Effect of solidification cooling rate on microstructure and tribology characteristics of Zn-4Si alloy

The main objective of this work was to modify the microstructure and enhance the tribological properties of a new Zn-4Si al-loy through a high solidification cooling rate(SCR).According to the results,by increasing the SCR from 2.0 to 59.5℃/s the average size of primary Si particles and that of the grains reduced from 76.1 and 3780μm to less than about 14.6 and 460μm,respectively.Augment-ing the SCR also enhanced the microstructural homogeneity,decreased the porosity content(by 50%),and increased the matrix hardness(by 36%).These microstructural changes enhanced the tribological behavior.For instance,under the applied pressure of 0.5 MPa,an in-crease in the SCR from 2.0 to 59.5℃/s decreased the wear rate and the average friction coefficient of the alloy by 57%and 23%,respect-ively.The wear mechanism was also changed from the severe delamination,adhesion,and abrasion in the slowly-cooled alloy to the mild tribolayer delamination/abrasion in the high-cooling-rate-solidified sample.

Effects of Additives on the Microstructure and Tribology Performance of Ta-12W Alloy Micro-Arc Oxidation Coating

Oxide ceramic coatings were fabricated on tantalum alloys by micro-arc oxidation (MAO) to improve their hardness and tribological properties. The MAO coatings were manufactured in a mixed silicatephosphate electrolyte containing NaF and/or EDTA (ethylene diamine tetraacetic acid). The surface morphology,cross-sectional view, chemical composition, hardness, and wear performance of the coatings were analysed. As revealed by the scanning electron microscopy, silica-rich nodules appear on the MAO coating obtained in the silicate-phosphate electrolyte, but the formation of nodules is inhibited with NaF and/or EDTA in the electrolyte.Also, they reduce the roughness and improve the compactness of the coatings, which are composed of Ta_(2)O_(5),(Ta, O), and TaO. A thick and hard coating is obtained in the NaF-containing electrolyte, and the tribology performance is effectively improved. With additives, the nodule structure is detached from the coating surface and dissolved in the electrolyte. By using NaF as an electrolyte additive, the abrasion performance of the MAO coating is enhanced by decreasing the nodule structure, increasing the size of micropores, and improving the coating hardness.

Characteristics of Magnetic Tribology on High Flux Pair of Magnetic Driving Mechanism

The rectangle-like pulsed magnetic field acted on the rubbing pair was presented through analyzing the exciting property in the reciprocating travel. The test of wear in NG-x tester shows that the wear between the electromagnetic core and down magnetic board distributes in the high velocity slip region of reciprocating travel, and the adhesive wear in the low velocity slip region nearby up and down dead points is depressed owing to the presence of high flux magnetic field. The lubrication by magnetic fluid with high permeability effectively reduces the friction and wear of high flux rubbing pair, and improves the conducting property of magnetic circuit constructed by the rubbing pair, which is beneficial to increase the operation performance of magnetic driving mechanism.

Reciprocating sliding tribology of brake oil treated carbon fiber reinforced ceramic matrix composites

The effect of brake oil on sliding behavior of carbon/carbon(C/C) and carbon/carbon-silicon carbide(C/C-SiC) composites was investigated with the variation of laminate orientation and surface conformity. The partial and low conformity contacts with the normal and parallel orientations of laminates were considered. The normal load was varied from 50 to 90 N in a step of 10 N. The friction and wear behavior was investigated under reciprocating sliding conditions. The results showed that friction coefficient and wear loss of composites with normal orientation of laminates were larger as compared to those of composites with parallel orientation of laminates. C/C composites with normal orientation of laminates yielded the highest value of friction coefficient. Wear loss decreased by a maximum of 78%, and friction coefficient decreased by a maximum of 49% in low conformity contacts as compared to partial conformity contacts. The presence of brake oil reduced the adhesion tendency of compacted wear debris because the formation of friction film was difficult, and thus, friction behavior was affected. The wear debris retention between the contact surfaces due to confined area motion in reciprocating sliding depicted the tribological behavior.

The influence of MoS_2 on tribology characteristic parameter of Ni60A/MoS_2 composite lubricating coating

The influence of MoS2 on the tribology characteristic parameter of Ni60A/MoS2 composite lubricating coating was researched on the UMT-2 fretting abrasion tester （USA） The result shows that with increasing content of MoS2, the hardness curve of the composite coating decreases and the trend accelerates. Under the same experimental conditions, the mass loss of plasma spray composite coating without adding MoS2 iS 1.27×10^-2 mg. When the amount of MoS2 reaches 35%, the mass loss is 0.96×10^-2 mg. It can be seen that adding MoS2 phase can improve the wear resistance, the amplitude of which is close to 30%. The friction coefficient of plasma spray composite coating without adding MoS2 is 0.23. Adding MoSz could decrease the friction coefficient of the coating and presents a downtrend. When the mass fraction is 35%, the friction coefficient is the smallest （0.13）, and the range is doubled.

Green Tribology： Influence of New DLC Coatings-Orientants and Amorphous on Antifriction Properties of Lubricants

Tribological properties of two new DLC--monocrystalline and amorphous nanostructural coating--are studied under conditions of boundary lubrication in inactive oil, as green tribology aspect. The friction tests were carried out by using two test configurations： ＂ball-on-disc＂ and ＂ring-to-ring＂. Friction surfaces were coated by carbon of two types： monocrystalline and amorphous ones. As lubricants some model and commercial oils were used. It is found that the friction coefficient and its temperature dependence differ significantly for carbon films under study. The obtained results were attributed to different orientating effect of these coatings on structural ordering in boundary layers, which structure is considered as a mesophase of liquid crystals. The findings suggest that the carbon coatings with orientating effect on boundary layers are advantageous for improving antifriction characteristics and for governing processes of boundary lubrication.

Coupling Analysis of Tribology and Dynamics in Rolling Interface

The metal plastic flow, tribology performance and work roll vibration on the rolling interface were analyzed. Considering the effect of work roll vibration on the tribology behavior of rolling interface, the damping of rolling interface was researched. It is found that the rolling interface, where the partial hydraulic lubricating film and dry friction area coexist, is of negative damping coefficient. The negative damping results from the dynamic variation of the thickness of lubricating film in the rolling interface, and is caused by the special coupling between dynamics and tribology of the rolling interface.

Investigation on the Tribology of Co Implanted Stainless Steel Using Metal Vapor Vacuum Arc Ion Source

AISI 304 stainless steel was ion implanted with Co, and the tribological property on the surface of the stainless steelwas investigated. The Co ion implantation was carried out using a metal vapor vacuum arc (Mevva) broad-beam ionsource with an extraction voltage of 40 kV, implantation doses of 3×10^(17)/cm^2 and 5×10^(17)/cm^2, and ion currentdensities of 13, 22 and 32μA/cm^2. The results showed that the near-surface hardness of Co-implanted stainless steelsample was increased by 50% or more, and it increased with increasing ion current density at first and then declined.The friction coefficient decreased from 0.74 to 0.20 after Co implantation. The wear rate after Co implantationreduced by 25% or more as compared to the unimplanted sample. The wear rate initially decreased with increasingion current density and then an increase was observed. Within the range of experimental parameters, there existsa critical ion current density for the Co-implanted stainless steel, at which the wear rate decreased with increasingretained dose, going through a minimum and then increased. The critical ion current density in this paper is about22μA/cm^2.

Surface Characterization and Tribology Behavior of PMMA Processed by Excimer Laser

Polyoxymethylene methacrylate (PMMA) is widely used in ophthalmic biomaterials. Misuse of PMMA in extreme environments is likely to damage the ocular surface and intraocular structures. The surface characterization and tribological behavior of PMMA processed using an excimer laser were investigated in this study by contrasting diferent lubrication conditions and friction cycles. The results show that the roughness of the material surface increases with laser processing, which changes its physical structure. Under lubrication, the laser-treated PMMA exhibits better hydrophilicity, especially during the use of eye drops. No obvious relationship exists between the laser-processing time and friction behavior. However, the laser treatment may contribute to the formation of friction and wear mechanisms of PMMA materials. Laser-treated PMMA in saline solution exhibits better abrasive resistance by showing a lower wear rate than that in eye drops, although it has a higher friction coefcient. In this study, the diferent friction stages in laser-treated PMMA were clarifed under two lubrication conditions. The wear rates of the laser-treated PMMA were found to decrease with the number of cycles, and the friction coefcient has a similar variation tendency. The wear behavior of the laser-treated PMMA is dominated by the main abrasive wear and secondary transferred flm formation. This study provides a theoretical basis for the development and application of ophthalmic biomaterials in complex environments by examining the material surface interface behavior and wear mechanism after laser processing using PMMA as the research matrix.

To the New Concept of Green Tribology

The aim of the present work is to confirm the fundamental possibility of creating new generation of the nanostructured composite coatings-orientants are studied under conditions of boundary lubrication in inactive oil, as green tribology aspect and to experimentally prove the efficacy of the nanostructured composite coatings-orientants for engineering applications. Tribological properties of nanostructured composite coatings-orientants are studied under conditions of boundary lubrication in inactive oil, as green tribology aspect. The friction tests were carried out by using two test configurations: “ball-on-disc” and “ring-to-ring”. As lubricants some model and commercial oils were used. It is found that the friction coefficient and its temperature dependence differ significantly for nanostructured composite coatings under study. The obtained results were attributed to different orientating effect of these coatings on structural ordering in boundary layers, which structure is considered as a mesophase of liquid crystals. The findings suggest that the nanostructured composite coatings-orientants with orientating effect on boundary layers are advantageous for improving antifriction characteristics and for governing processes of boundary lubrication. The nanostructured composite coatings-orientants can improve lubricating properties of oils (with and without additives) and may be advantageous for engineering practice as they improve antifriction characteristics of rubbing pairs and allow controlling the processes of boundary lubrication. Thus, received nanostructured composite coatings-orientants can be today the best materials of green tribology in engineering.

AlSi11/ Si₃N₄Interpenetrating Composites Tribology Properties of Aluminum Matris Composites

In present work, the metal-ceramic interpenetrating composites (IPCs) as AlSi11/ Si3N4 are fabricated by infiltrating technique. IPCs exhibit special characterization of brittle ceramic reinforced phase introduced by ductile metal matrix phase. During the sliding wear processes, IPCs exhibit four wear mechanism such as initial adhesive wear, mixed adhesive and abrasive wear, adhesive wear and final abrasive wear. Reinforcements inhibit plastic flow and restrict propagation of wear cracks. Increase in the volume fraction of reinforcement leads to improvement in the wear resistance. Under higher load and lower round speed conditions, the friction coefficients are lower than that of relative conditions.

Effect of hot rolling on microstructure and tribology behaviors of Ti-50.8Ni alloy

We link different microstructures to tribological behaviors of Ti-50.8 Ni(mole fraction, %) in reciprocating mode at room temperature(20 ℃). Hot-rolled alloys with B2 phase exhibit lower coefficient of friction and wear rate compared to the ones with B19?. Stress-induced martensitic transformation occurs during sliding. However, multi-pass hot rolling weakens the wear resistance. In this study, microstructures were characterized through electron backscatter diffraction and transmission electron microscopy(EBSD/TEM). From the concept of energy conservation, the effects of weak intensity of hot-rolled textures on the wear resistance are minimal. Based on the result that the alloy with a higher portion of coincidence site lattice boundaries shows lower martensitic start transformation temperature in the DSC curves than that with higher KAM values, the delay on B2-B19? transformation from {112}B2 twins outweighs dislocations. Moreover, widely distributed small-angle grain boundaries owing to dynamic recovery improve the wear resistance effectively compared to those that are well-recrystallized.

Structure and Tribology Property of Carbon Nitride Films Deposited by MW-ECR Plasma Enhanced Unbalanced Magnetron Sputtering

Carbon nitride films were deposited by a twinned microwave electron cyclotron resonance （ECR） plasma source enhanced unbalanced magnetron sputtering system. The results indicate that the structure of the films is sensitive to the nitrogen content. The increase in the nitrogen flow ratio leads to an increase in the sp3 content and an improvement of the tribological properties.

AI for tribology:Present and future

With remarkable learning capabilities and swift operational speeds,artificial intelligence(AI)can assist researchers in swiftly extracting valuable patterns,trends,and associations from subjective information.Tribological behaviors are characterized by dependence on systems,evolution with time,and multidisciplinary coupling.The friction process involves a variety of phenomena,including mechanics,thermology,electricity,optics,magnetics,and so on.Hence,tribological information possesses the distinct characteristics of being multidisciplinary,multilevel,and multiscale,so that the application of AI in tribology is highly extensive.To delineate the scope,classification,and recent trends of AI implementation in tribology,this review embarks on exploration of the tribology research domain.It comprehensively outlines the utilization of AI in basic theory of tribology,intelligent tribology,component tribology,extreme tribology,bio-tribology,green tribology,and other fields.Finally,considering the emergence of"tribo-informatics"as a novel interdisciplinary field,which combines tribology with informatics,this review elucidates the future directions and research framework of"AI for tribology".In this paper,tribo-system information is divided into 5 categories:input information(I),system intrinsic information(S),output information(O),tribological state information(Ts),and derived state information(Ds).Then,a fusion method among 5 types of tribo-system information and different AI technologies(regression,classification,clustering,and dimension reduction)has been proposed,which enables tribo-informatics methods to solve common problems such as tribological behavior state monitoring,behavior prediction,and system optimization.The purpose of this review is to offer a systematic comprehension of tribo-informatics and to inspire new research ideas of tribo-informatics.Ultimately,it aspires to enhance the efficiency of problem-solving in tribology.

Research progress on the characteristics of current-carrying tribology in electrical transmission

The electrical transmission between moving parts requires contact pairs such as rolling rings,sliding rings,connectors,etc.These functional contact pairs can be defined as current-carrying frictional pairs because they need to bear the transmission of current while enduring friction and wear.The rough current-carrying frictional pairs are typical contact surface withstands the load of force,heat,and electricity,resulting in the unique contact characteristics of the current-carrying pair.The research progress of current-carrying tribology has been reviewed in this paper.The correlation mechanism between tribological performance and current-carrying performance has been summarized.The composite and competitive relationship between mechanical damage and electrical damage has been discussed.Methods for evaluating the dynamic performance of current-carrying tribology has been proposed.The spatiotemporal non-uniformity of current-carrying frictional damage has been revealed.Future research trends are expected at the end.

A review of recent advances in tribology

The reach of tribology has expanded in diverse fields and tribology related research activities have seen immense growth during the last decade.This review takes stock of the recent advances in research pertaining to different aspects of tribology within the last 2 to 3 years.Different aspects of tribology that have been reviewed including lubrication,wear and surface engineering,biotribology,high tem perature tribology,and computational tribology.This review attempts to highlight recent research and also presents future outlook pertaining to these aspects.It may however be noted that there are limitations of this review.One of the most important of these is that tribology being a highly multidisciplinary field,the research results are widely spread across various disciplines and there can be omissions because of this.Secondly,the topics dealt with in the field of tribology include only some of the salient topics(such as lubrication,wear,surface engineering,biotribology,high tem perature tribology,and computational tribology)but there are many more aspects of tribology that have not been covered in this review.Despite these limitations it is hoped that such a review will bring the most recent salient research in focus and will be beneficial for the growing community of tribology researchers.

A review of advances in tribology in 2020–2021

Around 1,000 peer-reviewed papers were selected from 3,450 articles published during 2020–2021,and reviewed as the representative advances in tribology research worldwide.The survey highlights the development in lubrication,wear and surface engineering,biotribology,high temperature tribology,and computational tribology,providing a show window of the achievements of recent fundamental and application researches in the field of tribology.

Green tribology:Fundamentals and future development

As green tribology is a new field of tribology still in its infancy,understanding its fundamentals is essential for its further development.In this article,a brief historical retrospective on the emergence of green tribology is introduced first,and then the definition,objectives,and disciplinary features of green tribology are clarified.In particular,the technological connotations of green tribology are expounded comprehensively.Also,the developing directions of this new area are envisaged.These findings may contribute to laying the foundation of further advancement in green tribology.

Tribology in metal forming at elevated temperatures

The tribo-characteristics of metal forming at high temperatures have not yet been well understood due to the complex nature of thermal,microstructural,interaction,and process parameters.This is a review paper on the effects of temperature,coating,and lubrication to the tribological characteristics in hot forming as well as the tribometers for different metal forming processes at elevated temperatures mainly based on the experimental work.The tribological behaviors of oxides in hot forming,such as rolling and stamping,were reviewed and presented.Some commonly used surface coatings and lubricants in hot forming were given.Many types of tribometer were selected and presented and some of them provided a great potential to characterize friction and wear at elevated temperatures.Nevertheless,more testing conditions should be further investigated by developing new tribometers.Eventually,experimental results obtained from reliable tribometers could be used in theory and model developments for different forming processes and materials at high temperatures.The review also showed the great potential in further investigations and innovation in tribology.

Tribology of rotating band and gun barrel during engraving process under quasi-static and dynamic loading

The engraving process of a projectile rotating band is one of the most basic research aspects in interior ballistics,which has not been thoroughly understood thus far.An understanding of this process is of great importance from the viewpoints of optimal design,manufacturing,use,and maintenance of gun and projectile.In this paper,the interaction of copper and nylon rotating bands with a CrNiMo gun barrel during engraving was studied under quasi‐static and dynamic loading conditions.The quasi‐static engraving tests were performed on a CSS‐88500 electronic universal testing machine(EUTM)and a special gas‐gun‐based test rig was designed for dynamic impact engraving of the rotating bands.The mechanical behaviors of copper and nylon were investigated under strain rates of 10^(−3) s^(−1) and 2×10^(3) s^(−1) using an MTS 810 and a split Hopkinson pressure bar(SHPB),respectively.Morphologies of the worn surfaces and cross‐sectional microstructures were observed with scanning electron microscope(SEM)and optical microscope(OM).It was found that large deformation and severe friction occur during engraving.The surface layer is condensed and correlated with a hardness gradient along the depth from the top worn surface.The structure of the rotating band and gun bore,band material,and loading rate have great effects on band engraving.The flow stress‐strain of the copper strongly depends on the applied strain rate.It is suggested that strain rate and temperature play significant roles in the deformation mechanism of rotating bands.