Study on the Tribological Performance of Copper-Based Powder Metallurgical Friction Materials with Cu-Coated or Uncoated Graphite Particles as Lubricants

The tribological performance of copper-based powder metallurgical material is much influenced by the interfacial bonding between the components and matrix. By adding Cu-coated or uncoated graphite particles as a lubricant, two types of copper-based powder metallurgical materials were prepared via spark plasma sintering (SPS). The hardness, relative density, and thermal conductivity of the two specimens were firstly measured. Using an inertial braking test bench and temperature measuring instrument, the average friction coefficients, instantaneous friction coefficients, and friction temperatures of the two specimens were tested under different test conditions, and the wear rates were calculated accordingly. Based on the analysis of surface morphologies and elements distribution after the tests, the mechanisms of wear and formation of friction films were discussed. The results show that with the lubricant of Cu-coated graphite, the hardness, relative density, thermal conductivity, and interfacial bonding between the graphite and matrix can be greatly improved. Under the same test condition, the average friction coefficient, wear rate, and friction temperature of the specimen with added Cu-coated graphite are both lower than those of the specimen with added uncoated graphite. The two specimens show different variation trends in the instantaneous friction coefficient during the tests, and the variation of the instantaneous friction coefficient at a high initial test speed is also different from that at a low initial test speed for each specimen. The two specimens also show differences in the continuity of friction film and the content of graphite and oxide in the friction film.

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Tribological performance of self-lubricated polyamide6/boric oxide composites after water conditioning

Pigment & Resin Technology ◽

10.1108/prt-05-2021-0049 ◽

2021 ◽

Vol ahead-of-print (ahead-of-print) ◽

Cited By ~ 1

Author(s):

Kawaljit Singh Randhawa ◽

Ashwin Patel

Keyword(s):

Friction Coefficient ◽

Abrasion Resistance ◽

Tribological Performance ◽

Boric Oxide ◽

Resistance Testing ◽

Tribological Behaviour ◽

Content Type ◽

Wear Rates ◽

Water Conditioning ◽

Oxide Composites

Purpose This paper aims to investigate the tribological performance, i.e. abrasion resistance, friction coefficient and wear rates, of self-lubricated water conditioned polyamide6/boric oxide composites. Design/methodology/approach Polyamide6 and polyamide6/boric oxide self-lubricated composites were immersed in water for 15 days to analyze the effect of water conditioning on friction, wear and abrasion resistance. Tribological testing on pin-on-disc tribometer and abrasion resistance testing on TABER abrader were performed to see the friction coefficient and wear rates of materials. The scanning electron microscopy (SEM) characterizations were performed to analyze the wear tracks. Findings Tribological testing results revealed the loss in abrasive resistance, but there was an improvement in frictional coefficient and wear rates with steel after water absorption. The SEM images clearly show less depth of wear tracks in water-conditioned materials than dry ones. Water conditioning was found supportive in the formation of smooth lubricating transfer film on steel disc during the tribological testing. Originality/value The tribological behaviour of polymer composites is different in dry and in high humidity or water conditions. Experiments were performed to investigate B2O3 solid lubricant filler effectiveness on tribological behaviour of water-conditioned polyamide composites. Bonding between polyamide6 and water molecules plus the formation of orthoboric acid was found advantageous in decreasing the friction coefficient and wear rates of composites.

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Experimental study on friction coefficient and temperature rise of heavy-load grease-lubricated spherical plain bearings with surface texture

Industrial Lubrication and Tribology ◽

10.1108/ilt-08-2020-0293 ◽

2021 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Jinlong Shen ◽

Tong Zhang ◽

Jimin Xu ◽

Xiaojun LIU ◽

Kun Liu

Keyword(s):

Friction Coefficient ◽

Temperature Rise ◽

Surface Texture ◽

Tribological Performance ◽

Textured Surface ◽

Textured Surfaces ◽

Roughness Parameters ◽

Heavy Load ◽

Friction Coefficients ◽

Content Type

Purpose This paper aims to improve the tribological performance of grease-lubricated spherical plain bearings (SPBs) under heavy load, dimple-type textures were prepared by laser on the outer surface of the inner ring. The influence of roughness parameters of a textured surface on reducing friction coefficient and temperature rise was also explored. Design/methodology/approach This study adopts a laser processing method to fabricate dimple-type textures. Three-dimensional roughness parameters were used to characterize the textured surfaces. The friction coefficients of five SPBs with surface texture and one original commercially available SPB without surface texture under different nominal loads were measured on a self-established test rig. The data of temperature rise were obtained by nine embedded thermal couples. Findings The results indicate that SPBs with textures generally exhibit lower friction coefficients than the original SPB without textures. The dimple depth has a significant influence on improving the tribological performance, which coincides with the analysis by surface roughness parameters. A textured surface with negative Ssk and high Vvc has the minimum temperature rise. Originality/value As it is too difficult to arrange sensors into heavy-load SPBs, there are few reports about the temperature characteristics. Through nine embedded thermal couples, the distribution of temperature rise on the inner ring of SPBs was given in this study. The positive effect of surface texture on reducing temperature rise and friction coefficient was verified, which is beneficial for the design of heavy-load SPBs.

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Frictional Behaviour of Composite Anodized Layers on Aluminium Alloys

Materials ◽

10.3390/ma13173747 ◽

2020 ◽

Vol 13 (17) ◽

pp. 3747

Author(s):

Radomir Atraszkiewicz ◽

Marcin Makówka ◽

Łukasz Kołodziejczyk ◽

Bartłomiej Januszewicz ◽

Jan Sucharkiewicz

Keyword(s):

Friction Coefficient ◽

Wear Rate ◽

Tribological Properties ◽

Friction Coefficients ◽

Friction Forces ◽

Sic Nanoparticles ◽

Wear Rates ◽

Three Samples ◽

Micro Arc Oxidation ◽

Embedded Nanoparticles

Three variants of the micro arc oxidation (MAO) technique have been used to treat a 2017A alloy surface. The first variant was a pure anodized layer, the second an anodized layer with SiC embedded nanoparticles and the third an anodized layer with Si3N4 nanoparticles. Tribological tests were performed for all variants, on three samples for every case. Friction coefficients and wear rates were calculated on the basis of experiments. The pure anodized layer manifested friction coefficient values within the range of 0.48 ÷ 0.52 and a wear rate in the range ~10−15 m3N−1m−1. SiC nanoparticles improved the tribological properties of the layer, as indicated by a reduction of the friction coefficient values to the range of 0.20 ÷ 0.26 with preserved very high resistance against wear (wear rate ~10−15 m3N−1m−1). Si3N4 particles embedded in anodized layer deteriorated the tribological properties, with a reduction in the resistance against fatigue and wear, intensification of friction forces and a change in the nature of friction contact behavior to more abrasive-like nature (friction coefficients ranging from 0.4 to 0.6 and wear rates ~10−14 m3N−1m−1).

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Identification and modelling of applicable wear conditions for stir cast Al-composite

Friction ◽

10.1007/s40544-019-0302-6 ◽

2019 ◽

Vol 8 (5) ◽

pp. 847-873

Author(s):

Santanu Sardar ◽

Santanu Kumar Karmakar ◽

Debdulal Das

Keyword(s):

Orthogonal Design ◽

Optimization Technique ◽

Matrix Alloy ◽

Stir Casting ◽

Tribological Performance ◽

Friction Coefficients ◽

Wear Rates ◽

Control Factors ◽

Desirability Approach ◽

Abrasive Size

Abstract A comprehensive study of the tribological performance of the Al-Zn-Mg-Cu/Al2O3 composite and its matrix alloy is presented in this paper, with a specific emphasis to identify and model the applicable wear conditions where the composite provides a minimum of 50% reduction in wear rate and 25% lowering of the friction coefficient. Two-body abrasion experiments following Taguchi L27 orthogonal design have been performed separately on alloy and composite materials, both prepared by the stir casting method. The influence of crucial control factors including silicon carbide (SiC) abrasive size, load, sliding distance, and velocity on the percentage variations of wear rates and friction coefficients between alloy and composite have been studied using the analysis of variance technique and full quadratic regression method. The dominant control factors are identified as abrasive size, load, and the interaction between abrasive size and load. This has been verified by establishing the influence of abrasive size and load on variations of wear mechanisms like microcutting, microploughing, and delamination, identified by means of in-depth characterization of worn surfaces and generated debris for both alloy and composite. The selection of applicable tribological condition for the composite has been accomplished by adopting the multi-response optimization technique based on combined desirability approach to obtain concurrent optimization of the percentage variations of wear rates and friction coefficients. Predictive models correlating the superiority of tribological performance of composite with abrasion conditions have been developed, and these are found to be accurate (errors <10%), as determined by confirmatory experiment.

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Effect of nanoparticles on the tribo-layers and the tribology of a steel-on-steel couple

Proceedings of the Institution of Mechanical Engineers Part J Journal of Engineering Tribology ◽

10.1177/1350650118765005 ◽

2018 ◽

Vol 233 (1) ◽

pp. 30-40 ◽

Cited By ~ 4

Author(s):

Kangmin Chen ◽

Wei Jiang ◽

Xianghong Cui ◽

Shuqi Wang

Keyword(s):

Friction Coefficient ◽

Tribological Behavior ◽

Tribological Performance ◽

Wear Rates ◽

Cover Type ◽

Sliding Interface ◽

Aisi 1045 Steel ◽

Aisi 1045 ◽

1045 Steel ◽

Mixture Additives

The tribological behavior and tribo-layers of AISI 1045 steel sliding against 52100 steel were investigated in the case of supplying MoS2, Fe2O3, and their mixtures onto the sliding interface. When nanoparticles were supplied, tribo-layers were formed on the worn surfaces. The tribological behavior of the sliding pair depended on the characteristics of tribo-layers, which were decided by different nanoparticles. As the additives—especially the ones containing MoS2—were supplied onto the sliding interface, the wear rates and friction coefficients of both 1045 steel and 52100 steel were markedly decreased to extremely low values, approaching zero and marginally undulated with the increase in load. Single-component Fe2O3 nanoparticles markedly reduced the wear rate of 1045 steel with slightly increased friction coefficient, but its decreased extent was merely half of that of the additives containing MoS2. The improvement of the tribological performance of steels was attributed to the formation of protective tribo-layers. The addition of pure Fe2O3 resulted in the formation of insert-type tribo-layers, while cover-type tribo-layers were formed by the addition of the mixture additives of Fe2O3+MoS2 and pure MoS2. The cover-type tribo-layers provided more protective and lubricative functions than that of the insert-types.

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New Equation for Predicting Pipe Friction Coefficients Using the Statistical Based Entropy Concepts

Entropy ◽

10.3390/e23050611 ◽

2021 ◽

Vol 23 (5) ◽

pp. 611

Author(s):

Yeon-Woong Choe ◽

Sang-Bo Sim ◽

Yeon-Moon Choo

Keyword(s):

Friction Coefficient ◽

Accurate Determination ◽

Mean Velocity ◽

Friction Coefficients ◽

Flow Discharge ◽

Comparison Results ◽

Flow Loss ◽

Key Variables ◽

New Equation

In general, this new equation is significant for designing and operating a pipeline to predict flow discharge. In order to predict the flow discharge, accurate determination of the flow loss due to pipe friction is very important. However, existing pipe friction coefficient equations have difficulties in obtaining key variables or those only applicable to pipes with specific conditions. Thus, this study develops a new equation for predicting pipe friction coefficients using statistically based entropy concepts, which are currently being used in various fields. The parameters in the proposed equation can be easily obtained and are easy to estimate. Existing formulas for calculating pipe friction coefficient requires the friction head loss and Reynolds number. Unlike existing formulas, the proposed equation only requires pipe specifications, entropy value and average velocity. The developed equation can predict the friction coefficient by using the well-known entropy, the mean velocity and the pipe specifications. The comparison results with the Nikuradse’s experimental data show that the R2 and RMSE values were 0.998 and 0.000366 in smooth pipe, and 0.979 to 0.994 or 0.000399 to 0.000436 in rough pipe, and the discrepancy ratio analysis results show that the accuracy of both results in smooth and rough pipes is very close to zero. The proposed equation will enable the easier estimation of flow rates.

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Theoretical Studies of the Interaction between Screw Surface and Material in the Mixer

Materials ◽

10.3390/ma14040962 ◽

2021 ◽

Vol 14 (4) ◽

pp. 962

Author(s):

Andrzej Marczuk ◽

Vasily Sysuev ◽

Alexey Aleshkin ◽

Petr Savinykh ◽

Nikolay Turubanov ◽

...

Keyword(s):

Friction Coefficient ◽

High Efficiency ◽

Animal Feed ◽

Structural Features ◽

Power Demand ◽

Friction Coefficients ◽

Length Unit ◽

Mixing Chamber ◽

Size Of Particles ◽

The Impact

Mixing is one of the most commonly used processes in food, animal feed, chemical, cosmetic, etc., industries. It is supposed to provide high-quality homogenous, nutritious mixtures. To provide appropriate mixing of materials while maintaining the process high efficiency and low energy consumption it is crucial to explore and describe the material flow caused by the movement of mixing elements and the contact between particles. The process of mixing is also affected by structural features of the machine components and the mixing chamber, speed of mixing, and properties of the mixed materials, such as the size of particles, moisture, friction coefficients. Thus, modeling of the phenomena that accompany the process of mixing using the above-listed parameters is indispensable for appropriate implementation of the process. The paper provides theoretical power calculations that take into account the material speed change, the impact of the material friction coefficient on the screw steel surface and the impact of the friction coefficient on the material, taking into account the loading height of the mixing chamber and the chamber loading value. Dependencies between the mixer power and the product degree of fineness, rotational speed of screw friction coefficients, the number of windings per length unit, and width of the screw tape have been presented on the basis of a developed model. It has been found that power increases along with an increase in the value of these parameters. Verification of the theoretical model indicated consistence of the predicted power demand with the power demand determined in tests performed on a real object for values of the assumed, effective loading, which was 65–75%.

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Improvement of mechanical properties of HfB2-based composites by incorporating in situ SiC reinforcement through pressureless sintering

Scientific Reports ◽

10.1038/s41598-021-88566-0 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

S. Ghadami ◽

E. Taheri-Nassaj ◽

H. R. Baharvandi ◽

F. Ghadami

Keyword(s):

Mechanical Properties ◽

Thermal Conductivity ◽

Relative Density ◽

Pressureless Sintering ◽

Sintering Process ◽

Vacuum Atmosphere ◽

Sic Reinforcement ◽

Microstructural Studies ◽

Composite Samples

AbstractHfB2, Si, and activated carbon powders were selected to fabricate 0–30 vol% SiC reinforced HfB2-based composite. Pressureless sintering process was performed at 2050 °C for 4 h under a vacuum atmosphere. Microstructural studies revealed that in situ SiC reinforcement was formed and distributed in the composite according to the following reaction: Si + C = SiC. A maximum relative density of 98% was measured for the 20 vol% SiC containing HfB2 composite. Mechanical investigations showed that the hardness and the fracture toughness of these composites were increased and reached up to 21.2 GPa for HfB2-30 vol% SiC and 4.9 MPa.m1/2 for HfB2-20 vol% SiC, respectively. Results showed that alpha-SiC reinforcements were created jagged, irregular, and elongated in shape which were in situ formed between HfB2 grains and filled the porosities. Formation of alpha-SiC contributed to improving the relative density and mechanical properties of the composite samples. By increasing SiC content, an enhanced trend of thermal conductivity was observed as well as a reduced trend for electrical conductivity.

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The Influence of the Addition of Ti on the Mechanical Properties of W-S-Ti Coatings

Materials Science Forum ◽

10.4028/www.scientific.net/msf.514-516.687 ◽

2006 ◽

Vol 514-516 ◽

pp. 687-691 ◽

Cited By ~ 5

Author(s):

Manuel Evaristo ◽

Ana Nossa ◽

Albano Cavaleiro

Keyword(s):

Mechanical Properties ◽

Friction Coefficient ◽

Tribological Performance ◽

The Self ◽

Wear Coefficient ◽

Gradual Loss ◽

Order Of Magnitude ◽

Amorphous Structures ◽

Ti Content ◽

Ti Films

In this work, W-S-Ti films were deposited by r.f. magnetron sputtering, using simultaneously WS2 and Ti targets. The atomic percentage of Ti in the coating was varied from 0 at.% up to 28 at.%. No significant variations in the S/W ratio with the increase of Ti content were observed. The increasing Ti contents in the films led to a gradual loss of crystallinity. Coatings with contents greater than ≈ 16 at.% only presents a broad peak characteristic of amorphous structures. Alloying the films with Ti led to significant improvements in the hardness (from 0.3 to 8.9 GPa). Also, the adhesive critical load continuously grew with the increase of the Ti content in the films. The wear coefficient of the films dropped more than one order of magnitude with the increase of Ti content whereas the friction coefficient was kept fairly constant with just a small increase in relation to single W-S film. In conclusion, to have a good tribological performance, the addition of Ti to the films should be balanced in order that the increase of the mechanical properties does not lead to severe loss of the self-lubricant properties.

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MICROSTRUCTURE AND PROPERTIES OF SiC PARTICLES REINFORCED COPPER BASED ALLOY COMPOSITE

Modern Physics Letters B ◽

10.1142/s021798491341025x ◽

2013 ◽

Vol 27 (19) ◽

pp. 1341025 ◽

Cited By ~ 1

Author(s):

YU HONG ◽

XIAOLI CHEN ◽

WENFANG WANG ◽

YUCHENG WU

Keyword(s):

Mechanical Properties ◽

Thermal Conductivity ◽

Electrical Conductivity ◽

Relative Density ◽

Volume Fraction ◽

Copper Matrix ◽

Matrix Composites ◽

Wear Properties ◽

Sic Particles ◽

Copper Based Alloy

Copper-matrix composites reinforced with SiC particles are prepared by mechanical alloying. The microstructure characteristics, relative density, hardness, tensile strength, electrical conductivity, thermal conductivity and wear properties of the composites are investigated in this paper. The results indicate that the relative density, macro-hardness and mechanical properties of composites are improved by modifying the surface of SiC particles with Cu and Ni . The electrical conductivity and thermal conductivity of composites, however, are not obviously improved. For a given volume fraction of SiC , the Cu / SiC ( Ni ) has higher mechanical properties than Cu / SiC ( Cu ). The wear resistance of the composites are improved by the addition of SiC . The composites with optimized interface have lower wear rate.

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