Morphology Of Wear Debris Research Articles

MORPHOLOGY OF WEAR DEBRIS DURING DRY SLIDING OF Ti6Al4V/TiC COMPOSITE AT ELEVATED TEMPERATURES IN VACUUM CONDITIONS

A high temperature-dependent wear setup was employed to examine the Ti-6Al-4V (an [Formula: see text] titanium alloy) tribological properties under vacuum environments. The components of Ti-6Al-4V alloys used in aerospace and space environments are subjected to relative motion which results in the occurrence of tribo phenomenon. In this study, Ti6Al4V pin slid against SS316L disc under vacuum conditions at high temperature. The analysis of the wear debris clearly shows the effect of wear morphology of the worn surface which was analyzed by Field emission scanning electron microscope (FE-SEM) equipped with Energy-Dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The fine particles were observed at room temperature under vacuum conditions where Adiabatic Shear Band (ASB)-effects of plastic deformations and Mechanically Mixed Layer (MML) are observed at 137.3 N and 0.01[Formula: see text]ms[Formula: see text]. The tribological tests were carried out employing a pin on disc configurations at high temperatures (up to 400∘C). Further, its influence on wear debris under (137.3 N) high load and 0.01[Formula: see text]ms[Formula: see text] was also tested. The experimental results showed that various types of debris exhibited decreasing wear rates with increases in temperatures.

The evaluation of wear processes of the rolling-sliding contact by means of flake wear debris in dry and wet contact

One of the tasks of this paper is to explain the cause-and-effect relationship of the influence of operating parameters on the wear of the wheel-rail system where fatigue processes are initiated. In this way, learning about and defining the nature of the phenomenon, makes it possible to determine the reliability of component operation. The aim of this study was to determine the influence of operational parameters on tribological properties of the rolling-rail contact representing the wheel-rail association in real operating conditions. Determining the form of wear on the basis of laboratory tests carried out on an Amsler-type wear testing machine in the wheel-roller system makes it possible to determine the nature of changes occurring as a result of cyclic interaction of normal and tangential forces on the surface of the tested material, without the need for long-term and costly observation of the tested object in normal operation. Quantitative metallographic analysis of the morphology of wear debris was used to determine the intensity of surface wear. Determination of the influence of operational parameters on the stereological characteristics of wear debris makes it possible to predict the regenerative grinding of rails in service in the track and allows practical application by the sections of operation and diagnosis of the railway system.

Study on wear debris characteristics of different polyethylene under reciprocating sliding and compound motion modes

The UHMWPE wear debris has become an important reason affecting the service life and clinical reliability of the prosthesis. In order to further reveal the wear debris characteristics, three kinds of UHMWPE materials including non-crosslinked UHMWPE (UPE), Crosslinked UHMWPE (XLPE) and E-vitamin doped UHMWPE (EXPE) were taken as research objects, and the quantity, size, morphology and distribution characteristics of wear debris under reciprocating sliding and compound motion modes were systematically studied. Among them, the ball-on-disk samples were adopted under reciprocating sliding, and the real ball-on-socket contact mode of artificial cervical disc prosthesis was adopted under compound motion. The tribological experiments were performed with the frequency of 2Hz under 50,000 cycles with newborn bovine serum solution. The results showed that the dominant wear mechanism was abrasive wear accompanied by fatigue cracks under reciprocating sliding mode, while adhesive wear accompanied by a few abrasive wear under compound motion mode. Compared with the quantity of wear debris under reciprocating sliding mode, the number of UHMWPE debris under composite motion mode was reduced by 28.8%, 31.4% and 37.1% for UPE, XLPE and EXPE debris, respectively. The debris results of the three different polymers were consistent in the quantity, size range, morphology and distribution, but different in the size distribution characteristics. The largest proportion of EXPE debris size occurred in the range of less than 1 μm, while the largest proportion of UPE and XLPE debris size ranges from 1 to 5 μm under reciprocating sliding mode. When the debris size was in the range of 1–5 μm under compound motion mode, it accounted for the largest proportion with a value of 55.7%, 66.7% and 74.0% for UPE, XLPE and EXPE debris, respectively. The UHMWPE debris morphology included six main types: spherical, flakes, rods, fibrillar, granular, and other types. Granular and “other types” debris were the dominant types and the sum proportion of these two types of debris for the three kinds of UHMWPE materials was all as high as 80%. Hence, the material type, pair shape, load and movement profiles may have more or less influence on the quantity, size, morphology and distribution characteristics of UHMWPE debris.

Tribological behavior of Cr/a-C multilayered coating against PEEK under dry sliding condition

PEEK is of increasing interest as self-lubricating material for high temperature applications due to its remarkable mechanical properties. However, PEEK is apt to be worn out under dry sliding condition. In this work, the amorphous carbon(a-C) coating interleaved with Cr layer was deposited by a DC magnetron sputtering technique. The friction behavior of the Cr/a-C multilayered coating against PEEK pair was performed in dry atmosphere using a pin-on-disk tribometer. The tribochemical reactions was discussed in terms of evolution of surface morphology and chemical composition of wear debris. Results showed that the tribological behavior of Cr/a-C coating against PEEK pair is dominated by a synergistic effect arisen from inherent graphitization of a-C layer and suppressed adhesive reaction of transferred Cr layer.

Influence of Load and Speed on Tribological Performance of A390 and A515 Alloys in Dry Sliding Behavior A Comparative Study

In this study, tribological characteristics and wear debris morphology of A390 and A515 alloys are evaluated and compared. Components with a high wear resistance slide are typically made with alloys are A390 and A515, while components with high hardness requirements are usually made up with SS410. Those alloys were used in brake pads, and SS410 steel is used for the brake disc. Speed and pad force are the two factors that affect tribological characteristics such as friction coefficient and wear rate. Wear debris and wear track were examined by scanning election microscopy and optical microscope, respectively. The effect of sliding speed variations on wear and friction coefficient at various load conditions was also evaluated, and a comparative analysis was reported based on wear rates, coefficient of friction, and debris morphology for both materials. The A515 alloys shows higher friction coefficient under all the process conditions except at very low loads and high speeds due to increased superficial hardness and the composition of the case layer (oxygen-diffused/oxide formed).

Separation and Extraction of Mixed Grinding Chips of Artificial Joints with Different Densities by Multiple Centrifugal Separations

Aseptic loosening caused by the wear and tear of the artificial joint prosthesis after implantation is one of the main causes of artificial joint failure. Therefore, it is important to investigate the wear debris generated due to wear when developing new artificial joint materials. Aseptic loosening is related to the size, number, and morphology of wear debris, and this study proposed the separation and extraction of mixed wear debris with different density ratios of artificial joints by centrifugation to study the characteristics of different artificial joint wear and wear debris extraction rates. The results showed that multiple centrifugations to separate the mixed wear debris were able to reintroduce the wear debris on the wall of the centrifuge tube into the solution and that the wear debris extraction rate was increased. Suspensions with different density ratios of artificially jointed mixed wear debris were effectively separated by this method. The total extraction rate of the three repeated extractions compared to the first extraction rate, the extraction rate of CoCrMo wear debris increased by 6.7%, ultra-high molecular weight polyethylene (UHMWPE) wear debris increased by 15.1–23.44%, ZrO2 wear debris increased by 10.91%, and that of polyether ether ketone (PEEK) wear debris increased by 9.95%. This method for separating and extracting wear debris from artificial joints can realize the separation of mixed wear debris from artificial joints and obtain a high extraction rate and high-quality wear debris images, investigate the wear mechanism of artificial joint implants, and provide valuable information on the wear performance of new artificial joint implants under investigation.

Mechanical chemical polishing of large-size single-crystal diamond substrates with a sol-gel polishing tool

To process large-size single-crystal diamond (SCD) substrates efficiently, we proposed a method that utilises mechanical action to induce a chemical reaction for SCD polishing. In this study, a novel semi-fixed abrasive polishing tool suitable for high-speed polishing was fabricated using the sol-gel technique. A single-diamond abrasive and a mixed abrasive of diamond and CuO were selected for the SCD (100) plane polishing. After polishing for 2.5 h, the surface roughness of the SCD was reduced from approximately Ra 80 nm to approximately Ra 9 nm. The material removal rate (MRR) was measured quantitatively, and it was found that the mixed abrasive polishing performance was superior. In addition, the amorphous carbon content on SCD surface/subsurface after mixed abrasive polishing was significantly lower than single-diamond abrasive diamond abrasive. These results indicate that the scratching of the SCD surface by diamond abrasives induced the transformation of the carbon into amorphous carbon, which could then react with CuO powder. The wear debris morphology indicates that the surface material of the SCD was peeled off with a slice shape during single-diamond abrasive polishing, while it was removed with a slag-shape by the chemical reaction and slightly crushed during the mixed abrasive polishing. The material removal process for the mixed abrasive polishing was CDia→MechanicalCAmo→CuOCu+CO, which is a mechanical chemical polishing process. Experiments confirmed that the synergistic effects of the mechanical action and chemical reaction could increase the MRR and produce a smoother surface and less damage to the subsurface of the SCD, which provides inspiration for the processing of large-size SCD substrates.

RELATIONSHIP BETWEEN MICROSTRUCTURE, MECHANICAL PROPERTIES AND WEAR BEHAVIOR OF FRICTION STIR PROCESSED AZ31B ALLOY UNDER VARIOUS MEDIUM

Plates of AZ31B were friction stir processed in three different environments, such as liquid nitrogen, water and air with a rotational speed of 1200[Formula: see text]rpm and feed rate of 90[Formula: see text]mm/min. Microstructural studies were carried out using optical and electron microscopes, phase identification was performed using X-ray diffraction, and all specimens were tested for hardness, tensile and wear. An examination of wear debris morphology was carried out. Under cryogenic, water and air mediums, grain refinement was achieved at 1.89, 2.23 and 18.23[Formula: see text]μm, respectively. The specimen using cryogenic medium displayed greater tensile strength and elongation than the water medium. Dissolution of consistently refined grains and secondary Mg17 Al12 particles was observed after FSP underwater and cryogenic medium, resulting in a significant increase in microhardness. This surface hardening produced a significant benefit for the friction and wear behavior of the magnesium as measured by pin-on-disc configuration using a universal tribometer. With a cryogenic cooling medium, the friction coefficient is reduced by approximately 23% and the wear rate is reduced by 8% in comparison to AFSP.

Analysis of the relationship between roughness parameters of wear surface and tribology performance of 5CB liquid crystal

The aim of this work was to investigate the relationship between roughness parameters of wear surface and lubricating performance of 4-Cyano-4′-pentylbiphenyl (5CB) liquid crystal. After running-in with acetylacetone (Hacac), lubricating with 5CB realizes a significant friction reduction and generates a groove-structured wear surface with larger Sku, more negative Ssk, smaller Str, and a higher Svk/Spk, which are in good agreement with the roughness parameters that achieving lower friction. Chemical reactions in the running-in process with Hacac changes the morphology of wear debris and decreases its particle size and Si content, which are believed to be reasons for the formation of the groove-structured wear surface. Damaging the groove-structured wear surface, by introducing a process of washing up wear surfaces or lubricating with ethanol briefly between running-in with Hacac and lubricating with 5CB, changes roughness parameters of wear surface and induces higher friction coefficient. We hope this study will provide a new perspective to understand the effect of roughness parameters on tribological performance, and to provide references for surface designing.

Tribological and Thermo-Mechanical Properties of TiO2 Nanodot-Decorated Ti3C2/Epoxy Nanocomposites.

The micromorphology of fillers plays an important role in tribological and mechanical properties of polymer matrices. In this work, a TiO2-decorated Ti2C3 (TiO2/Ti3C2) composite particle with unique micro-nano morphology was engineered to improve the tribological and thermo-mechanical properties of epoxy resin. The TiO2/Ti3C2 were synthesized by hydrothermal growth of TiO2 nanodots onto the surface of accordion-like Ti3C2 microparticles, and three different decoration degrees (low, medium, high density) of TiO2/Ti3C2 were prepared by regulating the concentration of TiO2 precursor solution. Tribological test results indicated that the incorporation of TiO2/Ti3C2 can effectively improve the wear rate of epoxy resin. Among them, the medium density TiO2/Ti3C2/epoxy nanocomposites gained a minimum wear rate. This may be ascribed by the moderate TiO2 nanodot protuberances on the Ti3C2 surface induced a strong mechanical interlock effect between medium-density TiO2/Ti3C2 and the epoxy matrix, which can bear a higher normal shear stress during sliding friction. The morphologies of worn surfaces and wear debris revealed that the wear form was gradually transformed from fatigue wear in neat epoxy to abrasive wear in TiO2/Ti3C2/epoxy nanocomposites. Moreover, the results of thermo-mechanical property indicated that incorporation of TiO2/Ti3C2 also effectively improved the storage modulus and glass transition temperature of epoxy resin.

Effect of different loads on wear mechanisms of polyether-ether-ketone in normal saline and debris-isolating method

Polyether-ether-ketone (PEEK) has been proposed as a biocompatible artificial joint material. Wear particles, generated by friction between artificial joints, lead to bone resorption, aseptic loosening, and ultimately, joint failure. The size and morphology of wear particles contain information of friction and wear. Aim to obtain the wear mechanism of PEEK under different loads, this study separated PEEK debris and investigated the mechanism of wear debris and the relationship between wear mechanism and PEEK-debris morphology. An experiment was carried out with a pin-on-plate testing apparatus under different load conditions, with PEEK sliding against XLPE under saline lubrication. A method of isolating PEEK and XLPE debris from 0.9% normal saline at the same time was investigated by low-speed centrifugation. The morphologies of worn surface and wear debris were obtained based on scanning electron microscopy. The results showed that the maximum friction coefficient and minimum wear loss were 0.115 and 0.223 mg at the load of 50 N. The friction coefficient decreased and the wear loss increased with the load increase. This debris-isolation method can effectively isolate PEEK and XLPE particles larger than 200 nm in diameter. More than 96% wear PEEK particles range from 0.1 µm to 10 μm. Compared with the debris generated under the lower load condition, 0.8% more large wear particles with irregular shapes were found at a load of 150 N. The morphology of wear particles is consistent with the wear mechanism.

Classification of stages of wear in spur gears based on wear debris morphology

This work investigates the morphological changes in the wear debris, generated during the different stages of gear wear. Wear debris are generated at the mating load-bearing tooth surfaces having relative motion. The number and size of collected wear debris provide useful information for the gear fault diagnosis.
 In the present work, both online and offline analyses of wear debris are carried out for gear fault diagnosis. In the online analysis, the oil from the gear sump is passed through online wear debris counter (to estimate the number of wear particles per minute) and particle size bin. Along with the online process, the oil samples are collected periodically, and wear debris particle images are captured using a scanning electron microscope (SEM). These images are subsequently processed to determine the parameters related to the shape, size and boundary features of the particles. The results of the modified texture in different stages of gear wear are reported. The average wear mass calculated as the actual area of the wear particles is combined with particle per minute is used as the stage’s classification.
 The combined online and offline study provides a better prediction of mild wear progression along with the information on the wear mechanisms at different stages of wear. The presence of different type of particles (ferrous and non-ferrous) points to degradation of specific components.

Tribological properties of bronze surface with dimple textures fabricated by the indentation method

Surface texturing is an effective approach to improve the tribological properties of mechanical components. An indentation method is presented to fabricate dimple textures on bronze specimen surfaces. Graphite was selected as the mating balls in ball-on-disc wear tests. The worn surfaces and the indented dimples heaped with the thin ribbon debris were observed by microscope. The morphology and evolution of wear debris were employed to explain the influence of indented dimple textures. The experimental results indicate that the generation of thin ribbon debris is due to the edge hardening of indented dimple. The thin ribbon debris and the indented conical dimple are conducive to the debris heaping on slopes of dimples, which can facilitate the formation of the graphite-rich transfer layers on indented dimple surface. Compared with nontextured surface, indented dimple surface has lower coefficients of friction and slighter wear. The tribological properties of indented dimple surface are improved because of the edge hardening, the debris heaping and the formation of transfer layers.

Evolution of wear debris morphology during dry sliding of Ti–6Al–4V against SS316L under ambient and vacuum conditions

For a given tribo system one of the methods to evaluate wear mechanism is to study the evolution of the wear debris. Environmental conditions alter the wear mechanism. In the present study, Ti–6Al–4V pins of 6.6 mm diameter were slid against a SS316L disc under ambient and vacuum conditions. Morphology of worn surfaces and wear debris were analyzed by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-Ray Diffraction (XRD). At high (137.3 N) load, plate like debris were observed at low speeds under both ambient and vacuum conditions where Adiabatic Shear Band (ASB) was dominate mechanism. And an ambient condition of higher speeds produced fine wear particles where tribo oxidation (TO) and mechanically mixed layers (MML) were dominant mechanism and at vacuum condition of same speeds produced large lump wear debris due to the cause of high plastic deformation and phase transition from HCP to BCC. The analysis of the debris clearly indicates the synergism influence of three mechanisms (ASB, TO and MML) playing a role.

Tribological and corrosion behaviors of fluorocarbon coating reinforced with sodium iron titanate platelets and whiskers

ABSTRACTA series of sodium iron titanate (NFTO)–fluorocarbon composite coatings have been prepared with the liquid‐phase blending method. The effects of two types of NFTO, NFTO platelets, and NFTO whiskers, on the tribological and corrosion behaviors of the composite coatings, are systematically studied. The results show that the addition of NFTO can significantly enhance the friction‐reducing and wear resistance performances of the fluorocarbon coating. Under dry sliding, the minimum specific wear rate is 1.67 × 10−4 mm3/Nm for the platelet‐filled composite coatings and 1.15 × 10−4 mm3/Nm for the whisker‐filled composite coatings, respectively, showing a decrease of 83.5 and 88.6% than that of pure coating. Under a simulated seawater environment, the minimum specific wear rate is 5.44 × 10−5 mm3/Nm for the platelet‐filled composite coatings and 0.84 × 10−5 mm3/Nm for the whisker‐filled composite coatings, respectively, showing a decrease of 90.5 and 98.5% than that of pure coating. The morphologies of worn surfaces, wear debris, and transfer films are analyzed, and the corresponding wear resistance mechanisms are discussed. The electrochemical impedance spectroscopy certifies a remarkably improved corrosion resistance of the composite coatings which have been immersed in 3.5 wt % NaCl solution for 30 days. The composite coating reinforced with 7.5 wt % platelets shows the highest resistance of 256.3 × 106 Ω·cm2, approximately two orders of magnitude higher than that of pure coating. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48936.

Comparative study of mechanical performance between Al–Graphite and Cu–Graphite self-lubricating composites reinforced by nano-Ag particles

Copper and aluminum metals are classified relatively as softer materials that possess comparatively poor mechanical and wear characteristics; accordingly, this study has aimed an attempt to improve their properties and compare between them. At the present work, both copper and aluminum metals were used separately as a matrix composite for a comparative study. They reinforced with a fixed content of 4 vol% graphite as a solid lubricant and various content of 0, 1, 2, 3, and 4 vol% silver nanoparticles. The pure metals and the hybrid nanocomposites were manufactured by utilizing the powder metallurgy technique. Mechanical properties such as hardness, diametral compressive strength, and tensile strength were studied. Moreover, a dry wear test was performed by applying various loads of 5, 10, 15, and 20 N with constant sliding distance and speed of 1810 m and 1.5 m/s, respectively. In order to interpret the results and prove the preparation goodness, Field Emission Scanning Electron Microscope (FESEM) and Energy-Dispersive X-ray (EDX) analysis were employed to characterize the as-received composite powders, worn surface, and wear debris morphology. The results were revealed that the microhardness, diametral compressive strength, tensile strength, friction coefficient, and wear resistance were improved significantly by increasing silver nanoparticle content up to 2 vol% and 3 vol% in aluminum and copper matrix composites, respectively, and then deteriorated gradually as compared with pure metals. Convergence was observed in the wear rate results between the copper and aluminum matrix composites in the silver content of 2 vol%. Besides that, the increment in applied loads was associated negatively with the wear resistance. Lastly, the impact of improving silver nanoparticles content on strengthening the copper matrix composite is higher than aluminum matrix composite.

Tribological characterization of carbon/carbon – silicon carbide composites exposed to freezing conditions

Abstract Present article aims to investigate the tribological behavior of carbon/carbon-silicon carbide (C/C-SiC) ceramic composites exposed to freezing environment. Normal load, sliding velocity and laminate orientation were varied in this investigation. Load was varied from 20 N to 60 N in the steps of 10 N. The sliding velocities were varied ranging 1 m/s, 1.5 m/s, 2 m/s, 2.5 m/s and 3 m/s. The results showed that tribological behavior of C/C-SiC composites changed with normal load, sliding velocity and laminate orientation. Scanning Electron Microscopy (SEM) analysis of worn surfaces showed that the mechanism and synergism between wear debris morphology, adsorption and desorption of water molecules, and friction film formation described the tribological behavior of C/C-SiC composites. Coefficient of friction (COF) of composites with parallel orientation of laminates was higher as compared to normal orientation of laminates

Tribological behavior of a hydrostatically extruded ultra-fine grained Ti-13Nb-13Zr alloy

Abstract This contribution summarizes the results an investigation of the wear resistance of as received initial state and nano-structured Ti-13Nb-13Zr alloy obtained by hydrostatic extrusion. The tribological behavior was examined using a ball-on-disc tribometer under unlubricated sliding contact conditions against an Al2O3 ceramic ball. Friction coefficient, material transfer and wear debris of the samples were observed after the wear tests. Wear characteristics of the samples were investigated by means of an optical profilometer, mechanical profilometer and scanning electron microscope for wear debris morphology and wear tracks. Although friction coefficients are very similar according to tribological observations, the domestic distribution of wear characteristics varied for samples of various grain sizes. Morphological observations have shown that surface responses to abrasive ceramic balls involve localized long and short wear debris, fracture, surface plowing causing adhesive wear and the formation of larger surface debris, and material transfer between titanium and the ceramic counterpart.

Spur gear wear analysis as applied for tribological based predictive maintenance diagnostics

This paper describes an experimental investigation on a pair of spur gears in which wear and pitting were intentionally allowed to occur, namely, moisture corrosion pitting, acid-induced corrosion pitting, hard contaminant-related pitting and mechanical induced wear. A back to back spur gear test rig was used throughout 32 test series. The tests samples of wear debris were collected and assessed through the utilization of an optical microscope in order to correlate and compare the debris morphology to pitting and wear degradation of the worn gears. In addition, weight loss from all test gear pairs were assessed with utilization of statistical design. It was observed that there were significant distinctions between both weight losses, wear debris morphology generated from each induced pitting conditions and worn surface characteristics. It can be deduced that wear debris characteristics exhibited a direct relationship with different pitting and wear modes. Thus, it should be possible to detect and diagnose gear pitting and wear utilization of worn surfaces, generated wear debris and quantitative measurement such as weight loss.

The generation mechanism and morphological characterization of cutting debris based on the finite element method

Micro-cutting is a material removal mechanism with cutting debris generation, where the condition monitoring of the mechanism is important in a wear process. As a useful technique, wear debris analysis has been widely adopted for identifying the wear mechanisms in a running machine. However, there is no corresponding relationship between wear particle features and wear conditions. This paper investigates the generation mechanism of cutting debris by simulating a micro-cutting process. In particular, this study is to establish a quantitative relationship between their morphologies and cutting conditions. A three-dimensional model with a rigid pyramid sliding on the surface of #45 steel has been developed. The deformation and failure criteria of the steel are the Johnson–Cook and shear failure model, respectively. The conditions for producing cutting wear debris are studied and then the morphological features of wear debris are extracted. The main findings are as follows: (1) the critical conditions for cutting wear particle generation is jointly determined by the attacking angle and the cutting depth; (2) the width and curvature of cutting wear debris are mainly correlated with the normal load, which determines the indentation depth of the pyramid; (3) the curvature of cutting wear debris depends mainly on the sliding velocity. The understanding of the relationship between the cutting wear conditions and the morphologies of wear debris is useful for supporting debris-based wear monitoring.