A relation between wear volume and sliding time for composite materials

Friction and wear experiments on two graphite fiber-aluminum matrix composites and two commercially pure metals (aluminum and copper) were conducted on a brake-type friction machine. The counterface material was graphitic cast iron. The composite samples were tested with the graphite fibers perpendicular to the counterface; the load varied from 5 to 100 N. The initial sliding velocity varied from 2.0 to 11.4 m s^?1. The wear resistance of the HM-Al 1100 graphite fiber-aluminum matrix composite was found to be more than one order of magnitude better than that of the unreinforced matrix material. With aluminum and copper, the wear volume per braking cycle is proportional to the product of load and sliding distance in accord with both the adhesion and delamination theories of wear. For the two composite materials studied, the wear volume per braking cycle is proportional to the product of load and sliding time which cannot be explained by either of the two wear models. Thus the wear mechanism of composites might be fundamentally different from that of pure metals.     

Sliding wear behaviors of in situ alumina/aluminum titanate ceramic composites

In situ alumina/aluminum titanate ceramic composites were prepared by spark plasma sintering with two kinds of alumina/titania powders, which are microsized irregular particles (referred to M powder) and microsized spherical particles composed of nanosized grains (referred to N powder). The phase constitution and microstructures of the powders and as-prepared ceramic composites were characterized by using X-ray diffractometer (XRD) and scanning electron microscope (SEM). The sliding wear behaviors of two alumina/aluminum titanate ceramic composites were investigated by ball-on-disc wear test with varied normal loads. The worn surfaces of ceramic composites and counterpart Si₃N₄ balls were characterized by using SEM equipped with X-ray energy dispersive spectroscopy (EDS). The results showed that the wear volume of two ceramic composites increased with increasing the normal load. Under the same normal load, the wear volume of N composite (obtained from the N powder) was higher than that of M composite (obtained from the M powder). Two different behaviors were identified: N composite showed intergranular fracture and grain pull-out; however, the surface reaction layer formed in M composite presented plastic deformation. The different behaviors are controlled by two different mechanisms, brittle fracture mechanism for N and tribochemical reaction mechanism for M. The different wear behaviors for the two ceramic composites were discussed in detail.     

Abrasive wear of some commercial polymers

Cylindrical test pins of some commercial polymer-based bearing materials (comprising two nylons 6, a filled nylon 6/6, a filled ultra-high molecular weight polyethene (uhmwpe) and three polyurethanes) were rotated, in dry conditions and at constant load and sliding speed, on circular tracks on stationary discs of steel gauze and abrasive paper.Wear against run-in steel gauze was proportional to the sliding time (distance), with the specific wear rate, v_sp, (wear volume per unit area per unit sliding distance) varying with the nominal pressure, p, according to v_sp = Kp^α. Values of K and α are presented enabling comparison of the fatigue wear of the materials at various loads against steel (or a counterface with rounded asperities) in non-transfer film conditions. Nylon 6 showed the least wear and the polyurethanes showed the greatest wear, up to pressures of 3.43 MN m^?2 (500 lbf in^?2).With abrasive paper, the circular path became progressively clogged with transfer films and wear debris, and the wear volume, ΔW, diminished with time, t, throughout the test duration, following the relationship ΔW = Dt^c, where both c and D are functions of the wear path diameter. c appears to be related to the film transfer capability of the polymer. The best overall abrasive wear resistance (in transfer film conditions) was exhibited by the filled uhmwpe, followed by two polyurethanes. Nylon 6 showed relatively poor abrasion resistance under these conditions. The mechanical properties indicate, with one exception, a similar ranking order for non-transfer film conditions     

Effect of temperature and load on three-body abrasion of cermets and steel

The effect of temperature and load on three-body abrasion resistance has been examined for stainless steel, Cr₃C₂-Ni cermet, plain WC-Co hardmetal and yttria stabilized zirconia doped WC-based composites. Series of tests at various tribo-conditions were performed on a recently developed device. Coefficient of friction and materials response to abrasive actions have been analyzed and positive effect of zirconia addition on materials wear resistance has been shown. The low wear rates of ZrO₂ containing cermets are due to lower susceptibility of zirconia to transgranular crack propagation, smaller mean free path between ceramic grains and formation of lubricating glazed silica-rich layer.     

Comparison on abrasive wear of SiCrFe, CrFeC and Al2O3 reinforced Al2024 MMCs

The effects of volume fraction and size of SiCrFe, CrFeC, and Al₂O₃ particulates on the abrasive wear rate of compo-casted Al2024 metal matrix composites (MMCs) were studied. The process variables like the stirring speed, position and the diameter of the stirrer have affected the diffusion between particulates and matrix.The abrasive wear rate was decreased by the increase in particulate volume fraction of SiCrFe and CrFeC intermetallic reinforced composites over 80 grade SiC abrasive paper. The wear rates of the all composites decreased with aging treatment, and the best result was seen for the composite having a hybrite structure as SiCrFe and CrFeC particulates together. Nevertheless, the fabrication of composites containing soft particles as copper favors a reduction in the friction coefficient.     

Friction and wear behaviour of aluminium alloy coconut shell char particulate composites

The friction and wear characteristics of Al-11.8%Si alloys containing 10–25 vol.% (3–8 wt.%) dispersions of coconut shell char particles (average size, 125 μm) were evaluated under dry conditions with a pin-on-disc machine. At the lower sliding speed of 0.56 m s^?1, the wear rates and friction coefficients of the composites decreased with increasing volume per cent of dispersed char particles in the aluminium alloy matrix. Scanning electron microscopy observations have revealed the presence of adhering shell char fragments on the worn-out surface of the composites and the average roughness R_a for the worn-out surface of the composite (Al-11.8%Si-8%char) was much less (1.9 μm) than for the worn-out surface of the matrix (3.2 μm). At the higher sliding speed of 5.38 m s^?1, the wear rates increased with increasing volume per cent of dispersed char particles in the matrix and the R_a value for the composite (Al-11.8%Si-8%char) was higher (5.2 μm) than for the matrix (4.6 μm). The worn-out surface of the composites did not show the presence of adhering shell char fragments. The reduction in wear rates and friction coefficients of composites at the lower sliding speed of 0.56 m s^?1 with respect to the matrix alloy wear was attributed to the presence of adhered fragmented bits of shell char on the wearing composite surface.     

Dry sliding wear of diamond materials

In pin-on-disc tests, diamond composites, consisting of diamonds imbedded in a silicon matrix, were run against themselves in air at a sliding speed of 125 cm s^?1 and for loads up to 3.6 kgf. In addition, a few experiments involving sintered diamond compacts rubbing against a rotating metal ring in a ring-and-block configuration were conducted. For the diamond composite wear tests, wear was found to be proportional to load and sliding distance for P ? 3.0 kgf. For both the diamond composite and the diamond compact, the wear rates were very low and similar to those previously observed for single-crystal diamonds rubbed by diamond and metal.     

Dry sliding wear properties of unhybrid and hybrid Al alloy based nanocomposites

Abstract

Nanosize B₄C and/or MoS₂ particles reinforced AA2219 alloy composites were prepared using the stir casting process. The wear properties were evaluated for several speed (3.14–5.65 m s^?1), load (10–50 N) and distance (0–2500 m) conditions. The nanoparticles dispersion, density, wear resistance, morphology of the worn surface and loose wear debris were discussed in detail. The wear resistance improvement results by nanoparticle addition correspond well with the hardness. Between the nanocomposites, hybrid composites show significantly higher wear resistance for all load, speed and sliding distance conditions. The better wear resistance is attributed to the matrix strengthening by nanoparticles and the lubricant-rich tribolayer controlled wear in the hybrid composites. The intensity of abrasive, oxidation and delamination wear mechanisms decide the wear rate at any particular wear testing condition.     

Abrasive wear of WC-FeAl composites

The abrasive wear behavior of tungsten-carbide iron-aluminide composite materials was investigated using a pin-on-drum wear-testing machine. Samples were prepared by uniaxially hot pressing blended powders. The wear rates of specimens containing 40 vol.% matrix of atomic composition, Fe₆₀Al₄₀, were measured and results compared with those of conventional WC-10 vol.% Co hardmetal. They were found to be comparable to those of WC-10% Co hardmetal, when abraded by 120 μm SiC papers under identical conditions. The wear resistance of WC-Fe₆₀Al₄₀ composites increased with reduction in WC-grain size and associated with increase in composite hardness. Scanning electron microscopy revealed that the wear surfaces of WC-40% Fe₆₀Al₄₀ composites and WC-Co hardmetal were similar in appearance. The higher hardness and work hardening ability of Fe₆₀Al₄₀ binder, as compared to Co metal, are believed to be responsible for the excellent abrasive wear resistance of WC composites containing iron aluminide binder.     

Some observations on two-body abrasive wear

Pin-on-disc-type two-body abrasion tests were carried out on five metals with seven particle sizes over a range of loads, lengths of travel and sliding speeds. The familiar results that two-body abrasive wear is proportional to load and to distance travelled were confirmed. The “size effect”, in which particles below about 100 μm produce progressively less wear, was shown to be independent of load, sliding speed and prior cold working. Increasing the sliding speed from 1 to about 100 mm s^?1 produced an increase in wear resistance of about 50% for AISI 1020 steel. An increase in velocity above 100 mm s^?1 had little effect on the wear resistance. Plots of the wear resistance against the hardness of the annealed metal showed significant deviations from the linear relationship reported in the literature. The result is influenced by both sliding velocity and particle size.     

Interface Structure and Wear Behavior of Cr26 Ferrous Matrix Surface Composites Reinforced with CTCP

Using cast tungsten carbide particles (CTC_P) and reduced iron powders as raw materials, the porous ceramic preforms with honeycomb, strip, and layer structure, respectively, were prepared by loose sintering process; then, the CTC_P/Cr26 ferrous matrix composites were fabricated by casting infiltration process. The microstructure of the composites was analyzed by SEM, XRD, and EDS. The results show that a sintered shell forms as a result of the reaction of Fe and W₂C in the CTC_P during loose sintering process; the inner part of the shell around the CTC_p consists of WC and Fe₃W₃C phases, while the outer part between the particles is dominated by Fe₃W₃C. Therefore, the strength of preforms is enhanced because the particles are connected with each other by sintered shell. During casting infiltration process, a transition layer constituted by WC and Fe₃W₃C formed at the interface of CTC_p and the matrix due to the dissolution and precipitation of the sintered shell in the high-temperature liquid iron. The three-body abrasive wear behavior of the composites was investigated. The result shows the wear resistance of honeycomb structure composite is comparable to that of whole layer (WL) structure composite, which is three times of heat-treated Cr26. However, the honeycomb structure composite has higher performance/cost ratio owing to the lower CTC_p volume fraction and higher strength and toughness compared with the WL structure composite.     

The abrasive wear resistance of TIC and (Ti,W)C-reinforced Fe–17Mn austenitic steel matrix composites

Pin-on-disc dry sliding wear tests have been carried out to study the wear behaviour of 10 vol% TiC and (Ti,W)C-reinforced Fe–17Mn austenitic steel matrix composites. The composites have been synthesized in situ by means of conventional melting and casting route. It has been observed that the abrasive wear resistance of the composites is higher than that of their unreinforced Fe–17Mn austenitic steel. Compared with the TiC-reinforced composite, the abrasive wear resistance of the (Ti,W)C-reinforced composite is better. The abrasive wear resistance and coefficient of friction of both reinforced and unreinforced materials decrease as the load increases.     

Wear study of Ni–WC composite coating modified with CeO2

In the present investigation, Ni–WC composite powder was modified with the addition of CeO₂ in order to form a new composition of Ni–WC–CeO₂. The Ni–WC and Ni–WC–CeO₂ compositions were used for coating deposition by high-velocity oxy-fuel (HVOF) spraying process so as to study the effect of CeO₂ addition on microstructure, distribution of various elements, hardness, formation of new phases, and abrasive wear behavior. Further, the effect of load, abrasive size, sliding distance, and temperature on abrasive wear behavior of these HVOF-sprayed coatings was investigated by response surface methodology. To investigate the abrasive wear behavior of HVOF-sprayed coatings four factors such as load, abrasive size (size in micrometers), sliding distance (meters), and temperature (°C) with three levels of each factor were investigated. Analysis of variance was carried out to determine the significant factors and interactions. Investigation showed that the load, abrasive size, and sliding distance were the main significant factors while load and abrasive size, load and sliding distance, abrasive size and sliding distance were the main significant interactions. Thus an abrasive wear model was developed in terms of main factors and their significant interactions. The validity of the model was evaluated by conducting experiments under different wear conditions. A comparison of modeled and experimental results showed 4–9% error. The abrasive wear resistance of coatings increases with the addition of CeO₂. This is due to increase in hardness with the addition of CeO₂ in Ni–WC coatings.     

Abrasive wear of cast aluminium alloy-zircon particle composites

The abrasive wear rates of particulate composites of an Al-11.8Si-4Mg alloy containing up to 0.35 volume fraction of zircon particles (average size, 100 μm) were measured on an 80 grit aloxide cloth sheet as a function of the volume fraction of zircon, the applied load and the number of passes over the abrasive paper. When the volume fraction of zircon is above a critical value of 0.09, the abrasive wear resistance (reciprocal of the wear rate) increases with the volume fraction of zircon according to the rule of mixtures. When the volume fraction is fixed, the abrasive wear resistance increases with the number of passes possibly because of blunting of the alumina particles of the abrasive cloth. No improvement in the abrasive wear resistance of composites over the matrix alloy was observed when the volume fraction of zircon was below 0.09. Scanning electron microscopy studies of the abraded surfaces of composites revealed fractured zircon particles but no evidence of filler particle pull-outs or debonding at the interface was obtained.     

WC颗粒增强铁基表面复合材料的三体磨料磨损性能研究

设计、制备了一台三体磨料磨损实验机，对该实验机进行了重现性实验。以高铬铸铁为标样，利用该磨损实验机分别考察了WC颗粒体积分数、载荷与表面复合材料相对耐磨性能之间的关系。实验结果表明：本实验机的测试性能是可靠的；复合材料的三体磨料磨损性能与高铬铸铁标样相比有较明显的提高，在同一载荷下．复合材料的相对耐磨性能随着WC颗粒体积分数的增大呈先升高后降低的变化规律，WC颗粒体积分数为27％的复合材料相对耐磨性最高，达到高铬铸铁的5．12倍；而对于同一种复合材料，随着载荷的增大，其相对耐磨性呈增加趋势，其中WC颗粒体积分数为27％的复合材料增加最为明显；复合材料的三体磨料磨损机理为WC对周围组织的屏蔽作用，失效方式为WC颗粒因疲劳而片状剥落。     

Wear of Ceramic Cutting Tools in Ni-Based Superalloy Machining

The machining performance of monolithic and composite silicon nitride and Al₂O₃-based cutting tools in continuous turning of Inconel 718 was examined. The character of tool wear has been found to vary, depending on the feed rate and cutting speeds. At a lower cutting speed, of 120 m/min, tool life is restricted by depth-of-cut notching, while at high cutting speeds (300 m/min), tools fail due to nose wear and fracture. The sensitivity of monolithic Si₃N₄ and Al₂O₃ to depth-of-cut notching was found to he significantly reduced with the addition of SiC whiskers, and to a lesser extent with TiC particulates. The ceramic composites also exhibited resistance to nose and flank wear that was higher than that of the monoliths. The internal stress distribution for the cutting tool has been calculated using the finite element method and is the basis for explaining fracture beneath the rake face. Cutting tool wear results are discussed in terms of chemical and mechanical properties of the ceramic tool material, abrasive wear, thermal shock resistance, and metal cutting conditions.     

High stress abrasive wear behaviour of aluminium hard particle composites: Effect of experimental parameters, particle size and volume fraction

High stress abrasive wear behaviour of aluminium alloy (ADC-12)–SiC particle reinforced composites has been studied as a function of applied load, reinforcement size and volume fraction, and has been compared with that of the matrix alloy. Two different size ranges (25–50 and 50–80 μm) of SiC particles have been used for synthesizing ADC-12–SiC composite. The volume fraction of SiC particles has been varied in the ranges from 5 to 15 wt%. It has been noted that the abrasive wear rate of the alloy reduced considerably due to addition of SiC particle and the wear rate of composite decreases linearly with increase in SiC content. It has also been noted that the wear resistance of composite varies inversely with square of the reinforcement size. The wear rate of the alloy and composite has been found to be a linear function of applied load but invariant to the abrasive size; at critical abrasive size, transition in wear behaviour is noted. This has been explained through analytically derived equations and wear–surface examination.     

Friction and Wear Properties of ZrO2�CAl2O3 Composite with Three Layered Structure Under Water Lubrication

Zirconia?CAlumina (ZrO₂?CAl₂O₃) composite with three layered structure was prepared, and its friction and wear properties under water lubrication were investigated. The results indicate that the layered composite exhibited better tribological properties comparing with ZrO₂?CAl₂O₃ mono-layered composite at same tested conditions. Good combination of toughness and strength as well as subsequently excellent friction and wear properties were mainly contributed to the residual stress of the layered composite, which caused by thermal mismatch of sintering between layers through special design of compositions and structure. Friction coefficient and wear rate of the layered composite decreased with increment of load and/or velocity. The change of tribological properties was also relative to wear mechanisms, micro-cutting, and abrasive wear were main mechanisms at lower load and/or lower velocity but fatigue wear caused by plastic deformation became dominant at higher load and/or higher velocity.     

Abrasive wear behaviour of B4C particle reinforced Al2024 MMCs

In this study, the effects of volume fraction and particle size of boron carbide on the abrasive wear properties of B₄C particle reinforced aluminium alloy composites have been studied. For this purpose, a block-on-disc abrasion test apparatus was utilized where the samples slid against the abrasive suspension mixture at room conditions. The volume loss, specific wear rate and roughness of the samples have been evaluated. The effects of sliding time, particle content and particle size of B₄C particles on the abrasive wear properties of the composites have been investigated. The dominant wear mechanisms were identified using scanning electron microscopy. The results showed that the specific wear rate of composites decreased with increasing particle volume fraction. Furthermore, the specific wear rate decreased with increasing the size of particle for the composites containing the same amount of B₄C. Hence, it is deduced that aluminium alloy composites reinforced with larger B₄C particles are more effective against the abrasive suspension mixture than those reinforced with smaller B₄C particles.     

The influence of alumina on mechanical and tribological characteristics of graphite particle reinforced hybrid Al-MMC

We consider the influence of alumina (Al₂O₃) particles on mechanical and tribological properties of aluminum hybrid metal matrix composites (MMC). Various weight fraction of Al₂O₃ (5, 10 and 15%) and constant weight fraction of graphite (5%) were used to fabricate composites by stir casting method. The effect of Al₂O₃ content on hardness, density and specific wear rate is evaluated. A wear test was performed using central composite design matrix on a pin-on disc apparatus at room temperature for constant sliding distance of 1000 m. The sliding speed, load and weight fraction of Al₂O₃ were the process variables. The results show that the hardness and density increase with increase in Al₂O₃ content. From the analysis of variance (ANOVA), load is the dominant factor that affects the specific wear rate of hybrid composites followed by speed and weight fraction of Al₂O₃. Based on desirability approach, the improvement in the wear resistance of the composites became more prominent at high speed, high load and high weight fraction of Al₂O₃. The worn surface of the pin was examined using scanning electron microscope (SEM) which indicates that the wear mechanism of composites is mostly abrasive wear followed by oxide wear.