Two-body Abrasion Research Articles

Overlay materials used for increasing lifetime of machine parts working under conditions of intensive abrasion

We evaluated a degree of the machine part abrasive wear with secondary focus on their hardness. The paper states laboratory results of overlay systems from their wear resistance point of view. Laboratory experiments were carried out by two-body abrasion on bonded abrasive of a P120 granularity. The results proved an increased abrasive wear resistance of martensitic, ledeburitic and stellitic overlays against eleven different original products. The overlay UTP Ledurit 60 reached the optimum values. The GD-OES (Glow Discharge Optical Emission Spectroscopy) method proved the different chemical composition of the overlay from the stated chemical composition of the overlaying electrode.    

Investigation on tribological behaviour of diesel engine exhaust valve dry sliding against valve seat

A high-chromium alloy with 2Cr32Si2MnMo2 available for diesel engine valve seats was fabricated by centrifugal casting to improve valve seat quality. The friction and wear performances of the valve seat dry sliding against an exhaust valve were measured using a SRV testing machine. The test procedures include temperature and load sensitivities and wear. The test temperatures ranged from 100 ℃ to 280 ℃ and loads from 50 to 125 N. The friction and wear of the valve seat were found to decrease first and then increase with the increment of temperature or load. Scanning electron microscopy and energy dispersive X-ray spectroscopy analyses revealed the tribofilms contained more friction-increasing Cr2O3 and the wear mechanism was a complicated combination of two-body abrasion, three-body abrasion and oxidation. The strong adhesion between the valve and its seat arrested the relative sliding, but with loads going up to 150 N. In most cases, the valve had unexpectedly higher wear resistance than that of its seat over the temperature range, which is ascribed to adhesion to the tribofilms.

Development of a two-body wet abrasion test method with attention to the effects of reused abradant

A simple test method has been developed to quantify the response of metals and alloys to two-body wet abrasion. A metallographic polishing machine was modified to create a disk-on-flat sliding test rig. Adhesive-backed SiC grinding papers were used under fixed load and speed to rank the abrasive wear of seven alloy steels, some of which are candidates for drill cones for geothermal drilling. Standardized two-body abrasion tests, like those described in ASTM G132, feed unused abrasive into the contact; however, the current work investigated whether useful rankings could still be obtained with a simpler testing configuration in which specimens repeatedly slide on the same wear path under water-lubricated conditions. Tests using abrasive grit sizes of 120 and 180 resulted in the same relative ranking of the alloys although the coarser grit produced more total wear. Wear decreased when the same abrasive disk was re-used for up to five runs, but the relative rankings of the steels remained the same. This procedure was presented to ASTM Committee G2 on Wear and Erosion as a potential standard test for wet two-body abrasive wear.

Reinforcements affect mechanical properties and wear behaviors of WC clad layer by gas tungsten arc welding

This work deals with the surface analysis, mechanical properties and wear performances of the clad layer, which is made from tungsten carbide (WC) powders on SKD61 die steel by the gas tungsten arc welding method. According to the experimental results, due to the high hardness and elastic modulus reinforcements (Fe3W3C and M7C3) existing in the WC clad layer, the WC clad specimen has excellent wear performance at different sliding speeds.According to the wear analysis, wear behaviors of the WC clad layer are two-body abrasion and oxidation wear. In addition, oxidation wear dominates the wear behaviors of the SKD61 die steel specimen at different sliding speeds.

Improvement of Abrasion Wear Resistance of Ductile Iron by Two-Step Austempering

Abrasion wear rates of conventional and two-step austempered ductile cast iron (ADI) were investigated. Conventional austempering and two-step austempering processes were carried out at 280, 300, and 320°C. Microstructures revealed that higher austemperig temperature resulted in coarser ausferrite and higher volume fractions of blocky retained austenite. The ausferrite in two-step austempered ADI was slightly coarser comparing to the coventional ADI since the temperature was raised by 30°C during austempering. Two-body abrasion wear rates of ADIs were studied using a Suga abrasion wear tester. It was found wear rates of the two-step ADI become significantly lower than those of the conventional ADI, especially when the austempering was carried out at low temperature, i.e. 280°C. Such behavior was due to the strong influence of high carbon concentration in retained austenite eventhough the ausferrite matrix was coarser.

Sliding and Abrasive Wear Behavior of WC-CoCr Coatings with Different Carbide Sizes

This study examines the sliding and abrasive wear behaviors of high-velocity oxy-fuel (HVOF)-sprayed WC-CoCr coatings with different WC grain sizes. The HVOF coating deposition was assisted by in-flight particle temperature and velocity measurement system. The powder feedstocks and their corresponding coatings were characterized by means of XRD and Field Emission Scanning Electron Microscope analysis. Hardness, porosity, and indentation fracture toughness of these coatings were calculated and compared with each other. Sliding wear resistance of these coatings was calculated using pin-on-disk tribometer (ASTM G99-90). The two-body abrasion was quantified by sliding the samples over silicon carbide (SiC) abrasive paper bonded to a rotating flat disk of auto-polisher. The mechanism of materials' removal in both the sliding and abrasive wears was studied and discussed on microstructural investigations. It was observed that fine grain WC-CoCr cermet coating exhibits higher sliding and abrasive wear resistances as compared with conventional cermet coating.

Effect of Nitro-Carburizing Treatment on Wear Mechanism and Friction of Steel/WC-Co Sliding Couple

In this work, tribological behavior and material degradation mechanisms of Nitro-carburized AISI H11 hot work tool steel were investigated during sliding against cemented tungsten carbide (WC/Co). The diffusion layer with an iron-nitrocarbide (Fe (N,C)) compound layer was developed on pre-hardened tool steel by a low temperature Ferritic Nitro-Carburizing (FNC) process in a gas medium. The X-ray diffraction analysis, microhardness testing, and optical microscopy were employed to indicate the properties of the compound and diffusion layers. Friction and wear tests were carried out by using the pin-on-disk technique under severe wear condition, and a wear map was provided for different load and sliding distance. Results of SEM secondary and backscatter imaging of wear scar together with EDS analysis of wear debris showed insignificant two-body abrasion wear system and oxide tribo-film on the nitro-carburized samples. In the case of the hardened sample, intensive plastic deformation on the surface, adhesion, and disk materials transfer developed three-body abrasive wear and a degradation mechanism. It was concluded that a lower material degradation rate and the friction coefficient of nitro-carburized steel in comparison with the hardened sample can be related to the formation of a protective oxide layer and a gradual increase in hardness from surface to substrate.

Investigations on Microstructures and Two-body Abrasive Wear Behavior of Fe–B Cast Alloy

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.

An investigation of the effect of work piece reinforcing percentage on the machinability of Al-SiC metal matrix composites

This paper presents the study of the tool wear mechanism in machining the metal matrix composites (MMC) and its dependence on the percentage of reinforcing with MMC. Aluminum alloy (A356 - SiC) silicon carbide metal matrix composite of two samples, were prepared in-house by using stir casting method. Samples having 10 and 20% silicon carbide particles (grain size ranging from 55 to 85 mm) by weight are fabricated in the form of cylindrical bars. Experiments were conducted in the medium duty lathe by using polycrystalline diamond (PCD) insert. Optimum parameters were obtained by analyzing the power consumed on an average surface roughness (Ra) of the machined component. By setting these optimum parameters at a constant machining condition, tool wear study was carried out for a time duration of 100 min. The result showed that the tool flank wears was maximum while machining 20% of the SiC reinforcing MMC when compared with 10% of the SiC reinforcing MMC. The result proved that the influence of SiC particles’ weight percentage was a dependent parameter on tool wear. The main mechanism of tool wear in machining Al-SiC MMC includes two-body abrasion and three-body abrasion. However, the tool wear images were captured by optical microscope and SEM, which supported the result. Key words: Machining, PCD, Al-SiC-MMC, different percentage of SiC reinforcing, power consumed, tool wear.

The effect of anisotropicity of Norway spruce (Picea abies) during two-body abrasion

The effect of anisotropicity of Norway spruce (Picea abies) during two-body abrasive wear was investigated by rubbing the wood with five different orientations while using constant surface pressure and a sanding belt with very fine abrasive grits. The anisotropic nature was found to affect the microstructure of the worn surface and the breakage mechanism of the surface. The properties of the particles that were released from the surface during abrasion were dependent on the grinding orientation and if the particle originated from early- or latewood. The wear process was influenced by the anisotropic nature of wood.

Validation of proposed metrics for two-body abrasion scratch test analysis standards

The objective of this work was to evaluate a set of standardized metrics proposed for characterizing a surface that has been scratched from a two-body abrasion test. This is achieved by defining a new abrasion region termed Zone of Interaction (ZOI). The ZOI describes the full surface profile of all peaks and valleys, rather than just measuring a scratch width as currently defined by the ASTM G 171 Standard. The ZOI has been found to be at least twice the size of a standard width measurement, in some cases considerably greater, indicating that at least half of the disturbed surface area would be neglected without this insight. The ZOI is used to calculate a more robust data set of volume measurements that can be used to computationally reconstruct a resultant profile for detailed analysis. Documenting additional changes to various surface roughness parameters also allows key material attributes of importance to ultimate design applications to be quantified, such as depth of penetration and final abraded surface roughness. Data are presented to show that different combinations of scratch tips and abraded materials can actually yield the same scratch width, but result in different volume displacement or removal measurements and therefore, the ZOI method is more discriminating than the ASTM method scratch width. Furthermore, by investigating the use of custom scratch tips for our specific needs, the usefulness of having an abrasion metric that can measure the displaced volume in this standardized manner, and not just by scratch width alone, is reinforced. This benefit is made apparent when a tip creates an intricate contour having multiple peaks and valleys within a single scratch. This work lays the foundation for updating scratch measurement standards to improve modeling and characterization of three-body abrasion test results.

Standardization of a volumetric displacement measurement for two-body abrasion scratch test data analysis

A limitation has been identified in the existing test standards used for making controlled, two-body abrasion scratch measurements based solely on the width of the resultant score on the surface of the material. A new, more robust method is proposed for analyzing a surface scratch that takes into account the full three-dimensional profile of the displaced material. To accomplish this, a set of four volume- displacement metrics was systematically defined by normalizing the overall surface profile to denote statistically the area of relevance, termed the Zone of Interaction. From this baseline, depth of the trough and height of the plowed material are factored into the overall deformation assessment. Proof-of-concept data were collected and analyzed to demonstrate the performance of this proposed methodology. This technique takes advantage of advanced imaging capabilities that allow resolution of the scratched surface to be quantified in greater detail than was previously achievable. When reviewing existing data analysis techniques for conducting two-body abrasive scratch tests, it was found that the ASTM International Standard G 171 specified a generic metric based only on visually determined scratch width as a way to compare abraded materials. A limitation to this method was identified in that the scratch width is based on optical surface measurements, manually defined by approximating the boundaries, but does not consider the three-dimensional volume of material that was displaced. With large, potentially irregular deformations occurring on softer materials, it becomes unclear where to systematically determine the scratch width. Specifically, surface scratches on different samples may look the same from a top view, resulting in an identical scratch width measurement, but may vary in actual penetration depth and/or plowing deformation. Therefore, two different scratch profiles would be measured as having identical abrasion properties, although they differ significantly.

Chemical Mechanical Polishing Using Magnetic Composite Abrasives Slurry and Experimental Study on Polishing Performance

A polishing method that uses an auxiliary magnetic field is proposed,in which magnetic polymer microspheres/SiO2 composite abrasives are anchored on a smooth glass tool plate by the magnetic force,and the dependence between diameter of composite abrasive and morphology of tool plate is reduced.The auxiliary magnetic field is established by NdFeB permanent magnets with 8 mm diameter and different heights.The finite element method(FEM) analysis shows that the magnetic field with a concave-down columnar section has a uniform distribution of the force of magnetic field HdH/dz.Force analyses on magnetic polymer microspheres indicate that the magnetic force could help the magnetic polymer microspheres enter the polishing area from near-polishing area,and material is polished by magnetic composite abrasives in two-body abrasion wear mechanism.Experiments of polishing silica wafer,using a glass tool plate of Ra 0.5 μm surface roughness,have shown the superior characteristics with the assistance of the magnetic field.The material removal rate is increased from 66 nm/min to 179 nm/min,and the surface roughness of wafer is decreased from Ra 405.860 nm to Ra 0.490 nm.

Defining an abrasion index for lunar surface systems as a function of dust interaction modes and variable concentration zones

Unexpected issues were encountered during the Apollo era of lunar exploration due to detrimental abrasion of materials upon exposure to the fine-grained, irregular shaped dust on the surface of the Moon. For critical design features involving contact with the lunar surface and for astronaut safety concerns, operational concepts and dust tolerance must be considered in the early phases of mission planning. To systematically define material selection criteria, dust interaction can be characterized by two-body or three-body abrasion testing, and sub-categorically by physical interactions of compression, rolling, sliding, and bending representing specific applications within the system. Two-body abrasion occurs when a single particle or asperity slides across a given surface removing or displacing material. Three-body abrasion occurs when multiple particles interact with a solid surface, or in between two surfaces, allowing the abrasives to freely rotate and interact with the material(s), leading to removal or displacement of mass. Different modes of interaction are described in this paper along with corresponding types of tests that can be utilized to evaluate each configuration. In addition to differential modes of abrasion, variable concentrations of dust in different zones can also be considered for a given system design and operational protocol. These zones include (1) outside the habitat where extensive dust exposure occurs, (2) in a transitional zone such as an airlock or suitport, and (3) inside the habitat or spacesuit with a low particle count. These zones can be used to help define dust interaction frequencies, and corresponding risks to the systems and/or crew can be addressed by appropriate mitigation strategies. An abrasion index is introduced that includes the level of risk, R, the hardness of the mineralogy, H, the severity of the abrasion mode, S, and the frequency of particle interactions, F.

New Experimental Rig to Investigate Abrasive–Corrosive Characteristics of Metals in Aqueous Media

A new tribometer to investigate a conjoint effect of three-body abrasion and corrosion has been developed. In this design, a flat wear sample is loaded against a rotating cylindrical disc counterface and the abrasive slurry is delivered to the contact interface. Capabilities of the newly developed tribometer have been assessed through conducting abrasion–corrosion tests involving simultaneous electrochemical measurements. In this work, the stability of the passive layer on stainless steel under three-body abrasive wear in a near neutral electrolyte was investigated using potentiodynamic polarization tests. 316L Stainless Steel wear samples were abraded by coarse garnet particles in an aerated sodium sulphate electrolyte. The effects of load and speed on the polarization curves and passivity of 316L steel were determined. It was found that under abrasion–corrosion conditions 316L steel became more thermodynamically active and the passive corrosion rate has increased. Increasing the contact load resulted in a small increase in the passive corrosion current, while increasing the rotating speed had the opposite effect of decreasing the current. Linear polarization resistance method was used to analyse corrosion current changes with time during abrasion–corrosion testing. The existence of three distinct stages was explained by the third-body effect on the corrosion potential and current. First stage was revealed by continuous decrease of corrosion potential. Then, the potential reached a plateau for the second and third stages. In the first and second stages, particle constraint in the contact zone plays the major role and a linear rise in corrosion current with time has been recorded. After a certain amount of surface roughening, no further increase in particles entrapment is expected. Therefore, in the third stage steady-state corrosion current values are anticipated. The rig developed can also be used to simulate two-body abrasion–corrosion. The capabilities of the new rig have been compared against other experimental set-ups used in studies of combined abrasion–corrosion behaviour.

The Effects of Wear Debris under Fluid Flow Environment on Fretting Wear Mechanism of Nuclear Fuel Cladding Tube Supported by Supporting Grid

Nuclear cladding tubes are subjected to low-amplitude flow-induced vibrations (FIVs). Fretting wear occurs when two contacting surfaces are exposed to very low oscillation. Because nuclear cladding tubes are damaged by this fretting wear, it is necessary to try to evaluate the lifetime and improve the wear resistance of the tube. For this purpose, it is very important to clearly understand the damage mechanism of the tubes. Therefore, the present study undertook fretting-wear tests to investigate how the fluid that flows between the tube and the supporting grid affects the fretting wear. The governing damage mechanism consisted of abrasive wear and surface detachment behavior. In the case of the fluid flow environment, most of the wear debris was ejected from the contacting surfaces and this mode had a large effect on the maximum wear depth of the tube or wear amount. Additionally, the tests were performed under the water flow state as well as the water/air flow state. The result is that if the fluid flow exists, severe wear occurs through some mechanisms, such as two-body abrasion; further, the fluid flow decreases the contact load and attenuates the kinetics of oxidation. Because the severe wear due to two-body abrasion interrupted the formation of oxide film, wear amount was increased. Furthermore, even in the case of water/air flow environment, the worn surface was hardly oxidized due to extremely severe wear.

Two-body abrasive behavior of brake pad dry sliding against interpenetrating network ceramics/Al-alloy composites

Abstract Interpenetrating network composites containing 56 vol.% foam ceramics and 44 vol.% Al-alloy were fabricated in place of the conventional cast iron used for brake rotors. Experimental studies on phenolic resin brake pad dry sliding against the composites were performed on an Optimol SRV testing machine in order to examine the effect of temperature and load on friction and wear performances. Friction fade took place at high temperatures followed by overrecovery upon cooling. Wear showed an incremental tendency with temperature thanks to thermal decomposition of the resin. For applied loads from 32 N to 128 N, the friction and wear increased at 100 °C and 250 °C, whereas the former friction and wear were inferior to the latter, respectively. Topographic examination of the worn pad surfaces using scanning electron microscopy revealed that the pad two-body abrasion predominated over its three-body abrasion in determining the friction and wear.

Effect of abrasive particle size on abrasive wear of hardfacing alloys

Hardfacing is one of the most useful and economical ways to improve the performance of components submitted to severe wear conditions. This study has been made for the comparison of microstructure and abrasion resistance of hardfacing alloys reinforced with chromium carbides or complex carbides. The hardfacing alloys were deposited onto ČNS EN S235JR low carbon steel plates by the gas metal arc welding (GMAW) method. Different commercial hardfacing electrodes were applied to investigate the effect of abrasive particle size on abrasive wear resistance. The abrasion tests were made using the two-body abrasion test according to ČSN 01 5084 standard, abrasive cloths were of grits 80, 120, 240, and 400. Microstructure characterisation and surface analysis were made using optical and scanning electron microscopy. The results show the different influence of abrasive particles size on the wear rate for different structures of Fe-Cr-C system. The structures without primary carbides are of high abrasive wear rate, which increases nonlinearly with the increasing abrasive particle size. On the contrary, the structures containing primary carbides are of low abrasive rates and theses rates increase linearly with the increasing abrasive particle size.

Particle motion and modes of wear in the dry sand–rubber wheel abrasion test

In the dry sand–rubber wheel test, the particles are free to move between the wheel and testpiece. The particles may either roll as they pass through the contact, or they may temporarily embed in the rubber wheel and groove the sample; the motion of the particles will govern the modes of deformation of the sample and thus the dominant mechanisms of wear. In experiments concerning the abrasion of a range of steels with widely varying hardnesses, it has been shown that the motion of the particles through the contact depends not only upon the details of the testing conditions (for example particle feedrate, particle size and shape, applied load) but also upon the testpiece material properties themselves, such as hardness. Such a dependence upon testpiece material properties is a cause for concern for those who use the test, and indicates that observations of the mechanisms of wear are an essential part of this test methodology. Particle rolling through the contact is favoured by low applied loads and low testpiece hardness whereas particle sliding through the contact is favoured by high applied loads and high testpiece hardness. The wear coefficients in situations where particle sliding (grooving) occurs are not significantly higher than those for situations where particle rolling occurs and it is argued that this is associated with the way in which grooving particles orient themselves with respect to the testpiece as they pass through the contact. This is in contrast to fixed-particle grooving abrasion (such as might be observed in tests using abrasive papers), and as such, it is argued that what is commonly termed two-body abrasion should be subcategorised into “fixed-particle grooving abrasion” and “free-particle grooving abrasion”. The paper then proceeds to provide an analysis of the motion of particles in the dry sand-rubber wheel abrasion test, and seeks to understand the mechanics controlling their motion, and thus the dependence of particle motion upon external factors, focussing on the effects of testpiece hardness and applied load. The effect of hardness on particle rotation is well predicted by the model, but the effect of the applied load on particle motion observed experimentally is opposite to that which is predicted by the model. The shortcomings of the model are discussed, and the model has been qualitatively modified to account for this discrepancy. The modifications centre around the significant changes in rubber wheel–particle contact geometry as the applied load is changed; such changes are difficult to model analytically due to the large strains associated with such a contact, and it is suggested that finite element modelling may be required to fully understand and model the complex contacts occurring in this simple and widely employed test method.

Computer simulation of the two-body abrasion process modeling the particle as a paraboloid of revolution

Two-body abrasive wear is a process with strong stochastic characteristic. Abrasive particle geometry, distribution and worn surface morphology can only be statistically determined and analytical models therefore always cause large inaccuracy. In this research, the earlier model of a particle as pyramid with a hemispherical tip has been replaced by a paraboloid model of revolution. In the pyramid model the normal load cannot be large enough to penetrate beyond the height of the hemisphere. Generally, in practice the hemisphere tip is quite small, and it readily penetrates into the surface. A new particle model has, therefore, been devised to extend the normal load range. New contact equations are proposed for the particle geometry used in the present model. The Monte Carlo method and finite element methods (FEMs) have also been combined to calculate the wear rate of the material during simulation. It is found that the linear wear rate increases continuously during the running-in process and reaches a constant value after some travel distance. Computed roughness and worn surface morphologies are in agreement with the experimental data. Finally, a comparison between simulated and experimented wear rates has also made. Both data matched very well.