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Ultralow-wear polyethylene (ULWPE) was proposed to replace conventional UHMWPE as an artificial joint material. Different molecular weights of ULWPE, ULWPE-200, ULWPE-300, and ULWPE-700 were examined against CrCoMo compared to conventional UHMWPE in multidirectional motion. The wear mechanism was elucidated from the perspective of macroscopic wear behavior and microscopic wear debris characterization. It was found that the morphologies of the ULWPE worn surface were similar to that of UHMWPE, with scratches, burnishing, and protuberances. ULWPE-700 possessed the lowest wear loss at all loading conditions, and the wear loss was 40.3% lower than that of UHMWPE at 3 MPa. Furthermore, wear debris was consistent in morphology and size range but showed differences in quantity, size distribution, and shape distribution. Combined with the wear surface morphology and wear debris analysis, it showed that plastic deformation was the main cause of wear debris formation and the wear mechanisms were adhesive wear and abrasive wear. Moreover, the FBA of ULWPE-700 was 64% lower than that of UHMWPE at 3 MPa, suggesting that ULWPE-700 wear debris had the lowest potential osteolysis. This study provides deeper insight into the bio-tribological behavior and the potential biological activity of ULWPE as an artificial joint material. [ABSTRACT FROM AUTHOR]

Polyamide 66 (PA66) is one of the commonly used polymer gear materials. This paper focuses on the tribological properties of glass fiber reinforced PA66 composites in self-mated contact using a pin-on-disc tribometer. The effects of glass fiber content, PV (the product of the contact pressure and sliding speed), and lubrication on the tribological properties of the specimens are also investigated. The results show that the glass fiber reinforced PA66 exhibit higher coefficients of friction and specific wear rates than PA66 under dry sliding conditions. This is probably due to the peeled glass fibers during the sliding process acting as abrasive particles which have an aggressive effect on the surface. Under grease lubricated conditions, PA66 + 33% GF has the lowest coefficient of friction and specific wear rate due to its higher strength. Under dry sliding conditions, all specimens show the highest friction coefficient and specific wear rate at 30 MPa·m/s with the change of PV value. Under grease lubricated conditions, all specimens show the highest friction coefficient and specific wear rate at 4 MPa·m/s with the change of PV value. The addition of grease improves friction and wear of PA66 composites under most of the experimental conditions. However, the specific wear rates of PA66 and PA66 + 13% GF under grease lubrication are higher than those under dry sliding conditions at low PV values. This may be due to the fact that greases can reduce the surface mechanical strength of PA66 and PA66 + 13% GF. [ABSTRACT FROM AUTHOR]

PA66 is a commonly used material for plastic gears due to its excellent high-temperature resistance, high strength, self-lubrication, and friction resistance. In this study, the effect of different humidity levels on the tribological properties of PA66 materials in self-mated contacts are investigated using a pin-on-disk test rig. The results show that the friction coefficient and wear rate of the PA66-PA66 sliding combination increase drastically after humidity treatment mainly due to the surface plasticization caused by water absorption and the decrease of cohesive strength and glass transition temperature. Moreover, the limiting PV value of PA66 materials decreased significantly after moisture absorption, and when the actual PV value exceeds this reduced material limit, the degree of friction and wear increases drastically. The wear mechanism of the PA66-PA66 sliding combination is mainly adhesive wear without humidity treatment. The wear mechanism is adhesive wear combined with abrasive wear after humidity treatment (50%, 70%, 90%, immersion in water) and abrasive wear is most significant at 50% humidity. Abrasive wear decreases with the increase of the moisture content, while adhesive wear increases. [ABSTRACT FROM AUTHOR]

The tribological behavior of nickel-based superalloy blades with YSZ ceramic-based abradable coatings was investigated using a self-developed high-speed rubbing tester, focusing on the effect of working parameters (linear velocity and incursion rate) on blade and coating wear mechanisms. A non-contact infrared thermometer and a high-speed camera were used to determine real-time changes in coating surface temperature and blade length. The wear morphology and elemental composition of the blade and coating were characterized by a scanning electron microscope, an ultra-depth three-dimensional microscope, and an energy spectrometer. The test results showed that at the same incursion rate, the variation of blade wear length exhibited a tendency of first increasing and then decreasing with the increase of linear velocity. The maximum degree of blade wear was reached at 200 m/s. There was no significant correlation between the degree of blade wear and the incursion rate at the same linear velocity. The linear velocity was the primary influence on driving friction, while the incursion rate became a secondary factor, contrary to the well-known law in metal-based abradable coatings. The main forms of damage to blades included grooving, overheating, and micro-rupture. Plastic removal was the main wear mechanism for blades. The wear mechanism of ceramic-based abradable coatings was mainly characterized by subsurface cracking. The brittle removal of the coating resulted in “stepped” wear of the blade and a short actual action time of the friction pair. In this paper, the wear mechanisms of nickel-based superalloy blades and ceramic-based abradable coatings were mapped for the first time. [ABSTRACT FROM AUTHOR]

Considering the relevance of Inconel 718 alloy for the oil and gas industry and the nature of the tribological system to define the friction and wear behaviors during sliding, this investigation presents results obtained in reciprocating tests under saline solution for active-screen plasma-nitrided Inconel 718. Bearing steel and silicon nitride ceramic were used as counterbodies, balls of 4 mm diameter. Extensive plastic deformation was confirmed using nanoindentation analysis, and oxidation governed the tribological responses when the steel ball was used as a counterbody. In these conditions, the presence of a nitrided layer was significant in reducing wear by one order of magnitude. On the other hand, when the ceramic ball was tested, abrasive wear was the primary mechanism, and the nitrided layer did not affect either the friction or the wear rate of Inconel 718. The corrosion behavior helped to confirm the predominance of described wear mechanisms. [ABSTRACT FROM AUTHOR]

Cr–Ni–Mo–V steels usually exhibit excellent performance under high-temperature friction and wear conditions. However, after hot rolling with a certain amount of deformation, Cr–Ni–Mo–V steels usually exhibit a banded microstructure, which significantly affects their mechanical properties and wear performance. In this study, the wear behavior and mechanical properties of two Cr–Ni–Mo–V steels with different grades of banded structures were studied at room temperature, 100 °C, 300 °C, and 500 °C. The results show that the specimens with higher grades have lower hardness at room temperature to 300 °C but exhibit better wear resistance. This is because the banded structure results in a microstructure with an alternating distribution of coarse and fine grains, which increases the work-hardening capacity. At 500 °C, the wear rate of higher grade specimens increased steeply owing to severe oxidative wear. This study provides relevant guidelines for the high-temperature wear mechanisms of steels with banded structures. [ABSTRACT FROM AUTHOR]

Copper matrix composites with carbon nanotubes/Cu composite foams as the reinforcing skeletons (CNTs/Cuf®Cu) were prepared by electrodeposition and spark plasma sintering. The microstructure and tribological properties of the composites were studied. The CNTs reinforcements with the content up to 0.283 vol% remained uniformly distributed in the skeleton zone and led to quite different structure and properties as compared to the pure copper zone. Significant reduction of the friction coefficient and wear rate was shown with CNTs reinforcements in the skeleton up to a certain content. The wear surface morphology was analyzed and the possible wear mechanism was discussed for the composites with such an inhomogeneous structure. [ABSTRACT FROM AUTHOR]

Cermets have been widely used in industry to combat wear and erosion because of their elevated strength and hardness and good wear resistance. This study investigated the tribological properties of WC-6Ni (YN6X), WC-6Co (YG6X), and WC-TiC-Co–Ni (TiCN) cermets during sliding over silicon carbide (SiC) in prepared seawater. Tribological experiments of 440C and GCr15 steel coupled with SiC were conducted for comparison. The influence of sliding speed was examined by multiple sequential increases in speed from 0.1 to 0.4 m s−1. The results showed that the tribological properties of the tribopairs were enhanced with growing sliding speed and were influenced by complex factors including material hardness, wear radius, the lubricating medium environment, and the tribochemical reaction. YN6X performed particularly well due to its high hardness and presence of Ni which effectively reduced the corrosion effect of seawater. However, YG6X showed better wear resistance relative to YN6X in tap water due to its higher hardness. In particular, through an investigation of the wear process of the tribopairs in seawater, this study proposed the coefficient of friction model for cermet/SiC. The results indicated that a combination of YN6X/SiC has excellent potential for application to seawater hydraulic components. [ABSTRACT FROM AUTHOR]

The nickel-based single crystal (NBSC) superalloy has been widely used in aero engines, gas turbines, and other power plants due to its excellent high-temperature performance. During the working process, wear often occurs on the contact surface of the NBSC superalloy, which will promote crack nucleation and reduce its working life. In this work, the dry-sliding friction and wear behaviors of NBSC superalloy with < 001 > crystallographic orientation at different temperature and loading conditions are investigated by using a ball-on-disc tribometer. Results show that both the friction coefficient and wear rate of the NBSC superalloy are high at room temperature, and both them are significantly reduced as the temperature rises to 600 ℃ and 700 ℃. Analysis of the worn morphologies and cross-section SEM micrographs shows that a compacted glaze-layer is formed at high temperatures like 600 ℃ and 700 ℃ during the early stage of wear process, acting like a lubricant between the superalloy and rubbing ball. Hence, the change in wear mechanism caused by temperature leads to significant change of wear behaviors. In contrast to temperature, the magnitude of load has less effect on the wear mechanism. [ABSTRACT FROM AUTHOR]

This study focuses mainly on potential skin abrasion risks that are likely to be caused by the interactive force on a contact surface between a human body and a physical assistant robot's cuff, particularly when these robots are misused. In this study, we develop a novel method for evaluating skin contact states in order to estimate abrasion risks. First, a simplified cuff model is designed to conduct abrasion tests on a piece of dummy skin. The skin is pasted onto a dummy's leg to simulate the human skin's viscoelastic properties. Then, the edge condition of the contact surface is measured while the cuff model slides on the dummy skin. We conduct an analysis of the interactive force and displacement between the cuff model and dummy skin and several principal influential factors are examined during the evolution of abrasion-induced skin damage. These results are applied to evaluate the contact conditions between the robot's cuff and human skin, which makes a significant contribution to estimating the risk of abrasion injuries for a physical assistant robot user. [ABSTRACT FROM AUTHOR]

The wear properties and wear mechanism of WC-13%Ni hard alloy irradiated by high-intensity pulsed electron beam (HIPEB) at energy density of 34 J/cm with pulse numbers of 1-10 were investigated by dry sliding wear tests. The phase structure, cross-sectional microstructure and microhardness-depth profiles of the irradiated WC-13Ni hard alloy were examined by using X-ray diffractometer, scanning electron microscopy and Vickers testers, respectively. It was found that HIPEB irradiation induced surface remelting and preferentially ablation of Ni binder phase, resulting in the formation of a modified layer composed of remelted top layer accompany with WC phase transformation and graphite phase precipitation, and shock hardening layer. The specific wear rate of the irradiated samples decreased with the increasing pulse number and reached a minimum value of 3.8 × 10 mm/N m with 10 pulses, only for 32% of the non-irradiated samples. The wear mechanism of surface remelting top layer on the irradiated samples was a homogenous microabrasion wear, which was attributed to the surface remelting and phase transformation, and the wear of the shock hardening layer involved preferential removal of Ni binder phase and detachment of WC grains, but it was restrained by strengthening of Ni binder phase from the deep hardening of HIPEB irradiation. [ABSTRACT FROM AUTHOR]

The effect of the element cerium on the microstructure and wear behavior of Fe-B cast alloy was investigated by scanning electron microscope, transmission electron microscope, X-ray diffraction analysis, Leica digital image analysis, hardness tester and abrasion tester. The microstructures of as-cast Fe-B alloy are composed of the phase ferrite, pearlite and eutectic boride. Moreover, the as-cast eutectic boride structures in Fe-B alloy containing cerium are finer than that in the alloy having no cerium. After heat treatment, the average boride area and wear weight loss of the alloy containing cerium are lower than these of the alloy having no cerium. Before the formation of primary austenite, cerium can combine with oxygen to form CeO. CeO can act as nuclei of primary austenite, promoting the refinement of austenite and borides during solidification, and improve the wear property of Fe-B alloy. [ABSTRACT FROM AUTHOR]

This study investigates the effect of titanium and nitrogen elements on the microstructures and wear behaviors of medium carbon Fe-B cast alloy. The as-cast microstructures of Fe-B cast alloy consist of the eutectic boride, pearlite, and ferrite. Moreover, the as-cast eutectic boride structures are greatly refined when titanium and nitrogen are added. The boride area fraction, average boride area, Rockwell hardness, etc., are also investigated systemically. The wear behaviors of medium carbon Fe-B cast alloy are studied by a three-body abrasive wear tester. The results show that the wear weight loss of Fe-B cast alloy with titanium and nitrogen elements is lower than that of the ordinary Fe-B cast alloy. Meanwhile, the wear mechanism of Fe-B cast alloy with different titanium and nitrogen concentrations is described and analyzed. [ABSTRACT FROM AUTHOR]

The wear behavior of pure carbon strip against copper (carbon/copper pair) under continuous arcing condition was investigated. To simulate the extreme condition of continuous arc discharge at high current, sliding wear tests were conducted on a home-made wear tester. The arc erosion wear characteristics and mechanisms of carbon/copper pair were studied by analyzing the wear scars and wear debris of the carbon strip in detail. Therefore, various analytical techniques, including Raman spectroscopy, transmission and scanning electron microscopy, and focused ion beam systems, were utilized to characterize the wear scars and wear debris of the carbon strip. The results show that the wear rate and the degree of arc erosion of the carbon strip increase with increasing electric current density. Typical entwined turbostratic carbon nanospheres (ETCNs) exhibited sphere-like stacking structure that were observed in the microstructure of the wear debris of the carbon strip produced during the friction process with current, which is the characteristic of the textural changes in carbon materials under combined arcing and sliding friction conditions. Moreover, the number and size of ETCNs increase with the electric current density increase. The arc erosion wear mechanisms of the carbon/copper pair are mainly due to the synergetic action of oxidation ablation, local electric arc impact and high-temperature graphitization under continuous arcing. [ABSTRACT FROM AUTHOR]

The tribological behavior of self-mated TiSiC in low viscosity fluids, that is, water and ethanol, is investigated. The results show that both water and ethanol effectively reduce the friction and wear of self-mated TiSiC. The friction coefficient and total wear rates of TiSiC tribo-pair are 0.82 and 2.17 × 10 mm/N m under dry condition, 0.41 and 6.50 × 10 mm/N m in water and 0.16 and 2.22 × 10 mm/N m in ethanol. As sliding distance is prolonged from 0.5 to 22.9 km, the total wear rates of TiSiC in ethanol can be further reduced. Mechanical wear of TiSiC is partly inhibited in water and greatly inhibited in ethanol. Surface polishing of TiSiC pin and tribochemistry are the two distinct characteristics of self-mated TiSiC in ethanol. The surface film in ethanol is composed of TiO and SiO. Tribo-products in ethanol, that is, silica gel and titanium dioxide, are found. Polycondensation of ethanol by the catalysis of TiO and SiO gives birth to paraffins and olefins. [ABSTRACT FROM AUTHOR]

A laminar-structured tribolayer on the worn surface of Cu-SiO composite in sliding against 1045 steel is observed by etching the longitudinal sections. In morphology, the tribolayer consists of many subunits with different lengths and heights. The subunits are curved or parallel to the contact surface at different depths from bulk to the worn surface. In microstructure, the tribolayer is unconsolidated after etching, and fine Cu grains, as well as few fractured SiO particles, are observed. The main formation mechanism of the laminar-structured tribolayer is grain boundary sliding. Shear localization with large plastic strain is a prerequisite for the formation of laminar structure. The generation and accumulation of frictional heating promote the plastic deformation and decrease the activation energy for grain boundary sliding. The etching effect is contributed to the presentation of the laminar structure. [ABSTRACT FROM AUTHOR]

Wear is one of main obstacles to expand functions of microelectromechanical systems (MEMS). While the wear mechanism of surface-fabricated MEMS devices has been extensively investigated, the characteristics of bulk-fabricated Si-MEMS devices have hardly anywhere been reported. In this research, wear tests of bulk-fabricated Si-MEMS devices were carried out on a composite microtribology test system using out-of-chip loading and driving mechanisms. Wear evolution and the effects of initial topology, driving frequency and external normal load have been investigated over the running time from 5 s to 120 min. A transition from adhesive wear to abrasive wear has been observed, which is conceptually analogs to the wear process in surface-fabricated devices. The results of the experimental study indicate that plastic deformation of the silicon substrate down to nano-size and migration of the wear debris are the main characteristics of wear. When the normal load is >56 μN, wear particles can be grinded into pie or mud shape. At driving frequency higher than 2,000 Hz, the agglomerated wear debris can be thrown out of the contact zone, while at 100 Hz it remains on the rubbing surface and causes evolutionary damages. The energy consumption during wear has been estimated by tests at elevated temperatures, which is helpful to understand the poor wear resistance and the mechanical dominant mechanism of wear. [ABSTRACT FROM AUTHOR]

Silver-based composite with 15 vol% MoS and with 5 vol% graphite was prepared by powder metallurgy method. The impacts of the counterface materials, atmosphere, and temperature on the tribological behavior of the composite were investigated. It was found that when sliding against brass less effective lubricating film formed, causing a higher friction and wear comparing with ASTM-1045 steel. With the increasing proportion of oxygen in the O/N atmosphere, the wear rate and friction coefficient ascended slightly. At 200 °C, the combination lubrication of graphite, MoS, and Ag contributed to a low friction coefficient (0.07) and wear rate (6.56 × 10 mm/Nm). At 400 °C, graphite lost its lubricating role, while silver became excessively soft. Large amount of MoS was oxidized into MoO and the residual MoS formed some island-like lubricating films. Severe adhesive wear occurred on the contact surface, which led to a high friction coefficient (0.25) and a great increase of the wear rate (23.2 × 10 mm/Nm). At 600 °C, a relatively low friction coefficient (0.1) was obtained because of the formation of high-temperature solid lubricants, (AgMoO and AgMoO) and liquid AgMoO. However, the wear rate at 600 °C was the highest (32.6 × 10 mm/Nm) due to the thick transfer layer. [ABSTRACT FROM AUTHOR]

The microstructures of Fe-B alloys containing different carbon and boron concentrations have been investigated. The solidification microstructures of Fe-B alloy consist of the eutectic boride, pearlite, and ferrite. Borides precipitate along the grain boundary during the formation of eutectic. After heat treatment, the phases in Fe-B alloy are composed of the boride and martensite. With increase of carbon and boron concentrations, the Rockwell hardness of Fe-B alloy becomes larger. Meanwhile, by using a pin-on-disk abrasion tester, the effects of carbon and boron concentrations on the wear behaviors including ploughing depth, roughness, and wear weight loss under different loads have been studied. The results show that the wear resistance of Fe-B alloy with higher carbon and boron concentrations is comparable with the high chromium white cast iron. [ABSTRACT FROM AUTHOR]

The torsional wear behavior of monomer cast nylon (MC nylon) composites reinforced with glass fiber was studied with a self-made torsional friction tester. The worn surface of MC nylon composites was investigated with a scanning electron microscope. The worn surface of the steel disk was observed with a 3-D profiler. The experimental results indicated that the shape of torque-angular displacement ( T- θ) curves changed from elliptic shape to quasi-parallelogram with the angular displacement increased from 5° to 30°. The serious wear characterized with a deep groove occurred at the position of about 1.5-4 mm radius of contact zone on the steel surface. The mass of MC nylon samples increased after torsional wear test. The torsional contact area can be divided into three zones: (a) a central stick zone, (b) an intermediate mixed-slipping annulus, and (c) a peripheral sliding annulus. The most serious wear occurred in the intermediate annulus because of the higher contact stress and mixed slip regime. The main wear mechanism of MC nylon samples was adhesive wear and abrasive wear. Plastic deformation of asperities was the character in the central zone. Slight adhesive wear was the main wear mechanism in the peripheral annulus. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effect of SiC particle size on the wear properties of magnesium-based hybrid metal matrix composites (MMCs) reinforced with Saffil short fibers and SiC particles. Hybrid MMCs with different SiC particle sizes of 1, 7, and 20 μm, respectively, were fabricated by the squeeze infiltration process. The volume fractions of Saffil short fibers and SiC particles in the hybrid composites were 15 and 5%, respectively. Wear tests were carried out using a ball-on-disk against a steel ball under the dry sliding condition. The test results showed that the composite with large-sized SiC particles had an improved wear resistance compared with the smaller sized particles. [ABSTRACT FROM AUTHOR]

The tribological behaviour of Fe-28Al-5Cr and its composites containing 15, 25 and 50 wt% TiC (corresponding to 19.3, 31.2 and 57.6 vol%), produced by hot-pressing process, was investigated under liquid paraffine lubrication against an AISI 52100 steel ball in ambient environment at varied applied loads and sliding speeds. It was found that the wear resistance increased and friction coefficient decreased with increasing of TiC content. The coefficients of friction are in the range of 0.09-0.14 at the given testing conditions. The wear rates of all the materials except the 50% composite are on the order of 10-10 mm m, the wear rate for the 50% composite is too low to quantify under the two sliding conditions, (50 N, 0.04 m/s) and (100 N, 0.02 m/s). The wear rates of all the materials increase as applied load increases and the increasing extent diminishes with the increase of TiC content, but first increase slightly and then nearly remains steadiness with increasing sliding speed. The 50 wt% composite has wear resistance about 7-20 times better than pure Fe-28Al-5Cr at different sliding parameters. The enhanced wear resistance by TiC addition is attributed to the high hardness of the composites, as well as support of the oil lubrication film/layer by the hard TiC phase. The worn surfaces of all the materials are analyzed by a scanning electron microscope. The dominant wear mechanism of the Fe-28Al-5Cr and 15% composite is grooving and flaking-off, but those of the 25 and 50% composites are mainly shallow grooving. [ABSTRACT FROM AUTHOR]

The friction and wear of monolithic polyamide 66 (PA66) and a PA66 composite reinforced with short glass fibers were examined using a block-on-ring friction tester with particular focus on the effect of weight average molar mass ( M) of PA66. The amount of glass fibers in the composite and the molecular weight strongly affected the friction level and wear rate because it altered the shear strength and adhesion of PA66. In the case of the glass fiber-reinforced PA66 composites, the improvement of the tribological property was attributed to the increased softening temperature of the composite and reduced material transfer to the counter surface. From this study, the optimum composite having the improved wear resistance with the low friction level was achieved with the lower M PA66 containing 40 vol.% glass fibers. [ABSTRACT FROM AUTHOR]

A HfB-containing Ni-based composite coating was fabricated on Ti substrates by laser cladding, and its microstructure and tribological properties were evaluated during sliding against an AISI-52100 steel ball at different normal loads and sliding speeds. The morphologies of the worn surfaces were analyzed by scanning electron microscopy (SEM) and three-dimensional non-contact surface mapping. The results show that wear resistance of the pure Ti substrate and NiCrBSi coating greatly increased after laser cladding of the HfB-containing composite coating due to the formation of hard phases in the composite coating. The pure Ti substrate sliding against the AISI-52100 counterpart ball at room temperature displayed predominantly adhesive wear, abrasive wear, and severe plastic deformation, while the HfB-containing composite coating showed only mild abrasive wear and adhesive wear under the same conditions. [ABSTRACT FROM AUTHOR]

In this investigation, three Fe-Cr-C hardfacing alloys with different carbon and chromium contents and in constant ratio of $$ \left( {\frac{Cr}{C} = 6} \right) $$ were fabricated by GTAW on AISI 1010 mild steel substrates. The OES, OM, SEM, and XRD techniques and Vickers hardness method were used for determining chemical composition, hardness, and studying the microstructure of the hardface alloys. The OES, OM, and XRD examination results indicated that different carbon and chromium contents of hardface alloys produced hypoeutectic/eutectic/hypereutectic structures. By increasing the carbon and chromium contents in the chemical composition of hardface alloys, the volume fraction of the total (Cr, Fe)C is increased resulting to decreasing in total the austenite volume fraction and increasing the hardness of the surface. Studying the microstructure after wear test (ASTM G65) shows that at the edge of the worn surface, the transformation of austenite to martensite had occurred in all the samples. The wear test results indicate that the highest wear resistance is gained in the hypoeutectic structure with maximum hardness after the wear test. In addition, abrasive wear micromechanisms in hypoeutectic/eutectic/hypereutectic were recognized as: ploughing + cutting/ploughing + cutting + cracking/cracking + cutting, respectively. [ABSTRACT FROM AUTHOR]

Fe-based composite coatings reinforced with TiC particles were prepared by laser surface engineering from precursor of ferrotitanium and graphite. Microstructure of the composite coatings was comprised of dendritic TiC dispersed in a ferrite matrix. In situ dendritic TiC was formed by mechanism of precipitating from the liquid Fe-Ti-C alloy system. Composite coatings showed a substantial increase in microhardness in comparison to that of the substrate. Dry sliding wear tests performed at room temperature revealed that the in situ composite coating possessed a considerably reduced wear volume loss owing to the presence of in situ synthesized TiC. A relatively smooth surface was observed for in situ TiC/Fe composite coating due to its high resistance to ploughing and adhesion, which is caused by the uniformly dispersed TiC reinforcement with high volume fraction. [ABSTRACT FROM AUTHOR]

The effect of surface conditions and secondary phase addition on the dry sliding friction and wear characteristics of five yttria-stabilized ZrO-based composites with 40 vol% WC, TiCN or TiN was investigated using an ASTM G133 pin-on-flat sliding contact configuration. WC-6wt%Co-cemented carbide pins were used as mating material. The friction and wear level were higher for wire-EDMed ZrO-based composites compared to their equivalent ground specimens. This finding could be correlated to flexural strength measurements, revealing strong discrepancy between wire-EDMed and ground surfaces. The most favorable tribological characteristics were encountered with ZrO-WC composites compared to ZrO-TiCN and ZrO-TiN grades. [ABSTRACT FROM AUTHOR]

This study investigates the effect of semi-solid processing on the microstructures, mechanical properties of low carbon Fe-B cast alloy. The as-cast microstructure of Fe-B cast alloy consists of the eutectic boride, pearlite, and ferrite. Compared with the coarse eutectic borides in the ordinary alloy, the eutectic boride structures in the semi-solid alloy are greatly refined. Moreover, the boride area fraction, Rockwell hardness, impact toughness, etc., before and after heat treatment under different casting methods are also investigated systemically. The wear behaviors of low carbon Fe-B cast alloy are studied by three-body abrasive wear tester. The wear weight loss of semi-solid Fe-B cast alloy is lower than that of the ordinary Fe-B cast alloy because of the lower average boride area for semi-solid specimen. Meanwhile, the wear mechanism of the low carbon Fe-B cast alloy under different casting process is depicted and analyzed by using the physical models. [ABSTRACT FROM AUTHOR]

The hydrogenated amorphous carbon (a-C:H) films were prepared on AISI 440C steel substrates using a RF magnetron sputtering graphite target in the CH4 and Ar mixture atmosphere. The friction and wear behavior of a-C:H films were comparatively investigated by pin-on-disc tester under dry sliding and simulated sand-dust wear conditions. In addition, the effects of applied load, amount of sand and sand particle sizes on the tribological performance of a-C:H films were systemically studied. Results show that a-C:H films exhibited ultra-high tribological performance with low friction coefficient and ultra-low wear rate under sand-dust environments. It is very interesting to observe that the friction coefficient of a-C:H film under sand-dust conditions was relatively lower when compared with dry sliding condition, and the wear rate under sand-dust conditions kept at the same order of magnitude (×10−19 m3/N m) with the increase of applied load and particle size as a comparison with the dry sliding condition. Based on the formation of “ridge” layer (composite transfer layer), a transfer layer-hardening composite model was established to explain the anti-wear mechanisms and friction-reducing capacity of a-C:H solid lubrication films under sand-dust conditions. [ABSTRACT FROM AUTHOR]

TiC reinforced AZ91 magnesium matrix composites have been fabricated by a melt in situ reaction spray deposition. The microstructures of spray-deposited alloys were studied by using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The dry sliding wear behavior of the alloys was investigated by using a pin-on-disc machine under five loads, namely 10, 20, 30, 40, and 50 N. The composites had much better wear-resistance than the matrix alloy. The wear behavior of the composites was dependent on the TiC content in the microstructure and the applied load. The improvement in the wear resistance of the composites became more prominent at larger normal load. At a lower load (10 N), with increasing TiC content, the wear rate of the composite was decreased, and the dominant wear mechanism was an oxidative mechanism. At a higher loads (50 N), a spray-deposited AZ91/TiC composites exhibited superior wear resistance to the AZ91 magnesium alloy, and the dominant wear mechanism was delamination. [ABSTRACT FROM AUTHOR]

This paper investigates the mechanism of wear-particle generation when a single asperity is passed over the surface of UHMWPE. A single asperity is modelled using a conical diamond-tip indenter attached to a nano-scratch tester. Scratches are produced by passing the indenter over the surface of the polymer in a single pass and multiple passes on a single track or on orthogonally intersecting tracks. The debris-generation process, as observed in the nano-scratch test, is complex and depends upon the direction of scratches. It is found that the rate of wear-debris generation is much higher when two consecutive scratches orthogonally intersect each other compared to when the scratches are made on the same track. “Wall” formation was observed between orthogonally intersecting scratches, and it is believed that this is central to the low-cycle wear mechanism in these systems. [ABSTRACT FROM AUTHOR]

Commercially available, slightly porous monolithic alumina was modified using CO2-laser irradiation by embedding zirconia, titanium nitride and tungsten carbide. The thickness of the modified surface layers was 550 μm after laser treatment and the composition of the multiphase microstructures depended on the laser process and the additives used. Tribological tests were carried out on the ceramics using a laboratory tribometer in unlubricated, oscillating sliding contact at room temperature against alumina balls. The wear mechanisms during running-in were analysed by short-time tests and studies of the worn surfaces by SEM. [ABSTRACT FROM AUTHOR]

Tribological performance of diamond-like carbon (DLC) overcoat on a magnetic hard disk was evaluated using a contact start stop wear tester. The analysis of worn surfaces suggests that wear of the carbon overcoat took place by a delamination type of wear mechanism at a nanoscale, resulting in the formation of wear particles of about 1.5 nm thick and 30–90 nm wide. [ABSTRACT FROM AUTHOR]

The friction disc and the impeller ring of a switchable water pump (SWP), having a similar principle to that of the wet clutch of an automobile, but it also exhibits a relatively low pressure, a high velocity and temperature. However, SWP possesses an inadequate friction coefficient that has a high tendency to result in the relative slip and severe wear of the counterparts. To acquire such a friction material with an improved friction coefficient and wear resistance to satisfy the new operating condition of SWPs, brass-based composites reinforced by SiO2 nanoparticles were successfully fabricated by the powder sintering in this study, and the influence of the mass fraction of SiO2 nanoparticles on the friction and wear behaviour of the composites was also discussed. The results show that the composite with an appropriate mass friction of SiO2 nanoparticles up to 5 wt% exhibited a homogeneous microstructure. Meanwhile, the friction coefficient was raised to 0.23 with a wear volume reduced to 7.3 × 10− 5 mm3, and the predominant wear mechanism changed from adhesive wear to abrasive wear, due to its enhancement of the densification level and the Vickers micro-hardness. [ABSTRACT FROM AUTHOR]

Dry sliding friction and wear behavior of nitrided and non-nitrided spray-formed Al alloys against AISI52100 steel were investigated using a linear-reciprocating ball on flat configuration under different normal loads. In case of nitrided spray-formed Al alloys, an increase in the applied normal load leads to a steady reduction of the stationary stage of the coefficient of friction depending on the sustainability of the AlN/Al compound. With regard to the nitride layer, thickness-specific wear regimes are distinguished for both spray-formed Al alloys. Nitrided spray-formed AlSi alloys show mild abrasive wear independent of normal load in case of AlN layers with up to 3 µm thickness. The layers exhibit an increased wear resistance compared to the non-nitrided condition for all applied test loads. Thick AlN layers > 4 µm show a steep increase in wear rate at loads exceeding 10 N, indicating a severe adhesive wear. These layers fail due to nitride layer delamination. Nitrided spray-formed AlMg alloys show mild abrasive wear for thin AlN layers < 4 µm up to normal loads of 12 N. Thick AlN layers almost immediately fail upon the initiation of the sliding contact due to crack formation within the nitride layer. [ABSTRACT FROM AUTHOR]