elements in friction films and their effect on the tribological properties of the self-lubricating, high-temperature antifriction composite based on EP975 powder nickel alloy with CaF2 solid lubricant. Analysis of the chemical elements by energy-dispersive spectroscopy (EDS) showed their uniform distribution, on both the composite’s surface and the counterface’s surface. The alloying elements’ uniform distribution leads to a uniform distribution of the corresponding phases and structural elements in the antifriction film. This ensures high tribological properties at high temperatures. Analysis of the material’s tribological properties, by means of metallographic and micro-X-ray research confirmed the correctness of the technology for producing the composite. Solid lubricant CaF2, alloying elements, and their corresponding phases form the continuous antiscoring film. The film influences the antifriction properties formation during the friction process and provides a self-lubricating mode under the action of high temperature and oxygen. Antiscoring, self-lubricating CaF2 films minimize wear of the friction pairs and defend the contact surfaces against intensive wear. The dense antifriction films have smooth microtopography, which stabilizes the high-temperature friction unit operation. Thus, the self-lubrication mode is realized for a long exploitation time. Tribological properties analysis allowed us to determine the ranges of rational exploitation modes for the material being studied: a load up to 5.0 MPa, a slide speed from 0.3 to 1.0 m/s, a temperature up to 800°C, in the air. The results obtained opened the opportunity to control the antifriction film formation and the composite’s tribological properties by the choice of the initial ingredients while taking into account the operating conditions.

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Tribosynthesis of friction films and their influence on the functional properties of copper-based antifriction composites for printing machines

Olaleye Kayode, Roik Tetiana, Kurzawa Adam, Gavrysh Oleg, Pyka Dariusz, Bocian Mirosław, Jamroziak Krzysztof

Materials Science Poland

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2022

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Vol. 40, No. 4

147--157

EN

This article is devoted to research of the tribosynthesis mechanism of antifriction films and their influence on the functional properties of antifriction composites based on copper alloyed with nickel and molybdenum with the CaF2 solid lubricant additions for operation at rotation speeds of 3,000–7,000 rph and increased loads of 3.0–5.0 MPa in air. Studies have shown that antifriction films are complex, dynamically changing formations on the surfaces of the composite and counterface, developing according to the bifurcation mechanism. The antifriction layer is decisive in the formation of the friction pair's tribological high-level properties, which provide the self-lubrication mode of the friction unit. The formation and permanent presence of the anti-seize film is associated with a balanced wear rate of the film and its constant formation again on these worn areas at rotation speeds of up to 7,000 rph and loads of up to 5.0 MPa. Due to the steady self-lubrication mechanism, the copper-based composite has significant advantages over cast bronze CuSn5ZnPb, which can only work with liquid lubrication in the friction units of printing machines. The performed studies make it possible to choose rational modes for operation of new high-speed antifriction Cu-composites based on the friction films analysis, predicting their high functional properties.

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Mikrostruktura materiałów kompozytowych na osnowie stopu EN AW-2024 umacnianych cząstkami α-Al2O3

Kurzawa Adam, Kaczmar Jacek W.

Prace Instytutu Odlewnictwa

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2019

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Vol. 59, no. 1

3--13

PL

W pracy zostały przedstawione wyniki badań mikrostruktur materiałów kompozytowych wytwarzanych metodą infiltracji ciśnieniowej preform z cząstek ceramicznych α-Al2O3 stopem aluminium EN AW-2024. W badaniach mikroskopowych w szczególności oceniano jakość połączeń na granicach międzyfazowych osnowa-cząstki ceramiczne. Stwierdzono, że krzemionka (SiO2) stosowana do łączenia cząstek tlenku glinu w preformie powoduje wzbogacenie osnowy w krzem (Si), w części dyfundujący do stopu aluminium, który jednak pozostaje w osnowie w postaci skupisk SiO2, szczególnie w obrębie cząstek ceramicznych o dużym stopniu aglomeracji. Infiltracja porów otwartych preformy ceramicznej stopem EN AW-2024 o ograniczonej rzadkopłynności utrudnia proces infiltracji, pozostawiając lokalnie występującą porowatość. Propagacja pęknięć w materiale kompozytowym po badaniach właściwości mechanicznych następuje głównie po granicach międzyfazowych osnowa- -cząstka, szczególnie w miejscach o zwiększonej ilości rezydualnej krzemionki (SiO2) w osnowie. Na powierzchniach przełomów obserwuje się cząstki ceramiczne umocnienia α-Al2O3 o mocnym adhezyjnym połączeniu z osnową, które podczas tworzenia złomu ulegają pęknięciom.

EN

The paper presents the results of investigations into the microstructures of composite materials produced by pressure infiltration of preforms of ceramic α-Al2O3 particles with aluminium alloy EN AW-2024. In particular, the quality of the bonds at the interphase boundaries of matrix-ceramic particles was evaluated using microscopy investigations. It was found that silica (SiO2) used for bonding alumina particles in the preform causes an enrichment of the matrix in silicon (Si), which partly diffuses to aluminium alloy, yet remains in the matrix in the form of SiO2 concentrations, especially within ceramic particles with a high degree of agglomeration. The infiltration of open pores of ceramic preforms with EN AW-2024 alloy of limited flowing power hinders the infiltration process, resulting in local porosity. The propagation of cracks in the composite material after tests for mechanical properties occurs mainly along the interphase boundaries of the matrix-particle, especially in places with an increased residual amount of silica (SiO2) in the matrix. On the surfaces of the fractures ceramic particles of the α-Al2O3 reinforcement are observed, they form a strong adhesive bond with the matrix and crack during the formation of scrap metal.