Wear Behavior Of Materials Research Articles

Tribological Properties of Carbon Fiber Epoxy Resin Composite and Polyimide Material at High and Low Temperatures

Carbon fiber epoxy resin composite and polyimide material are likely to be applied to pulley-guideway system of the new satellite antenna. Their tribological properties have effects on the motion characteristics of the pulley-guideway system. To master the tribological properties of carbon fiber epoxy resin composite and polyimide material, this paper carries out tests of tribological properties and wear behavior of carbon fiber epoxy resin composite and polyimide material at 130°C and 30°C. Carbon fiber epoxy resin composite is used as the grinding specimen and polyimide material is used as the counter-grinding specimen. Tribological properties of this material pairs is studied under diverse linear velocity and external loads. The results show that friction coefficient of this material pairs is stable under different conditions, especially at 30°C. Meanwhile, wear behavior of this material pairs is mainly affected by ploughing of surface roughness at low temperature, while by surface micro-spalling at high temperature.

Impact-sliding wear behaviors of 304SS influenced by different impact kinetic energy and sliding velocity

Abstract Wear behaviors of materials in nuclear power stations are very complex, because they are rarely subject to just pure impact or sliding wear. This study uses a self-made impact-sliding wear test rig to study the influences of impact kinetic energy and sliding velocity on the energy absorption, mechanical response, interface deformation, and damage behavior of nuclear-grade 304 stainless steels (304SS). The results show that an increase in impact velocity causes an increase in absorbed energy, impact force, and friction force, while lowing the friction coefficient. The friction force and friction coefficient increase with an increase in the sliding velocity, whereas no obvious change is seen in impact force and absorbed energy. The dominant wear mechanism in test samples were delamination failure and friction oxidation. Furthermore, numerical study was performed to explain the effect of velocity on the mechanical response of 304SS.

Effect of Speed on Tribological Properties of Graphene Toughned Alumina (Al-G) Composite

This research work discusses the influence of different wt% of Graphene addition to Alumina matrix and its impact on mechanical properties such as hardness and wear properties of prepared composites (Al-G). The Al-G composites were prepared using powder metallurgy technique with the help of microwave sintering. The hardness of prepared specimens was tested using the Vickers hardness test for various combinations of Graphene in alumina matrix. The wear behaviour of material is explored using Pin on disk apparatus at various speeds and sliding distances for different wt% of graphene added alumina samples. The weight percentages of graphene vary from 0.1 to 0.4wt% with the interval of 0.1%. It was observed that the presence of graphene in alumina and processed with microwave sintering has a significant effect on wear properties of the Al-G composite. The present work focussed on the improvement in wear resistance through microwave sintering of alumina with the addition of various wt% of graphene. The main aim is to explore best optimum AL-G composition for increased wear resistance.

Tribological Performance of PTFE Filled with 40% Bronze against Different Surface Textured Patterns

PTFE, a thermoplastic polymer is having low friction coefficient, excellent corrosion resistance, chemical inertness and wide range of service temperature. Due to its poor wear and abrasion resistance, its applications are widely limited. The wear resistance of PTFE can be significantly improved by addition of suitable filler material. Bronze filled PTFE composites produces very thick, uniform and adherent transfer films of both PTFE and Bronze. Surface Texturing is a phenomenon to reduce contact area between two mating surfaces which affects friction and wear behaviour of material. Therefore, in this research, the friction and wear behaviour of PTFE composite filled with 40% Bronze particles at varying load and sliding velocity was studied. Test pins of PTFE composite were tested against textured stainless steel disc under dry and wet sliding conditions using Pin-On –Disc tribometer (TR-20LE) at NTP. There were three types of textured patterns made on the disc i.e. circular, elliptical and square. It was observed that the total wear loss due to friction and wear increases with increase in load as well as increase in sliding velocity. The lowest wear loss was found for PTFE composite filled with 40% Bronze, when circular textured pattern was used under wet sliding condition.

Effect of Humidity on Friction and Wear—A Critical Review

The friction and wear behavior of materials are not intrinsic properties, but extrinsic properties; in other words, they can drastically vary depending on test and environmental conditions. In ambient air, humidity is one such extrinsic parameter. This paper reviews the effects of humidity on macro- and nano-scale friction and wear of various types of materials. The materials included in this review are graphite and graphene, diamond-like carbon (DLC) films, ultrananocrystalline diamond (UNCD), transition metal dichalcogenides (TMDs), hexagonal boron nitride (h-BN), boric acid, silicon, silicon oxide, silicates, advanced ceramics, and metals. Details of underlying mechanisms governing friction and wear behaviors vary depending on materials and humidity; nonetheless, a comparison of various material cases revealed an overarching trend. Tribochemical reactions between the tribo-materials and the adsorbed water molecules play significant roles; such reactions can occur at defect sites in the case of two-dimensionally layered materials and carbon-based materials, or even on low energy surfaces in the case of metals and oxide materials. It is extremely important to consider the effects of adsorbed water layer thickness and structure for a full understanding of tribological properties of materials in ambient air.

Material Characterization and Influence of Sliding Speed and Pressure on Friction and Wear Behavior of Self-Lubricating Bearing Materials for Hydropower Applications

Nowadays, hydropower plants are forced to have more frequent power control and the self-lubricated bearings used in the applications are one of the most critical components affected by the continuously changing operating conditions. In this study, microstructure and composition of two commercially available bearing materials (Orkot TXM Marine and Thordon ThorPlas) used in hydropower turbines were studied. In addition, the influence of sliding speed and applied pressure on the friction and wear behavior of the materials was investigated systematically for dry sliding conditions. The bearing materials were characterized using X-ray microtomography, Nuclear Magnetic Resonance (NMR) spectroscopy and Inductively Coupled Plasma–Sector Field Mass Spectrometry (ICP-SFMS) techniques. Friction and wear tests were carried out with a polymer pin sliding against a stainless steel (SS2333) plate with a linear reciprocating motion. Test conditions were: room temperature, 9–28 MPa pressure and 10–40 mm/s sliding speed ranges. Surface analysis of the polymer pins and the wear tracks were performed by optical profilometry, Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS) techniques. Test results show that, for both materials, the coefficient of friction (COF) is decreasing at higher pressures. Surface analysis reveals higher concentrations of solid lubricants in the transfer layers formed at higher pressures, explaining the decrease in COF. Furthermore, the specific wear rate coefficients are increasing at higher sliding speeds, especially at lower pressures. Results of this study demonstrate that, under dry sliding conditions, changes in sliding speed and pressure have a significant influence on the tribological behavior of these bearing materials.

Pathways of Dissipation of Frictional Energy under Boundary Lubricated Sliding Wear of Martensitic Materials

The challenges of technical systems subjected to friction and wear become more demanding with steadily increasing stresses. Besides safety matters, failure of tribologically loaded systems can cause tremendous maintenance costs. Because of the lack of a general wear prediction model, tribometer tests must be used in order to investigate wear behaviour of materials in certain tribological systems. Any well-aimed optimizations of tribological contacts requires a comprehensive understanding of friction and wear mechanisms. Otherwise the transferability into technical applications is questionable because of the wide range of applied loads, lubrication conditions, and materials microstructures. In this study, specimens with different topographies and subsurface microstructures were investigated prior to and after tribological testing. The analyses of surface and subsurface characteristics were performed by means of complementary high-resolution electron-microscopy techniques. The study attempted to link the findings to the wear behavior in order to gain information about the pathways of dissipation and transformation of frictional energy into wear. It was found that the dissipation pathways of base body and counter body were different, resulting in diverse tribological behaviour. Nonetheless, the presence of a near-surface grain-refined layers (tribomaterial) supported by a sub-surface strain gradient appears to provide a beneficial influence. Despite the fact that any direct or even conclusive relation to the topographies or subsurface microstructures cannot be given, the discussion provides some hints on how to analyse such systems for their characteristic mechanisms. In addition to the capability of such approach as one step of understanding, its limitations are shown and briefly discussed as well.

Aging effect of pH on the mechanical and tribological properties of dental composite resins

ABSTRACTThis study evaluated the microhardness and wear behavior alterations of dental resins exposed to strong acid and alkaline degradation regimens. Fifty specimens of AP-X, Z350, P60, VITA ZETA and VITA LC resins were distributed into 10 groups. The control group was not subjected to aging treatment, while the other nine groups were assigned to the following pH solutions: 1, 7 or 13 for 1, 13 or 20 d, respectively. Vickers microhardness and wear behavior of materials without aging served as the reference. Repeated measurements were conducted for other specimens. Scanning electron microscopy was used to observe the morphology. Data were analyzed by repeated-measures one-way ANOVA, followed by the least significant difference (LSD) t-test (P ≤ 0.05) for multiple comparisons. The aging process was aggravated over time. Alkaline medium significantly decreased the microhardness and wear resistance of resins, and led to serious surface damage. AP-X, P60 and Z350 immersed in different media showed a lower degradation than the nanoresin. The mechanical degradation of resin composites was aggravated with increased aging time. Strong alkaline media induced the largest reduction in mechanical and tribological properties. Hybrid resin composites with high filler loading exhibited better mechanical performance than nanoresins with low filler loading under different pH conditions.

Effect of nanoparticles on mechanical and tribological properties of composite friction materials

Wear mechanism of newly developed asbestos-free frictional materials (i.e. brake pads material) was investigated by physical-mechanical experiments. The suitability of the developed these new composite materials were investigaed by firiction testes at the different temperatures. Thermal investigation was performed by a differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Stability and mechanical properties at different temperatures of the brake pad materials were comparatively evaluated. Testing results showed that under the given conditions, new developed frictional material has the advantages of the good tribological properties over the widely used commercial asbestos enhanced material as a FK-24A (Retinax, mark B). The research of the thermal and wear behaviour of materials indicates that brake pair has better frictional characteristics and wear resistance performance at high temperature. With use of new friction brake pads materials will be improved the safety of braking processes, and the quality in drilling will be increased. There is also an environmental and economic advantages in using the new asbestos-free materials in the break pads.

Reprint of ‘‘Computational study of the particle size effect on a jet erosion wear device’’

Computational fluid dynamics (CFD) is a useful tool to predict the erosion behaviour over geometries exposed to conditions of severe erosion wear. This work shows how CFD can be used to virtually characterize the wear behaviour of materials used in several hydraulic components, including turbomachinery systems, in which it is important to consider the effect of particle size. In addition, this work develops a methodology for determination and validation of the constants involved in the well-known Tabakoff-Grant model for erosion prediction using the erosion wear obtained via erosion testing in a jet tribometer reported in the literature as a reference. From the experimental data, an optimization algorithm was performed to determine the optimal values of Tabakoff-Grant model constants for ASTM A743 grade CA6NM martensitic stainless steel. The simulated erosion rate agrees with the experimental data for the material analysed in jet erosion simulations with impact angles ranging from 15° to 90°. The change of the angle of maximum erosion rate for small particles, which has been reported in the literature via experimentation, was explained satisfactorily. The results showed that the erosion rate with smaller particles is affected by fluid flow, since small particles tend to follow the flow streamlines, while larger particles move according to the conditions imposed by the jet at its outlet. The effective impingement angle against the surface for small particles is lower than the impingement angle for large particles; therefore, the angle of maximum erosion rate, measured between the jet and the sample's surface, for small particles increases.

Computational study of the particle size effect on a jet erosion wear device

Computational fluid dynamics (CFD) is a useful tool to predict the erosion behaviour over geometries exposed to conditions of severe erosion wear. This work shows how CFD can be used to virtually characterize the wear behaviour of materials used in several hydraulic components, including turbomachinery systems, in which it is important to consider the effect of particle size. In addition, this work develops a methodology for determination and validation of the constants involved in the well-known Tabakoff-Grant model for erosion prediction using the erosion wear obtained via erosion testing in a jet tribometer reported in the literature as a reference. From the experimental data, an optimization algorithm was performed to determine the optimal values of Tabakoff-Grant model constants for ASTM A743 grade CA6NM martensitic stainless steel. The simulated erosion rate agrees with the experimental data for the material analysed in jet erosion simulations with impact angles ranging from 15° to 90°. The change of the angle of maximum erosion rate for small particles, which has been reported in the literature via experimentation, was explained satisfactorily. The results showed that the erosion rate with smaller particles is affected by fluid flow, since small particles tend to follow the flow streamlines, while larger particles move according to the conditions imposed by the jet at its outlet. The effective impingement angle against the surface for small particles is lower than the impingement angle for large particles; therefore, the angle of maximum erosion rate, measured between the jet and the sample's surface, for small particles increases.

Wear behavior of asbestos-free eco-friendly composites for automobile brake materials

Abstract The goal of this work is to study the wear behavior of materials that have the potential to be used as brake pad materials under different contact loads and speeds instead of asbestos. The three different brake pad materials studied are flax fiber reinforced phenolic composites (FFRC), basalt fiber reinforced phenolic composites (BFRC), and flax/basalt reinforced hybrid phenolic composites (HFRC). A wear mechanism map was developed by using the fuzzy c-means clustering algorithm method (FCM) to study the wear mechanism of composites. The results showed BFRC to be a better brake pad material than the other fiber reinforced composites studied, because the good thermal characteristics and bonding nature of basalt fiber increased the wear resistance of BFRC considerably.

Friction and lifetime of a contact lubricated by a solid third body formed from an MoS1.6 coating at low temperature

A special test device has been designed to investigate the friction and wear behaviour of materials under very low temperature conditions. This paper describes an analysis of friction and wear in sliding contacts “lubricated” by a solid third body formed in situ from a non-stoichiometric MoS1.6 coating at 297K, 223K, 173K and 123K, under reciprocating kinematics in a gaseous atmosphere. It was found that under given test conditions, the friction coefficient was somewhat higher at low temperature than at room temperature under oxidising atmosphere. The lifetime was ten times lower at 123K than at room temperature. Under no oxidising atmosphere the temperature does not effect on the friction value. The consequences of decreasing temperature on friction and lifetime are interpreted on the basis of experimental evidence and from the viewpoint of mechanics in order to evaluate third body flows and the rheology activated in the contact.

Wear behavior and work hardening of high strength steels in high stress abrasion

High strength steels (HSS) used in highly abrasive environments, such as in mining and crushing, must endure high stress abrasion. To properly understand the wear behavior of materials under such circumstances, the connection between surface loading, work hardening, and material removal has first to be determined. In this study, wear resistant steels with initial hardness ranging from 400 to 750 HV were investigated in single-grit abrasion. In the cyclic abrasion experiments, the abrasion resistance of the steels was improved noticeably from the initial state due to surface hardening. However, the highest surface hardening rate did not result in the highest wear resistance. Moreover, when the surface loading was sufficiently increased, the transition to a high wear rate mechanism was observed.

WEAR BEHAVIOR OF STEPPED AUSTEMPERED DUCTILE IRON BALLS IN GRINDING IRON ORE

In the present study, an attempt has been made to evaluate the suitability of austempered ductile iron as grinding media material for grinding the iron ore in a ball mill. They are austenitised at 920 0 C for 60 minutes and given stepped austempering heat treatment: 400 0 C for 15, 30, 45, and 60 minutes followed by 300 0 C for 120 minutes for each case. Grinding wear behaviour of these materials are assessed for wear loss in wet condition. The grinding operation are carried out for 60 minutes at 60 % pulp density under closed mill conditions .The pH of mineral slurry is varied from 7 to 10.5 pH to assess the influence of pH on grinding wear behavior of ball material. It is found that wear rate of grinding media material increases proportionally with decrease in pH. These wear rate values are compared with En-31 forged steel under similar conditions. It is found that wear resistance of stepped austempered ductile iron is superior compared to En-31 forged steel balls for wet condition.

Adolf Martens and his contribution to materials engineering

Adolf Martens (1850–1914) was a pioneer of materials engineering. After his studies in Berlin he joined a railway company being responsible for the technical equipment. His interest for the basic mechanisms of mechanical strength and fracture of metallic materials led him to the development of the basic concepts for metallography; his papers published between 1878 and 1889 laid the fundament of this technique. In 1880 Martens changed to the Royal Industrial Academy in Berlin and by 1884 he was designated as director of the Materials Testing Laboratory at the Technical University Berlin. Under his guidance this institution acquired an excellent reputation in all relevant areas of the German industry, forming the nucleus of the Bundesanstalt für Materialforschung und – prüfung (BAM) – the Federal Institute for Materials Research and Testing. Martens developed equipment in many different areas as mechanical testing of metallic materials and of paper, characterization of the wear behavior of materials and viscosity of lubricants. His overwhelming contribution to materials engineering was recognized as early as 1895 by Floris Osmond, who denominated martensite a metallographical constituent resulting from quenching of steels. In 2000 ISO designated the value obtained from the instrumented indentation method as Martens Hardness – HM.

A new method to investigate the sliding wear behaviour of materials based on energy dissipation: W–25wt%Cu composite

Abstract A new method is proposed to explain and monitor wear behaviour based on energy dissipation. The wear of a W–25 wt%Cu composite against 52100 steel was used to demonstrate this approach with pin-on-disc tests conducted under three normal loads. An energy-dependent criterion, namely, specific wear volume (wear volume/dissipated energy (mm 3 /J)), was defined to evaluate the wear of the composite. The s pecific wear volume can be used as a substitute for the traditional wear rate due to the simultaneous expression of several wear parameters and because of its strong dependence on the wear mode. The s pecific wear volume appears to be constant in any particular “wear mode” regardless of the active “wear processes”. In the wear of this composite, processes such as particle pull-out, mechanically mixed layer (MML) formation, crack propagation and delamination were observed. But, combination of these processes in each test had identical specific wear volumes . Thus, all of these wear processes were considered to be consecutive stages of the same wear mode: fatigue wear. The amount of dissipated energy and the volumetric loss increased with increasing normal load. Also, changing the normal load changed the rate of energy dissipation per unit sliding distance.

Application and conceptual explanation of an energy-based approach for the modelling and prediction of sliding wear

Abstract Establishing an accurate predictive model for wear will result in major improvements in the efficiency, lifetime, cost and performance of many engineering systems. The authors have previously proposed a practical energy-based model to describe the tribological damage using energy dissipation. In this work, the capacity of this method to simplify the complex wear phenomenon was determined, and the applicability of this method to forecast the wear behaviour of materials was investigated. The wear results for a W–Cu electrical contact composite were utilised to determine the practical value of the model. Numerical integration of friction force–distance diagrams was used to evaluate the energy dissipation. Linear and non-linear least squares methods were applied to find the optimal curve fitting. It is shown that this model can be applied in two general forms: (1) a graphical method and (2) an explicit formulation. Both of these forms are shown to be capable of providing the necessary information, based on a limited number of initial tests, to predict unknown wear data (volume loss, lifetime, energy) without the need for morphological observations.

Abrasive wear behaviour of conventional and large-particle tungsten carbide-based cermet coatings as a function of abrasive size and type

Abrasive wear behaviour of materials can be assessed using a wide variety of testing methods, and the relative performance of materials will tend to depend upon the testing procedure employed. In this work, two cermet type coatings have been examined, namely (i) a conventional tungsten carbide-cobalt thermally sprayed coating with a carbide size of between ∼0.3–5 μm and (ii) a tungsten carbide-nickel alloy weld overlay with large spherical carbides of the order of ∼50–140 μm in diameter (DuraStell). The wear behaviour of these two materials has been examined by the use of two abrasion tests, namely the micro-scale abrasion test using both silica and alumina abrasives (typically 2-10 μm in size), and the dry sand-rubber wheel test (ASTM G65), again with both silica and alumina abrasives (typically 180–300 μm in size). It was found that when the abrasive particles were of the same scale or larger than the mean free path between the hard phase particles, then the matrix phase was well protected by the hard phases. Testing (in both test types) with alumina abrasives resulted in wear of both the hard carbide phases and the matrix phases in both the thermally sprayed coating and the weld overlay, with the thermally sprayed coating exhibiting lower wear rates. The wear behaviour of the materials with the more industrially relevant silica abrasive was more complex; the thermally sprayed coating exhibited a lower wear rate than the weld overlay with the fine abrasive in the micro-scale abrasion test due to effective shielding of the matrix from abrasive action due to the fine reinforcement particle size. In contrast, with the coarser silica abrasive in the dry sand-rubber wheel test, the weld overlay with the large carbides was able to provide matrix protection with low rates of wear, whereas the thermally sprayed coating wore by fracture of the more brittle microstructure. These findings demonstrate the importance of selection of appropriate laboratory test procedures and abrasives to simulate behaviour of materials in service environments.

Characterisation and Tribological Investigation on Thermally Processed Nanostructured Fe-Based and Cu-Based Cermet Materials

The feasibility of achieving a nanostructured material after different thermal processing of nanosized powders is presented. The thermal processing was done by either atmospheric plasma spraying, laser sintering, or extrusion followed by hot isostatic pressing. The structural characterisation of such thermally processed nanostructured Fe-based and Cu-based metallic or Al2O3 reinforced cermets, confirmed the retention of a nanostructure after each of these thermal processes. Hardness measurements confirmed an increased hardness as expected in the case that nanostructuring is achieved. The role of grain boundaries and second phase particles on the retention of the nanostructure after thermal processing is discussed. Finally, the possible benefit of nanostructuring on the friction and wear behaviour of materials in sliding tests against corundum in ambient air is reported and discussed.