Change In Wear Mechanism Research Articles

Wear performance of laser surface hardened GCr15 steel

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

Comparative Studies on Friction and Wear Performance between Glass-fiber Reinforced Polyamide 66 Composite and Ductile Irons on Ceramic Al2O3 Counterface in Sucker Rod Centralizer Application

The tribological behaviors of three materials for sucker rod centralizer application including glass-fiber reinforced polyamide 66 composite, ductile iron and quenched ductile iron were investigated on the pin-on-disc type wear testing machine against ceramic Al2O3 under both dry sliding and oil field water lubricated conditions. Laser optical microscopy, scanning electron microscopy, Fourier transform infrared spectrometer, digital temperature measurement system and X-ray photoelectron spectroscope were used to investigate the microstructure, wear mechanism and chemical nature change of the studied materials. The results revealed that the coefficients of friction under oil field water lubricated condition were slightly lower than those under dry sliding condition for the studied materials, in which glass-fiber reinforced polyamide 66 composite exhibited the lowest coefficient of friction. The quenched ductile iron showed the lowest wear volume among the studied materials under both dry and lubricating sliding conditions. The wear loss of glass-fiber/polyamide 66 composite was much higher under lubricating condition than that under dry sliding condition, and much higher than those of as-cast and quenched ductile iron, which was attributed to the combination of thermal deformation, degradation and micro-ploughing.

Development of mechanochemical diamond stone containing BaSO4 abrasive

This paper describes a newly developed mechanochemical superabrasive stone containing reactive BaSO4 abrasive. A thermodynamic analysis suggested that BaSO4 reacts with Fe forming oxides. X-ray diffraction patterns revealed that scales that cover steels heated with BaSO4 abrasive consist of Fe3O4, α-Fe and BaS. On the basis of these results, vitrified diamond stones containing BaSO4 abrasive were manufactured and the effect of the BaSO4 abrasive on their performances was evaluated through the superfinishing of bearing steels. It was found that soft BaSO4 abrasive rubs the surface of hardened steel producing smooth surfaces with valleys. The stone reduces both the hardened layer depth and the compressive residual stress in the finished surface because of the formation of a thin white layer. The addition of BaSO4 abrasive improves the wear resistance of diamond stone because the dominant wear mechanism changes from carbon diffusion to oxidization of diamond.

The transition between high and low wear regimes under multidirectional reciprocating sliding

The wear phenomena and wear characteristics of reciprocating sliding wear with superimposed lateral vibrations were investigated using a ball-on-disc tribometer. The tribometer enabled two orthogonal oscillations, whereas one oscillation had a constant amplitude of 1mm (primary oscillation) and the other one had a variable amplitude from 0 to 20.2μm (secondary oscillation). Ball and disc were made of AISI 52100 steel. The ball surface was polished and the disc surface was unidirectionally grinded parallel to the direction of primary oscillation. Two regimes with different wear rates were found, being separated by a characteristic transition amplitude of 2.7±0.4μm in the secondary oscillation. This transition correlated with a change of wear mechanisms from tribochemically to mechanically dominated wear. A wear model based on surface topography and particle motion was developed. The wear model is able to predict the value of the transition amplitude by means of characteristic topographical data and the size of wear particles.

Wear Mechanisms at High Temperatures: Part 2: Temperature Effect on Wear Mechanisms in the Erosion Test

In previous investigations on wear mechanisms at high temperatures made in High Temperature-Single Impact Test (HT-SIT) and High Temperature-Continuous Impact Abrasion Test (HT-CIAT), predominant wear mechanisms were identified and correlations to different material parameters could be presumed. In order to confirm these correlations, four different alloys which are promising to be used in high temperature applications like a sinter grate have been studied in the High Temperature-Erosion Test (HT-ET) by the use of different impact angles and different impact energies. Especially the change of wear mechanism caused by increasing testing temperature was analysed in detail. Characterisation of microstructure and wear behaviour has been done by optical microscopy (OM) and scanning electron microscopy (SEM). Results obtained by the use of the different measurement techniques were linked and set into comparison to calculate the volumetric wear of the specimen. Predominant wear mechanisms were determined using OM in the mode of cross-section images and SEM. The results indicate that material parameters such as hardness and hard phase content can be correlated to the erosion wear rates at different impact angles. The test results indicate that at higher temperatures, the material fatigue becomes a major wear-determining factor. The test results also confirmed that there is a critical impact energy for each material above where the wear rate increases significantly. Test results with thermally aged materials also show that a better heat-resistant matrix reduces the material fatigue thus resulting in lower wear rates.

Polypropylene + Polystyrene Blends with a Compatibilizer. Part 2. Tribological and Mechanical Properties

AbstractStyrene-ethylene/butylene-styrene (SEBS) block copolymer was used as the compatibilizer for PP + PS blends. We have investigated effects of the presence of SEBS on tribological and mechanical properties; dynamic mechanical analysis (DMA) was also performed. Since the copolymer causes formation of smaller particles of the dispersed PS phase in PP matrix blends, there is improved energy transmission and dissipation resulting in higher impact strength. The SEBS additive is relatively soft and causes a decrease in stress at break but an increase in elongation at break in tensile testing. In most cases the friction of the compatibilized blends is higher although in PS-rich blends we find a decrease. Scratch testing shows a change in wear mechanisms when SEBS is added to PP/PS. In uncompatibilized blends we observe adhesive wear, with crazes formed in the middle of the wear track. A compatibilized blend shows more ductile behavior and ploughing wear.

Wear Behaviors of MoSi<sub>2</sub> at Elevated Temperatures

MoSi2 was prepared by SHS, and then pressed under 300 MPa at room temperature and sintered at 1600 °C for 1 h in a vacuum furnace. The tribological properties of MoSi2 against Al2O3 in the temperature range from 700°C to 1100 °C were investigated. Microphotographs and phases of the worn surface of MoSi2 were observed by SEM and XRD. Results showed that MoSi2 has well friction and wear properties below 900 °C. When temperature rises from 900 °C to 1000 °C, wear rate of MoSi2 is raised by 20.8% which is attribute to the change of wear mechanism. The main wear mechanisms of MoSi2 are adhesion and oxidation at high temperatures. When over 900 °C, because of ductile - brittle transition characteristic of this material, plastic deformation and fracture are also found on the worn surface of MoSi2. This leads to the high wear rate of MoSi2.

Wear progression of carbide tool in low-speed end milling of stainless steel

A study was undertaken to investigate the wear of PVD-coated carbide and uncoated carbide tools during milling of STAVAX (modified AISI 420 stainless steel) at low speeds. No significant change in the tool wear was observed when the cutting speed was increased from 25 to 50 m/min. It was found that increasing the hardness of the workpiece from 35 to 55 HRC caused a marked increase in the flank wear and a change in the dominant wear mechanism. In machining STAVAX with a hardness of 35 and 40 HRC, the coated tool was predominantly subjected to abrasive wear throughout the duration of testing. During machining STAVAX with a hardness of 55 HRC with the coated tool, three distinct stages of tool wear occurred, (i) initial wear by abrasion, followed by (ii) cracking and chipping, and (iii) the formation of individual surface fracture at the cracks which would then enlarge and coalesce to form a large fracture surface. The coated tool showed much higher fracture resistance than the uncoated tool. The high fracture resistance exhibited by the coated tool could be attributed to the effectiveness of the coating in preventing the formation of cracks which would act as preferential sites for fracture to take place. The experimental results also show that coating prevents edge chipping and enhances the abrasive wear resistance of the tool. Both the ductility of the workpiece and the tool wear appeared to have influences on the surface finish of the workpiece. It was found that the cutting fluid was effective in preventing catastrophic failure of the tool.

Building Relationship Network for Machine Analysis from Wear Debris Measurements

Integration of system process information obtained through an image processing system with an evolving knowledge database to improve the accuracy and predictability of wear debris analysis is the main focus of the paper. The objective is to automate intelligently the analysis process of wear particle using classification via self-organizing maps. This is achieved using relationship measurements among corresponding attributes of various measurements for wear debris. Finally, visualization technique is proposed that helps the viewer in understanding and utilizing these relationships that enable accurate diagnostics. ICROSCOPIC applications have been one of the important areas in the field of automation for on- line/off-line visual inspection systems in industry and for long-term availability of inventory in warehouses. These systems include analysis of microscopic wear debris. Any change in the steady state operation of the machine creates a change in the normal wear mechanism. This change once transported by a lubricant from wear sites carries important information relating to the condition of engines and other machinery. Researchers have used this information to diagnose wear-producing modes and thus attempt to predict wear failures in machines (1-2). For the purpose of objective diagnosis, the identification and analysis of these wear debris have been reported in literature using various automation techniques. The interested reader is referred to the work of authors in (3-5) for further study. The aim of the overall research has been to develop an image analysis and in some cases knowledge based system to classify wear debris for the objective under study. The authors in (6) have discussed an intelligent expert system via Internet using combination of an expert system and a neural network. The respective authors have only discussed classifications where desired ones are known and corresponding mapping is

Mechanical Properties of 316L Stainless Steel with Nanostructure Surface Layer Induced by Surface Mechanical Attrition Treatment

The mechanical properties of the 316L stainless steel subjected to surface mechanical attrition treatment (SMAT) have been studied, these properties are hardness, tensile properties and wear resistance. The research shows that the thickness of the hardened layer increases with the increasing of the treating time. The refined microstructure in the treated layer led to increasing in hardness, strength, and wear resistance. It is obvious that the surface layer hardness and bulk yield strength are increasing when the SMAT time reaches 5 minutes. The increase of surface layer wear resistance is obvious when the SMAT time is 15 minutes. The SEM observation of the wear scars shows that the nanocrystalline layer might reduce the effect of adhesive wear of 316L stainless steel. Therefore, the wear mechanism changes from adhesive abrasion to grinding particle abrasion after SMAT.

Surface and friction characterization of MoS 2 and WS 2 third body thin films under simulated wheel/rail rolling–sliding contact

The tribological behavior of MoS 2 and WS 2 third body thin films has been studied using thermogravimetric analysis (TGA), high-temperature rheometer (HTR) and an Amsler twin-roller tester that simulates wheel/rail contact in railroad use. These two metal disulfides are found to exhibit lower decomposition temperatures in tribochemical reactions compared to their thermal reactions. The chemical compositions probed by X-ray photoelectron spectroscopy (XPS) show that, under the Amsler rolling–sliding test, both MoS 2 and WS 2 oxidize to the metal trioxide, SO 4 2− and elemental S as solid phase products. These two S-containing products are found exclusively in tribochemical reactions, whereas gaseous SO 2 is the sole product in thermal reactions. This highlights the effect of high pressure as well as micro-slip motion in the contact zone on the decomposition pathways of MoS 2 and WS 2. During the Amsler wear test, the metal disulfide transfer films cover the counter surface as islands of thick patches. Rolling–sliding contact causes a decrease in the population and size of these patches, whose states largely determine the friction coefficient. This gives rise to the typical shape for the Amsler ‘friction curve’, with low/stable friction maintained while the thick patches of friction modifier are present. The conversion of a disulfide to trioxide, which has poorer lubricating properties, modifies the stable friction region and contributes to the slow increase in friction. The wear mechanism and chemical change of the MoS 2 and WS 2 during rolling–sliding are important factors governing the tribological performance in such aspects as friction level, retention time, lubrication regime and failure mode.

Effect of Testing Parameters on Wear Properties of Alumina Strengthen 3Y-TZP Ceramics

The wear behaviours of alumina strengthen 3Y-TZP ceramics worn against high chromium cast iron under various testing conditions were investigated using a block-on-block tribometer. The results showed that the wear rate increases with the increasing of the load and the sliding time. Under the low load the main mechanism governing the wear properties of ceramic is the apparent plastic deformation and ploughing, and the wear rate rapidly increases and the wear mechanism changes into brittle fracture under high load. Meanwhile the wear resistance is depended on the properties of the abrasive particle. As expected, the wear resistance was increased with decreasing hardness of abrasive particle, but it was also influenced by the morphology, that is, the sharper the abrasive particle the higher wear rate.

Enhancement of surface properties of SAE 1020 by chromium plasma immersion recoil implantation

SAE 1020 steel is commonly used as concrete reinforcement and small machine parts, but despite its good mechanical properties, as ductility, hardness and wear resistance, it is susceptible to severe corrosion. It is well known that chromium content above 12% in Fe alloys increases their corrosion resistance. In order to obtain this improvement, we studied the introduction of chromium atoms into the matrix of SAE 1020 steel by recoil implantation process using a plasma immersion ion implantation (PIII) system. Potentiodynamic scans showed that the presence of Cr film leads to a gain in the corrosion potential, from −650mV to −400mV. After PIII treatment, the corrosion potential increased further to −340mV, but the corrosion current density presented no significant change. Vickers microhardness tests showed surface hardness increase of up to about 27% for the treated samples. Auger electron spectroscopy showed that, for a 30nm film, Cr was introduced for about 20nm into the steel matrix. Tribology tests, of pin-on-disk type, showed that friction coefficient of treated samples was reduced by about 50% and a change in wear mechanism, from adhesive to abrasive mode, occurred.

Dry Sliding Wear Behavior of Al 2219/SiCp-Gr Hybrid Metal Matrix Composites

The dry sliding wear behavior of Al 2219 alloy and Al 2219/SiCp/Gr hybrid composites are investigated under similar conditions. The composites are fabricated using the liquid metallurgy technique. The dry sliding wear test is carried out for sliding speeds up to 6 m/s and for normal loads up to 60 N using a pin on disc apparatus. It is found that the addition of SiCp and graphite reinforcements increases the wear resistance of the composites. The wear rate decreases with the increase in SiCp reinforcement content. As speed increases, the wear rate decreases initially and then increases. The wear rate increases with the increase in load. Scanning electron microscopy micrographs of the worn surface are used to predict the nature of the wear mechanism. Abrasion is the principle wear mechanism for the composites at low sliding speeds and loads. At higher loads, the wear mechanism changes to delamination.

Tribological behaviour and residual stress of electrodeposited Ni/Cu multilayer films on stainless steel substrate

In the present study, [Ni (4.5 nm)/Cu ( t Cu = 2, 4 and 8 nm)] multilayers were pulse electrodeposited on stainless steel (AISI SS 304) substrate from sulphate based single bath technique. X-ray diffraction (XRD) was used to investigate the structure and stress of the Ni/Cu multilayer. The results from XRD analysis indicated that the deposited multilayers had a preferred crystal orientation of [111] and presence of satellite reflection suggested the formation of superlattice. The stress level within the deposited multilayers was found to be sensitive to the sublayer thickness. Sliding wear behaviour of electrodeposited Ni/Cu multilayer films has been investigated against a tungsten carbide (WC) ball as the counter body and compared with that of the constituents, Cu and Ni coatings. The wear tests were carried out by using a reciprocating ball-on-flat geometry at translation frequencies of 5 and 10 Hz, slip amplitude of 1 mm and at five different loads of 3, 5, 7, 9 and 11 N. Friction force was recorded on-line during the tests. At the end of the tests, the wear scars were examined by laser surface profilometry and scanning electron microscopy (SEM). Friction coefficient was found to be dependent on load and Cu layer thickness ( t Cu) and the values for multilayers were border between Ni and Cu. Among multilayers, sample with minimum t Cu has shown the lowest friction coefficient and wear rate. With increasing t Cu, the wear mechanism changes from pure abrasive wear at t Cu = 2 nm, to particle entrapment at t Cu = 4 nm to particle embedding at t Cu = 8 nm. Detailed investigation of the wear scar morphology as well as wear rate measurement revealed that at low loads, ( H/ E) ratio and residual stress governed the wear rate and the principle wear mode was abrasive cutting. At intermediate loads, the role of residual stress became insignificant while wear was governed by ( H/ E) ratio and plastic deformation. However, at higher loads, plastic deformation played the major role.

Study on Properties of M50 Steel Implanted With Nitrogen by Plasma-Based Ion Implantation at Elevated Temperatures

M50 steel was implanted with nitrogen at elevated temperatures ranging from 260 degC to 420 degC using plasma-based ion implantation. The effect of implantation temperature on surface microstructure, hardness, and wear resistance was investigated. It is observed that nitrogen penetrates very deeply from the surface as a result of implantation and thermal diffusion at elevated temperatures. The amount of nitrides and their distribution depth as well as the hardness and the wear resistance in the surface layer increase with the processing temperature. As the implantation temperature increases, the wear mechanism changes from adhesive wear to abrasive wear

Adhesive wear behavior of Al xCoCrCuFeNi high-entropy alloys as a function of aluminum content

The Al x CoCrCuFeNi alloys with different aluminum contents prepared by arc melting were investigated on their adhesive wear behaviors. With increasing aluminum content, both the volume fraction of BCC phase and the hardness value increase, and thus the wear coefficient decreases. Moreover, the wear mechanism changes from delamination wear to oxidative wear. For low aluminum content, x = 0.5, the microstructure is of simple ductile FCC phase and the worn surface is deeply grooved and undergoes a periodic delamination which produces big debris. For medium aluminum content, x = 1.0, the microstructure is a mixture of FCC and BCC phases, and the worn surface is deeply grooved in FCC region but smooth in BCC region. Delamination wear is still dominant although oxidative wear occurs in the smooth region. For high aluminum content, x = 2.0, the microstructure is of BCC phase and the worn surface is smooth and yields fine debris with high oxygen content. The high aluminum content gives a large improvement in wear resistance. This improvement is attributed to its high hardness, which not only resists plastic deformation and delamination, but also brings about the oxidative wear in which oxide film could assist the wear resistance.

Effect of machining parameters and coating on wear mechanisms in dry drilling of aluminium alloys

The temperature generated by friction and plastic deformation in the secondary shear zone strongly controls tool wear. At lower cutting speeds tool wear is not severe insofar as the temperature is not significant. When the cutting speed is increased, there is a transition in wear mechanisms from abrasion and/or adhesion to diffusion. In the present paper, the change in wear mechanisms as a function of cutting speed and coating material is discussed. The cutting tests were performed on a rigid instrumented drilling bench without the use of cutting fluids. AA2024 aluminium alloy was used to investigate the wear mechanisms of cemented tungsten carbide and HSS tools. Three cutting speeds (25, 65 and 165 m/min) and a constant feed rate of 0.04 mm/rev were selected for the experiments. The best results in terms of maximum and minimum hole diameter deviations and surface roughness are obtained for the uncoated and coated tungsten carbide drills. The results also show that HSS tool is not suitable for dry machining of AA2024 aluminium alloy.

Wear Mechanism of Nano-Structured Surface Layer under High Impact Energy

Under high impact energy, nano-structured surface layers of Hadfield steel and annealed AISI 1045 steel were investigated in the present paper. It has been observed that a so-called “black layer” for Hadfield steel and “white layer” for AISI 1045 steel has been formed, respectively. That definitely will give rise to a change of wear mechanism. The wear tests showed that the wear weight loss curve of Hadfield steel will be bent down after some critical impact numbers. The wear curve of the AISI 1045 steel, however, shows a step-like characteristic with increasing impact numbers. It can be found from microstructural examination that high density twin bands of subsurface for Hadfield steel were produced, which have good plastic deformation coordination with bulk material. Cracks are usually initiated in the “black layer” underneath 12 µm in depth, and the worn debris sizes were also observed in nano-scale. Nano scaled wear controls the whole wear process. For the annealed AISI 1045 steel, cracks are mainly initiated between the interface of the “white layer” and sub-surface deformation layer. Debris is in micron-scale and spalled in the flake-like style. The wear weight loss is, therefore, greater than that of Hadfield steel. The result showed from the wear tests of Hadfield steel and AISI 1045 steel that nanocrystalized process of subsurface becomes one of control factors to affect wear losses and wear mechanism under high impact energy.

Wear Analysis of Head-Disk Interface During Contact

To achieve a higher storage density in a hard disk drive, the fly height of the air bearing slider, as part of the magnetic spacing, has to be minimized. At an ultralow fly height, the intermittent–continuous contact at the head–disk interface (HDI) is unavoidable and directly affects the mechanical and magnetic performance of the hard disk drive, and is of great interest. The HDI wear has a nonlinear and time-varying nature due to the change of contact force and roughness. To predict the HDI wear evolution, an iterative model of Coupled Head And Disk (CHAD) wear, is developed based on the contact mechanics. In this model, a composite transient wear coefficient is adopted and multiple phases of the wear evolution are established. A comprehensive contact stiffness is derived to characterize the contact at the HDI. The abrasive and adhesive wear is calculated based on the extended Archard’s wear law. The plastic and elastic contact areas are calculated with a three-dimensional (3D) sliding contact model. Based on the CHAD wear model, for the first time, the coupling between head and disk wear evolutions is thoroughly investigated. Accelerated wear tests have also been performed to verify the disk wear effect on the slider wear. A wear coefficient drop with time is observed during the tests and it is attributed to a wear mechanism shift from abrasive to adhesive wear. A shift in the type of contact from plastic to elastic accounts for the wear mechanism change.