Microstructure and wear mechanisms of OCTG chasers

The wear mechanism and tool life of four types of oil country tubular goods chasers are studied herein via metallographic microscopy,scanning electron microscopy,and energy dispersive spectroscopy.Results show that when the tool has a fine and uniform microstructure,the main failure mode is wear failure.Furthermore,observed phenomena including large chip bonding,coating peeling,cracks demonstrate that the main wear mechanisms of the tool are adhesive wear,abrasive wear,coating flaking,and microchipping.

A Review on Fretting Wear Mechanisms,Models and Numerical Analyses

Fretting wear is a material damage in contact surfaces due to micro relative displacement between them.It causes some general problems in industrial applications,such as loosening of fasteners or sticking in components supposed to move relative to each other.Fretting wear is a complicated problem involving material properties of tribosystem and working conditions of them.Due to these various factors,researchers have studied the process of fretting wear by experiments and numerical modelling methods.This paper reviews recent literature on the numerical modelling method of fretting wear.After a briefly introduction on the mechanism of fretting wear,numerical models,which are critical issues for fretting wear modelling,are reviewed.The paper is concluded by highlighting possible research topics for future work.

Abrasive Wear Mechanisms of Sand Particles Intruding into ATM Roller-scraper Tribosystem

The roller-scraper tribosystem of automatic teller machine（ATM） plays an important role in reliable cash requests.However,the abrasive wear of the polymer tribosystem becomes a prominent problem when operating in sandy environment.The wear behavior of the tribosystem in a simulated sandy environment has been experimentally studied previously.However the abrasive wear mechanism of roller-scraper tribosystems is still unknown to new design.The wear rates of polymer rollers were examined comprehensively and several jumping variations were found in the full data extent.Three wear stages were classified by the magnitude of wear rates,and different dominant wear mechanisms corresponding with different particle diameter were found by examining the worn surfaces.Accordingly a presumption was proposed that wear mechanisms in different stages were correlated with sand particles of different diameter.In a verification experiment,three typical wear mechanisms including cutting,ploughing,and wedging were found corresponding with different wear stages by scanning electron microscope（SEM） examination.A theoretical analysis was carried out with a simplified sphere particle intrusion model and the transfer conditions for different wear mechanisms were studied referring to the slip-field theory.As a main result,three typical wear models versus friction coefficient of particle/roller,and particle radius were mapped with variant hardness of the polymer roller and ratio of contact shear stress to bulk shear stress.The result illuminated the abrasive wear mechanism during particle intrusion.Particularly,the critical transition conditions gave the basis for improving the wear performance of roller-scraper tribosystems in a sandy environment.

High-temperature wear mechanisms of TiNbWN films:Role of nanocrystalline oxides formation

Réfractory high/medium entropy nitrides(HENs/MENs)exhibit comprehensive application prospects as protective films on mechanical parts,particularly those subjected to sliding contacts at elevated temperatures.In this study,a new MEN system TiNbWN,forming a single fc solution,is designed and its wear performance at temperatures ranging from 25 to 750℃is explored.The wear mechanisms can be rationalized by examining the subsurface microstructural evolutions using the transmission electron microscopy as well as calculating the phase diagrams and interfacial adhesion behavior employing calculation of phase diagram(CALPHAD)and density functional theory(DFT).To be specific,increased wear losses occur in a temperature range of 25-600℃,being predominantly caused by the thermally-induced hardness degradation;whereas at the ultimate temperature(750℃),the wear loss is refrained due to the formation of nanocrystalline oxides(WnO_(3n-2r)TiO_(2),and TiOx),as synergistically revealed by microscopy and CALPHAD,which not only enhance the mechanical properties of the pristine nitride film,but also act as solid lubricants,reducing the interfacial adhesion.Thus,our work delineates the role of the in situ formed nanocrystalline oxides in the wear mechanism transition of TiNbWN thin films,which could shed light on the high-temperature wear behavior of refractory HEN/MENfilms.

Effect of Ni content on the wear behavior of Al-Si-Cu-Mg-Ni/SiC particles composites

In recent years,the addition of Ni has been widely acknowledged to be capable of enhancing the mechanical properties of Al-Si alloys.However,the effect of Ni on the wear behaviors of Al-Si alloys and Al matrix composites,particularly at elevated temperat-ures,remains an understudied area.In this study,Al-Si-Cu-Mg-Ni/20wt%SiC particles(SiCp)composites with varying Ni contents were prepared by using a semisolid stir casting method.The effect of Ni content on the dry sliding wear behavior of the prepared compos-ites was investigated through sliding tests at 25 and 350℃.Results indicated that theθ-Al_(2)Cu phase gradually diminished and eventually disappeared as the Ni content increased from 0wt%to 3wt%.This change was accompanied by the formation and increase inδ-Al_(3)CuNi andε-Al_(3)Ni phases in microstructures.The hardness and ultimate tensile strength of the as-cast composites improved,and the wear rates of the composites decreased from 5.29×10^(−4)to 1.94×10^(−4)mm^(3)/(N∙m)at 25℃and from 20.2×10^(−4)to 7×10^(−4)mm^(3)/(N∙m)at 350℃with the increase in Ni content from 0wt%to 2wt%.The enhancement in performance was due to the presence of strengthening network structures and additional Ni-containing phases in the composites.However,the wear rate of the 3Ni composite was approximately two times higher than that of the 2Ni composite due to the fracture and debonding of theε-Al_(3)Ni phase.Abrasive wear,delamination wear,and oxidation wear were the predominant wear mechanisms of the investigated composites at 25℃,whereas delamination wear and oxid-ation wear were dominant during sliding at 350℃.

Wear mechanisms and hardness thresholds under repeated impact contact loading

Experiments were performed on 20 different types of materials to analyze the impact contact wear and to establish the wear mechanism map. The wear mechanism has been categorized into three prominent regions(delamination wear, quasi-nano wear and lamination-like wear) and is governed by two hardness thresholds(H_(dq) and H_(ql)). When the material hardness Hcp<H_(dq), the delamination wear is the dominant wear mechanism; when H_(cp)>H_(ql), the mechanism is lamination-like wear; however, when H_(cp) is between Hdq and H_(ql), the mechanism is determined to be quasi-nano wear. H_(dq) is determined to be the threshold hardness between delamination wear and quasi-nano wear that reflects the cracks being produced in the subsurface layer, whereas, H_(ql) is termed threshold hardness between quasi-nano wear and lamination-like wear with formation of nanostructure within the surface layer.

Corrosion and wear properties of in situ(TiB+TiC)/TA15 composites with a high volume percentage of reinforcement

The in situ(TiC+TiB)/TA15 composites with different volume percentages of reinforcement(10%,15%,20%and 25%)were prepared by water-cooled copper crucible vacuum suspension melting technology.The structures and compositions of the TA15 alloy and its composites were analyzed by XRD and EDS,and their electrochemical corrosion behaviors in the 3.5%NaCl solution were studied.Corrosion wear testing was conducted using a reciprocating ball-on-disc wear tester under a 10 N load.Results show that the in situ fibrous TiB phase and the granular TiC phase are uniformly distributed on the composite matrix.The microhardness can reach up to 531 HV as 25vol.%TiC+TiB reinforcement is added.Compared with the TA15 alloy,the volume wear rate decreases from(2.21±0.07)×10^(-4)to(1.75±0.07)×10^(-4)mm^(3)·N^(-1)·m^(-1)by adding 15vol.%TiC+TiB reinforcement,and the wear mechanism is adhesive wear.When the volume percentage of the reinforcement phase reaches 25%,the volume wear rate increases from(1.75±0.07)×10^(-4)to(2.41±0.07)×10^(-4)mm^(3)·N^(-1)·m^(-1),and the wear mechanism changes into abrasive wear.The volume loss resulted by the interaction between corrosion and wear accounts for more than 27%of the total wear volume.The volume loss due to wear-induced corrosion changes from 1.94%to 4.06%with different additions of reinforcement.The volume loss caused by corrosion-induced wear initially increases from 24.08%to 26.90%as the reinforcement increases from 0 to 15%due to the increase of corrosion potential,and then decreases from 26.90%to 25.68%as the reinforcement increases from 15%to 25%due to the peeling of TiC phase.

Wear Performance of Laser Surface Hardened GCr15 Steel

In order to assess the new tribological properties of laser surface hardened GCr15 steel, the wear resistance between specimens treated with laser and those of conventionally hardened under dry sliding conditions was compared. The change of wear mechanisms in laser hardened GCr15 resulted in a distinct difference in wear rates. The results showed that quenched zones not only had sufficient depth of hardening and higher hardness, but had more retained austenite and finer carbides because of a higher degree of carbide dissolution. Laser surface hardened GCr15 steel specimens exhibited superior wear resistance to their conventionally hardened specimens due to the effects of the microstructure hardening, high hardness and toughness. The wear mechanism for both the laser quenched layer and conventionally hardened layer was highly similar, generally involving adhesive, material transfer, wear-induced oxidation and plowing. When conventionally hardened block specimens rubbed against the laser hardened specimens, the surface of conventionally hardened block specimens was polished. The microstructural thermal stability was increased after laser surface treatment.

Investigation on dry sliding wear behavior of Mg/BN nanocomposites

The present research objective is to investigate the effect of boron nitride nanoparticles reinforcement on dry sliding wear behavior of pure Magnesium and magnesium nanocomposites.The fabricated nanocomposites contains varied percentages of boron nitride such as 0%(pure Mg),0.5%,1.5%and 2.5%were synthesized by using powder metallurgy technique and followed by a hot working process called hot extrusion.The pin on disk equipment was used for conducting the wear tests for traditional loads of 5 N,7 N and 10 N at different sliding speeds of 0.6,0.9 and 1.2 m/s against the steel disk at room temperature.For all traditional loads and sliding speeds,the changes in wear rate and friction co-efficient(μ)with respect to sliding distances were observed and analyzed.The wear characteristics are observed with the help of scanning electron microscopy under given test conditions.To investigate dominant wear mechanisms for various test conditions,the morphologies of all worn composites surfaces were analyzed.Final results show that,for all nanocomposites the wear level raises with respect to the sliding speeds and loads.Magnesium reinforced with 0.5%boron nitride shows lower wear rates and low friction coefficient values compare with magnesium reinforced with 1.5%boron nitride and 2.5%boron nitride nanocomposites.

Friction and Wear Behaviors of MoS_2/Zr Coated HSS in Sliding Wear and in Drilling Processes

MoS2 metal composite coatings have been successful used in dry turning, but its suitability for dry drilling has not been yet established. Therefore, it is necessary to study the friction and wear behaviors of MoS2/Zr coated HSS in sliding wear and in drilling processes. In the present study, MoS2/Zr composite coatings are deposited on the surface of W6Mo5Cr4V2 high speed steel（HSS）. Microstructural and fundamental properties of these coatings are examined. Ball-on-disc sliding wear tests on the coated discs are carried out, and the drilling performance of the coated drills is tested. Test results show that the MoS2/Zr composite coatings exhibit decreases friction coefficient to that of the uncoated HSS in sliding wear tests. Energy dispersive X-ray（EDX） analysis on the wear surface indicates that there is a transfer layer formed on the counterpart ball during sliding wear processes, which contributes to the decreasing of the friction coefficient between the sliding couple. Drilling tests indicate that the MoS2/Zr coated drills show better cutting performance compared to the uncoated HSS drills, coating delamination and abrasive are found to be the main flank and rake wear mode of the coated drills. The proposed research founds the base of the application of MoS2 metal composite coatings on dry drilling.

Effect of reinforcement content on the adhesive wear behavior of Cu10Sn5Ni/Si3N4 composites produced by stir casting

The main objective of this paper was to fabricate CuSnNi alloy and its composites reinforced with various contents of SiNparticles(5wt%, 10wt%, and 15wt%) and to investigate their dry sliding wear behavior using a pin-on-disk tribometer. Microstructural examinations of the specimens revealed a uniform dispersion of SiNparticles in the copper matrix. Wear experiments were performed for all combinations of parameters, such as load(10, 20, and 30 N), sliding distance(500, 1000, and 1500 m), and sliding velocity(1, 2, and 3 m/s), for the alloy and the composites. The results revealed that wear rate increased with increasing load and increasing sliding distance, whereas the wear rate decreased and then increased with increasing sliding velocity. The primary wear mechanism encountered at low loads was mild adhesive wear, whereas that at high loads was severe delamination wear. An oxide layer was formed at low velocities, whereas a combination of shear and plastic deformation occurred at high velocities. The mechanism at short sliding distances was ploughing action of SiNparticles, which act as protrusions; by contrast, at long sliding distances, direct metal–metal contact occurred. Among the investigated samples, the Cu/10wt% SiNcomposite exhibited the best wear resistance at a load of 10 N, a velocity of 2 m/s, and a sliding distance of 500 m.

Study on Dry Friction and Wear Properties of TiAl Alloy

A Ti-50Al alloy has been prepared by vacuum pressure casting.The full lamellar microstructure (FL) has been formed upon heat treating at 1400 ℃ and then furnace cooling.The frictional wear behavior of the alloy at the room temperature has been tested and its wear mechanism has been studied.The results show that with the increase of the load and sliding speed,the wear rate of the as-cast Ti-50Al alloy rises and the friction coefficient declines.When sliding speed is lower than 1.0 m/s the wear rate of the FL Ti-50Al alloy increased with the load and sliding speed,but the friction coefficient is relatively invariable at about 0.5.The wear mechanism is mainly of abrasive wear and adhesive wear.When sliding speed is higher than 1.5 m/s,the wear mechanism has changed to mainly oxidization wear so that the wear rate of the FL Ti-50Al alloy declines significantly and the friction coefficient increases.Compared to the as-cast alloy,the FL Ti-50Al alloy has better wear resistance.

Electrical Sliding Wear Properties of Mo-Reinforced MoS_2/Cu Composites

An adequate hardness of MoS2/Cu composites has not been achieved if these materials are applied under the extreme wear conditions. Therefore, Me-reinforced MoS2/Cu composites were prepared by powder metallurgy （P/M） methods. The electrical sliding wear properties in the absence or presence of Mereinforced MoS2/Cu composites were tested by HST-100 high speed electric-tribometer. The hardness, electrical conductivity, density, and microstmcture of MoS2/Cu composites were observed. Me-reinforcement MoS2/Cu composites are of good electrical conductivity, while the hardness of Mo-reinforcedment MoS2/Cu composites is about 33.3% higher than that of MoS2/Cu composites. With the addition of Me, composites show better wear properties under high speed and large electric current due to the improvement of hardness. The effects of current intensity and sliding velocity on the wear properties of the tested materials are complicated, and the wear mechanisms of MoS2/Cu composites are mainly abrasive wear and adhesive wear with arc erosion.

Analysis on the Wear Performances of Cemented Carbide Tools Containing Ti in the Coatings When Machining Ti⁃6Al⁃4V Alloys

Because of the high affinity of the same element Ti,cemented carbide tools containing Ti seem to be non⁃optimal in machining titanium alloys.However,in practice,cemented carbide tools containing Ti are still widely used in machining titanium alloys.Cutting experiments were conducted in order to systematically explain the contradictions between the practice and theory.The diffusion process between titanium alloys and the cemented carbide tools was analyzed by auger electron spectroscopy detecting the cutting regions.It was also analyzed by Ti/Co diffusion behavior simulated by molecular thermodynamics.The experimental results and the simulation results showed that the mutual diffusion of Ti/Co atoms was the major reason for the diffusion wear.The dissolution⁃diffusion wear was one of the main wear mechanisms for the cemented carbide tools containing Ti in the coatings.Moreover,four types of cemented carbide tools and two other types of cermet tools were used to machine the Ti⁃6Al⁃4V alloys at different cutting speeds to further verify the high affinity of cutting tools containing Ti in the substrate/coating.The verification experiments results showed that the cemented carbide tools containing Ti generally cannot be used for machining titanium alloys,but could show less affinity in the cutting regions with reasonable cutting conditions.

Experimental Study on Wear and Spalling Behaviors of Railway Wheel

The current researches of the wear and spalling behaviors of wheel/rail materials focus on the field investigation rather than the mechanism. However, it is necessary and significant for clarifying the mechanism and relationship between the wear and spalling damage of railway wheel to test and reproduce the wheel damages in laboratory. The objective of this paper is to investigate the wear and spalling damage behaviors of railway wheel using a JD-1 wheel/rail simulation facility, which consists of a small wheel serving as rolling stock wheel, and a larger wheel serving as rail. The damage process of wheel roller is explored in terms of the creep ratio, axle load, and carbon content by means of various microscopic examinations. The experimental results show that the wear volume growth of wheel roller is proved to be proportional to the increase of the creep ratio and normal load between simulating wheel and rail. The increase of carbon content of wheel material causes a linear reduction in the wear volume. The microscopic examinations indicate that the rolling wear mechanism transfers from abrasive wear to adhesive and fatigue wear with an increase of tangential friction force, which results in the initiation of fatigue crack, and then aggravates spalling damage on the wheel roller surface. The surface hardness of material depends strongly upon its carbon content. The decrease of the carbon content of wheel material may alleviate spalling damage, but can cause a significant growth in the wear volume of wheel roller. Therefore, there is a competitive relationship between the wear and spalling damage of wheel material. This research proposes an important measure for alleviating or preventing the wear and spalling damage of railway wheel material.

Dry sliding wear behavior of an extruded Mg-Dy-Zn alloy with long period stacking ordered phase

The dry sliding wear behavior of extruded Mg-2Dy-0.5Zn alloy(at.%)was investigated using a pin-on-disk configuration.The friction coefficient and wear rate were measured within a load range 20-760 N at a sliding velocity of 0.785 m/s.Microstructure and wear surface of alloy were examined using scanning electron microscopy.The mechanical properties of alloy were tested at room and elevated temperatures.Five wear mechanisms,namely abrasion,oxidation,delamination,thermal softening and melting dominated the whole wear behavior with increasing applied load.The extruded Mg-2Dy-0.5Zn alloy exhibited the better wear resistance as compared with as-cast Mg_(97)Zn_(1)Y_(2) alloy under the given conditions through contact surface temperature analysis.The improved wear resistance was mainly related to fine grain size,good thermal stability of long period stacking order(LPSO)phase and excellent higher-temperature mechanical properties.

Intelligent Identification of Wear Mechanism via On-line Ferrograph Images

Condition based maintenance（CBM） issues a new challenge of real-time monitoring for machine health maintenance. Wear state monitoring becomes the bottle-neck of CBM due to the lack of on-line information acquiring means. The wear mechanism judgment with characteristic wear debris has been widely adopted in off-line wear analysis; however, on-line wear mechanism characterization remains a big problem. In this paper, the wear mechanism identification via on-line ferrograph images is studied. To obtain isolated wear debris in an on-line ferrograph image, the deposition mechanism of wear debris in on-line ferrograph sensor is studied. The study result shows wear debris chain is the main morphology due to local magnetic field around the deposited wear debris. Accordingly, an improved sampling route for on-line wear debris deposition is designed with focus on the self-adjustment deposition time. As a result, isolated wear debris can be obtained in an on-line image, which facilitates the feature extraction of characteristic wear debris. By referring to the knowledge of analytical ferrograph, four dimensionless morphological features, including equivalent dimension, length-width ratio, shape factor, and contour fractal dimension of characteristic wear debris are extracted for distinguishing four typical wear mechanisms including normal, cutting, fatigue, and severe sliding wear. Furthermore, a feed-forward neural network is adopted to construct an automatic wear mechanism identification model. By training with the samples from analytical ferrograph, the model might identify some typical characteristic wear debris in an on-line ferrograph image. This paper performs a meaningful exploratory for on-line wear mechanism analysis, and the obtained results will provide a feasible way for on-line wear state monitoring.

Experimental study ofcasing wear under impact-sliding conditions

Theoretical analysis and field monitoring show that lateral vibration has very important effect on casing wear in deep & ultra-deep well drilling. The wear mechanism of casing under impact-sliding work conditions has been investigated and many experiments have been completed with a newly developed full-scale casing wear test machine. Test results present that adhesion wear, contact fatigue, and grinding abrasion are the main wear mechanisms under impact-sliding test conditions. The friction coefficient and linear wear rate of the casing rise obviously with an increase in impact load. And the larger the impact load, the rougher the worn surface of the casing. The linear wear rate decreased slightly but the average friction coefficient increased slightly with an increase in impact frequency under an impact load of 2,500 N. Both the linear wear rate of the casing and the average friction coefficient increased substantially with an increase in impact frequency under an impact load of 4,000 N. Under lower impact load conditions, grinding abrasion and contact fatigue are the main mechanisms of casing wear; under higher impact load conditions, adhesion wear and contact fatigue are the main mechanisms of casing wear.

Effect of large load on the wear and corrosion behavior of high-strength EH47 hull steel in 3.5wt%NaCl solution with sand

To simulate the wear and corrosion behavior of high-strength EH47 hull steel in a complicated marine environment in which seawater,sea ice,and sea sand coexist,accelerated wear and corrosion tests were performed in a laboratory setting using a tribometer.The effect of large loads on the behavior of abrasion and corrosion in a 3.5wt%NaCl solution with ice and sand to simulate a marine environment were investigated.The experimental results showed that the coefficient of friction(COF)decreases with increasing working load;meanwhile,the loading force and sand on the disk strongly influence the COF.The mechanisms of friction and the coupling effect of abrasion and corrosion in the 3.5wt%NaCl solution with sand were the wear and corrosion mechanisms;furthermore,the wear mechanism exerted the predominant effect.

Erosive Wear and Wear Mechanism of in situ TiC_P/Fe Composites

The base structure of in situ TiCp/Fe composites fabricated under industrial condition was changed by different heat treatments. Erosive wear tests were carried out and the results were compared with that of wear-resistant white cast iron. The results suggest that the wear resistance of the in situ TiCp/Fe composite is higher than that of wear-resistant white cast iron under the sand erosive wear condition. The wear mechanism of the wear-resistant white cast iron was a cycle process that base surface was worn and carbides were exposed, then carbides was broken and wear pits appeared. While the wear mechanism of in situ TiCp/Fe composite was a cycle process that base surface was worn and TiC grains were exposed and dropped. The wear resistance of in situ TiCp/Fe composite was lower than that of wear-resistant white cast iron under the slurry erosive wear condition. Under such circumstance, the material was not only undergone erosive wear but also electrochemistry erosion due to the contact with water in the medium. The wear behaviours can be a combination of two kinds of wear and the sand erosive wear is worse than slurry erosive wear.