Dry Sand Rubber Wheel Abrasion Research Articles

Tribological behavior of HVAF-sprayed WC-based coatings with alternative binders

The tribological performance of High Velocity Air-Fuel (HVAF) sprayed WC-based cermet coatings with binders containing no or very limited amount of cobalt was evaluated under dry sliding, erosion, and abrasion wear conditions. The wear and corrosion behaviors of WC-NiMoCrFeCo, WC-FeNiCrMoCu and WC-FeCrAl HVAF sprayed coatings were investigated and compared to standard WC-CoCr coatings as benchmark. Microstructure characterization along with XRD analysis was conducted on all powders as well as the corresponding coatings. Comprehensive post wear analysis was conducted on all coatings subjected to ball-on-disk, gas jet erosion and dry sand-rubber wheel abrasion tests. Moreover, all coatings were exposed to 3.5% (wt./vol.) NaCl aqueous solution to evaluate their corrosion performance through electrochemical testing. XRD results showed negligible phase transformation between the powders and the deposited coatings. The WC-NiMoCrFeCo coating exhibited the best sliding wear and electrochemical corrosion performance, with an average specific wear rate value of 3.1 × 10−8 (mm3·N−1·m−1) and a corrosion current density of 1.9 μA/cm2. This coating also showed comparable abrasive wear resistance to the WC-CoCr coating. Under erosive wear conditions, too, the WC-FeNiCrMoCu and WC-FeCrAl coatings showed a comparable performance to the benchmark. Dominant wear mechanisms for the reference WC-CoCr coating, under sliding wear conditions, were abrasion (deep grooving) and surface fatigue (crack propagation and pitting). On the contrary, no pitting was observed in WC-NiMoCrFeCo and WC-FeCrAl coatings during the sliding wear test. No considerable difference was identified in the wear mechanisms of the different coatings under abrasion and erosion wear conditions. The results highlight the promise of some of the environment friendly binders studied to replace Co.

Evaluation of silicon effects on abrasion performance, microstructure and crystalline structure of NiHard-4 white cast iron using synchrotron X-ray diffraction

NiHard-4 is a class of abrasion-resistant white cast iron widely used in mining ore-handling operations. It has a multi-component microstructure consisting of eutectic carbides and metallic matrix, both of which can influence abrasion performance. This work investigates the influence of silicon concentration on abrasion performance, microstructure and crystalline structure. Abrasion was assessed by dry sand rubber wheel abrasion test (DS-RWAT), inner circumference abrasion test (ICAT) with quartzite, and ICAT with basalt. Abrasion performance trends were explained in terms of microstructure and crystallographic evolution, using SEM, macro-hardness, micro-hardness and nano-hardness measurements, cryogenic treatment and synchrotron X-ray diffraction (XRD). As Si content increases, duplex (M3C + M7C3) eutectic carbides are replaced with homogeneous M7C3 carbides, the latter confirmed to have significantly higher hardness. However, contrary to suggestions from literature that Si should enhance abrasion resistance, the tests found that elevated Si in NiHard-4 leads to inferior performance. In the metallic matrix, increased Si results in lower hardness, which synchrotron XRD indicates is due to reduction of dissolved carbon concentration in the austenite. It is demonstrated that the detrimental effects of Si on the matrix outweigh any beneficial effect that it may have on the eutectic carbides, leading to net inferior abrasion performance.

Comparing the abrasion performance of NiHard-4 and high-Cr-Mo white cast irons: The effects of chemical composition and microstructure

NiHard-4 and high-Cr-Mo white cast irons are two classes of abrasion-resistant cast irons extensively utilized in mining and related industries. Despite widespread usage, systematic performance comparisons between the two classes are lacking. Using four exemplar NiHard-4 and four exemplar high-Cr-Mo WCIs, this study compares the abrasive wear performance of the two alloy classes under a variety of conditions. The wear tests were the dry sand rubber wheel abrasion test (DS-RWAT), inner circumference abrasion test (ICAT) with quartzite, and ICAT with basalt. The resulting quantitative trends were interpreted and explained using bulk hardness, microhardness and nanohardness measurements, coupled with SEM of microstructures and worn surfaces.In all three abrasion tests the average wear life of high-Cr-Mo WCI was superior to NiHard-4. Average life improvements were 20% in DS-RWAT, 77% in ICAT-quartzite and 124% in ICAT-basalt. In the DS-RWAT there was overlap in the data and the difference between the two alloy classes was not statistically significant, but in the ICAT, for both rock types the two classes were strongly differentiated. Of various hypotheses considered to explain the results, the experimental evidence required that differences in carbide volume fraction or matrix hardness must be rejected. Instead it was shown that the superior performance of high-Cr-Mo WCIs was due primarily to their higher Cr:C ratio, resulting in higher Cr:Fe ratio and therefore elevated hardness and fracture toughness of the eutectic carbides.

Effect of Nanofillers on Abrasion Resistance of Carbon Fiber Reinforced Phenolic Friction Composites

The present study focuses on the development of polymeric friction composites with short carbon fiber, micron and nano-sized fillers, additives with varying weight% in phenol formaldehyde (PF) matrix using hot compression moulding process. The composites prepared with fillers viz. Molybdenum disulfide or Molykote (MK) and multi walled carbon nanotubes (MWCNTs) in carbon fiber reinforced PF matrix is designated as Set-I composites. Inclusion of graphite and nano-clay in carbon fiber reinforced PF matrix is designated as Set-II composites. The prepared composites are tested in Dry sand rubber wheel abrasion wear test rig, following ASTM standards for evaluating the abrasive wear behaviour. From the routine experiments, it was observed that the presence of combined micro and nanofillers i.e. 11.5 wt% MK + 0.5 wt% MWCNTs of Set-I, has shown superior abrasion resistance among the study group. The test results of the Set-I and Set-II composites are analyzed using Taguchi experimental design followed by analysis of variance (ANOVA) to understand the contributions of wear control factors affecting the abrasive wear characteristics. Further, worn surface of selected samples is analyzed using scanning electron micrographs.

Determination of Abrasive Wear Behaviour of Al-Fly ash Metal Matrix Composites Produced by Squeeze Casting

Squeeze casting is one of the processes in liquid metallurgy in which a molten metal is poured into a metallic die and is solidified under the action of a relatively high external pressure. The primary objective of this paper is to study the influence of the process parameters on wear resistance and hardness of squeeze cast LM6 Al-flyash composite. In this investigation Aluminium metal matrix composites, reinforced with flyash (from 5% to 12.5%wt.) was synthesized using stir-squeeze casting route. The influence of parameters like reinforcement content and squeeze pressure on the hardness and wear rate has been studied. The experimental results of the hardness and wear rate of the composites are compared with base alloy produced by squeeze casting. The results have shown that the wear resistance of the composites is very much superior to that of the base alloy produced by squeeze casting method. The abrasion tests were carried out by using a dry sand-rubber wheel abrasion wear testing machine. The test was carried-out at three different speeds (250, 300 & 350 rpm) and loads (2kg, 3kg & 4kg). The hardness test was conducted using Brinnel’s hardness tester. The macrostructural and microstructural studies of the MMCs were made using the TESCAN – VEGA3 scanning electron microscope in order to investigate the distribution of flyash particles in the matrix and on observation it was found that there is a reasonable uniform distribution of flyash in the matrix without any voids and discontinuities.

On replacing three-body abrasion testing with two-body abrasion testing

The dry sand rubber wheel abrasion test (ASTM G 65) is probably the most widely used abrasion test. It has been used for decades with favorable results. However, this test was developed when tool steels and fusion hardfacings were the materials usually ranked with this low-stress sand abrasion test. Two major problems have emerged in the use of this test: 1. The abradant (silica sand) is not aggressive enough for many modern materials. 2. There are many issues with the variability and availability of the rubbers used to force the abrasive against the test surface.This project was initiated to investigate the viability of using the ASTM G 174 loop abrasion test to replace or supplant the ASTM G 65 test. Friction tests were conducted on various substrates with rubbers wheels used in the three-body testing to understand the interface between the rubber and the abrasive. Limited tests were also conducted on replacing the rubber wheel in the three-body test with a steel wheel. Finally tests were conducted to develop a correlation between ASTM G 65 test results and ASTM G 174 test results. The friction tests confirm that various rubbers interact very differently with abrasives and substrates. A steel wheel cannot be used with the current ASTM G 65 force. The sand crushes to powder. However, a correlation curve was developed to allow conversion of historical ASTM G 65 data to results obtained with the ASTM G 174 two-body abrasion test. Overall this study suggests that two -body abrasion testing with aluminum oxide eliminates rubber issues and the aluminum oxide is abrasive enough to rank modern composites and cermets that are too wear-resistant for a sand abrasion test.

Prediction of the abrasion resistance of construction steels on the basis of the subsurface deformation layer in a multi-pass dual-indenter scratch test

Multi-pass dual-indenter (MPDI) scratch tests were carried out on a wide range of steels with different microstructures to investigate the relation between the formation of subsurface deformation layers under repetitive local sliding contact and their abrasion resistance. Five steel grades with different work hardening capability, i.e. Interstitial-Free steel, Fully Martensitic steel, Dual Phase steel, Quench Partitioning steel and TWining Induced Plasticity steel were selected. The results of this well-defined local contact damage test method and those of the standard ASTM G65 dry sand rubber wheel abrasion test were correlated. Results suggest that the abrasion resistance of steels is controlled by the properties of the work hardening layer formed beneath the abraded surface and depends on the thickness of the work hardening layer. When applying the correct evaluation parameters the new scratch test MPDI methodology reproduces the material response to the ASTM G65 abrasion test rather well and provides a reproducible and quantitative method to screen the abrasion resistance of new construction steels. Moreover, the MPDI test allows to quantitatively evaluate the abrasion resistance of steels for working conditions beyond those of the standardized G65 test.

Structure refinement effect on two and three-body abrasion resistance of high chromium cast irons

The effect of structure refinement on wear resistance of high chromium cast irons was investigated. The alloys were casted in molds containing a chill at the bottom in order to create a gradient of cooling rates, resulting in structures with carbide mean free paths ranging from 6.6±1 to 27.3±3μm. Two-body abrasive wear tests were carried out on a pin-on-garnet paper tester model PLINT TE79 as described in ASTM G132 standard, and three-body abrasive wear tests on the Dry Sand Rubber Wheel (DSRW) abrasion tester as described in ASTM G65 standard. Wear coefficient decreased sharply from 6.6 to 15μm of carbide mean free path and minor variations were obtained for coarser structures. All the samples showed cracking and fracture of M7C3 carbides. However, for the coarse structure it was verified that most of the larger M7C3 carbides showed only subcritical cracking and no fracture. The results suggest that the wear properties are not dependent on the bulk material hardness, but depend on structure refinement.

Microstructure and wear resistance of spray formed and conventionally cast high‐chromium white iron

A billet of hypoeutectic high‐chromium white iron (19% Cr, 2.5% C) was spray formed using Gas‐to‐Metal Ratios (GMR) of 0.9, 1.0, and 1.1. Microstructural studies and dry sand rubber wheel abrasion tests were carried out, on the one hand, to compare between the spray formed and conventionally cast material and, on the other hand, to investigate the relationship between gas‐to‐metal‐ratio, eutectic carbide morphology and abrasion resistance. The spray formed material was characterized by a considerably finer carbide morphology (max. ˜30 μm) than the conventionally cast material (max. 100–200 μm). The coarser carbide morphology is believed to be responsible for the superior abrasion resistance of the conventionally cast material. Although the carbide morphology of the spray formed material was only moderately influenced by the changes in the gas‐to‐metal‐ratio, there was a clear improvement in the abrasion resistance with decreasing gas‐to‐metal‐ratio. The improvement correlated with a decrease in the fraction of very fine (<1.5 μm) carbides, rather than with an increase in the mean carbide size.

Characterization and Comparison of Thermally Sprayed Hard Coatings as Alternative to Hard Chrome Plating

Thermal spray coatings have become one of the most potential for hard chrome replacement, particularly for wear and corrosion applications. In this study four types of hard coating materials were selected and thermally sprayed by suitable processes as the following designated codes (material/spray technique): Cr-Fe/HVOF, Cr-Ni/HVOF, WC-Ni/SF and Cr-Fe/AS. All of starting materials were characterized in order to create a correlation between spray materials and coating characteristics. SEM was employed for morphology and microstructure investigation. Particle size analysis was investigated by SEM and laser particle size analyzer. Coating characterization included surface roughness measurment by profilometer, porosity evaluation by image analysis and hardness test by Vicker microhardness tester. Microstructure of coatings was also revealed by SEM. Wear performance was evaluated by pin on disc test and dry sand rubber wheel abrasion test. Corrosion resistance was tested by potentiodynamic method. The results showed that particle size and morphology of starting powders were various depending on manufacturing method. Chemical compositions of starting materials showed great effect on coating properties and performance. Coatings deposited by HVOF and spray & fuse (SF) method showed typically dense and homogeneous structure than arc sprayed coating. WC-Ni/SF coating showed lowest abrasive wear rate compared to other thermally sprayed coatings. All Ni base coatings had significantly lower corrosion rates while Cr-Ni/HVOF coating had lowest corrosion rate. Although Cr-Ni/HVOF and WC-Ni/SF could be applicable for both wear and corrosion applications, for heat sensitive parts, Cr-Ni/HVOF coating could be a better alternative to spray and fuse.

Dynamic Mechanical Analysis and Three-Body Abrasive Wear Behaviour of Thermoplastic Copolyester Elastomer Composites

Various amounts of short fibers (glass and carbon) and particulate fillers like polytetrafluoroethylene (PTFE), silicon carbide (SiC), and alumina (Al2O3) were systematically introduced into the thermoplastic copolyester elastomer (TCE) matrix for reinforcement purpose. The mechanical properties such as storage modulus, loss modulus, and Tanδby dynamic mechanical analysis (DMA) and three-body abrasive wear performance on a dry sand rubber wheel abrasion tester have been investigated. For abrasive wear study, the experiments were planned according toL27orthogonal array by considering three factors and three levels. The complex moduli for TCE hybrid composites were pushed to a higher level relative to the TCE filled PTFE composite. At lower temperatures (in the glassy region), the storage modulus increases with increase in wt.% of reinforcement (fiber + fillers) and the value is maximum for the composite with 40 wt.% reinforcement. The loss modulus and damping peaks were also found to be higher by the incorporation of SiC and Al2O3microfillers. The routine abrasive wear test results indicated that TCE filled PTFE composite exhibited better abrasion resistance. Improvements in the abrasion resistance, however, have not been achieved by short-fiber and particlaute filler reinforcements. From the Taguchi’s experimental findings, optimal combination of control factors were obtained for minimum wear volume and also predictive correlations were proposed. Further, the worn surface morphology of the samples was discussed.

Further look at correlation between ASTM G65 rubber wheel abrasion and pin-on-disc wear tests for data conversion

It is desirable that wear testing results obtained using different techniques can be mutually converted. In this study, wear rates of two groups of materials, i.e. cast iron and steel, were evaluated using the ASTM G65 dry sand rubber wheel abrasion and pin-on-disc wear testers respectively. The conversion between results obtained using the two different methods was investigated. It was shown that the two sets of wear data can be mutually converted, following a linear relation. The slope and position of the line that fits the data are, however, affected by Young’s modulus of the materials and the applied load. Such effects are attributed to the fact that the wear rate of the materials measured using the G65 method was influenced by not only hardness but also elastic modulus, while for the pin-on-disc tests, the wear rate was more dominated by hardness of the target materials especially under larger applied loads. Relevant mechanisms are discussed with a further look at the Archard’s wear equation.

Investigations of abrasive wear of steel surfaces strengthened by vibro-arc carbonization/layering

Friction and wear losses can be reduced by arc welding, tempering and other methods. One of these technologies is vibro-arc surface processing. By using this technology surface can be carbonized through the formation of extra layers with supplementary materials. The present work is an investigation of an opportunity to increase abrasive wear resistance of steel surfaces by carbonizing them by vibro-arc (80 and 120 A current) layering with a graphite electrode and by dip-transfer surfacing welded through layers that create paste-like coatings that consist of materials increasing resistance to wear. The investigations have been performed according to the standards of ASTM G65-94—Dry Sand Rubber Wheel Abrasion Test, and ASTM G132—Standard Test Method for Pin Abrasion Testing. Studies have shown that through surface carbonization layers are produced with a higher wear resistance than surfaces formed with the wear resistant powder PG-10N-01. When using carbonization, the wear resistance of steel surfaces increases by forming austenite synthetic (Fe0.94C0.06), cementite (Fe3C), iron oxide (Fe3.71O4) structures. Even with the wear resistance increased up to 39–41%, the carbonization creates just thin layers of 0.1–0.15 mm. Surface welding with current pulses by using additional materials generates high temperature gradients. This deteriorates coating quality resulting in uneven thickness, formed cracks, voids. The formation of austenite synthetic (Fe0.94C0.06), cementite (Fe3C), chromium nickel (Cr2Ni3), chromium iron carbide (Cr21.34Fe1.66C6), carbon iron (C0.09Fe1.91) structures in a layer increases hardness (average 6145–6310MPa). Although the strengthened layer is much harder than steel Hardox 400, under abrasive wear conditions it has only 20–23% less wear resistance than Hardox 400. Due to surface defects, significant increases in hardness have almost no influence on the wear resistance. Surface quality is increased by welding at a lower current. Because just a thin layer is formed, the carbonization process is not an efficient technology to increase the abrasive wear resistance.

A Comparison of Mechanical and Tribological Behavior of Nanostructured and Conventional WC-12Co Detonation-Sprayed Coatings

In the present study, WC-12Co coatings were deposited by detonation-spraying technique using conventional and nanostructured WC-12Co feedstock at four different oxy/fuel ratios (OF ratio). The coatings exhibited the presence of phases like W2C and W due to the decarburization of the WC phase, and the proportions of these phases were higher in the nano WC-12Co coatings compared with conventional WC-12Co coatings. Coating hardness and fracture toughness were measured. The tribological performance of coatings was examined under dry sand rubber wheel abrasion wear, and solid particle erosion wear conditions. The mechanical and wear properties of coatings were influenced by degree of decarburization and more so in the case of nanostructured WC-Co coatings. The results indicate that the extent of decarburization has a substantial influence on the elastic modulus of the coating which in turn is related to the extent of intersplat cracking of the coating.

An Experimental Study on the Effect of Microstructure on Wear Behavior of Fe-Cr-C Hardfacing Alloys

Hardfacing is a low cost method of depositing wear resistant surfaces on metal components to extend service life. The prime requirement of a metal is to have good resistance to wear, corrosion and high temperature. A study has been carried out to investigate the relationship between abrasive wear resistance and microstructure of Fe-Cr-C hardfacing alloy. Two different commercial hardfacing electrodes were employed to investigate the effect of the microstructure. Results indicate that as hardness increases, the loss of wear decreases. Electrode-I has less wear as compared to electrode-II as the percentage of chromium, carbon and silicon is more in electrode-I. The abrasion tests were carried out in a dry sand-rubber wheel abrasion machine according to the procedure A of ASTM G65 standard. The factors such as, arc current, arc voltage, welding speed, electrode stick-out and preheat temperature, predominantly influence the weld quality.

Multiple Response Optimization of Three-Body Abrasive Wear Behaviour of Graphite Filled Carbon-Epoxy ComPosites Using Grey-Based Taguchi Approach

The three-body abrasive wear behaviour of carbon fabric reinforced epoxy (C-E) composites has been evaluated by the addition of graphite (G) particles as a secondary reinforcement. Three-body abrasive wear test were conducted using dry sand rubber wheel abrasion tester as per ASTM G-65 with three process parameters load, abrading distance and filler content. To assess the abrasive wear behaviour of particulate filled C-E composites satisfying multiple performance measure, grey-based Taguchi approach has been adopted. The experiments were designed according to Taguchi’s orthogonal array (L¬27). The grey relational analysis was applied to convert a multi response process optimization to a single response. Using analysis of variance, significant contributions of process parameters have been determined. The results indicate that the addition of graphite particles into C-E composite increased the wear resistance considerably. It was observed that highest wear resistance of C-E composite was achieved with incorporation of 10 wt. % of graphite filler. Results indicate that the filler content and grit size of abrasive paper were found to be the most significant factor which has influence on the abrasive wear of C-E composite. The worn surface features were examined through scanning electron microscope to probe the wear mechanism.

Three-Body Abrasive Wear Behavior of Basalt and Glass Fabric Reinforced Epoxy Composites

Three-body abrasive wear behavior of basalt–epoxy (B–E) and glass–epoxy (G–E) composites have been investigated using Dry sand rubber wheel abrasion resistance for various abrading distance, viz., 150, 300, 450 and 600m and different loads(22N and 32N) at 200 rpm. The weight loss and specific wear rate as a function of load and abrading distance were determined. The weight loss increases with increasing load and also with abrading distance while the specific wear rate decreases with increase in abrading distance and increases with the load. Better abrasion wear resistance was observed in B-E composite compared to G–E composite. Scanning Electron Microscope (SEM) is used to examine the abraded composite specimens and revealed that the more damage occur to glass fiber compared to basalt fiber. Also good interfacial adhesion was observed between epoxy and basalt fiber which leads to good abrasive wear resistance.

Abrasive wear behaviour of hard powders filled glass fabric–epoxy hybrid composites

The effect of incorporation of tungsten carbide (WC) and tantalum niobium carbide (Ta/NbC) powders on three-body abrasive wear behaviour in glass fabric–epoxy (G–E) composites was investigated and findings are analysed. A vacuum assisted resin transfer moulding (VARTM) technique was employed to obtain a series of G–E composites containing different fillers (WC and WC + Ta/NbC). Dry sand rubber wheel abrasion test was carried out at 200 rpm speed. The effect of different loads (22 and 32 N) and abrading distances (from 135 to 540 m) on the performance of the wear resistance were measured. The wear volume loss of the composites was found increasing with the increase in abrading distances and under the same conditions the specific wear rate decreases. The hard powders filled G–E composite systems exhibit lower wear volume loss and lower specific wear rate as compared to unfilled G–E composite system. The features of worn surfaces of the specimen were evaluated at higher and lower abrading distances at load of 32 N were using scanning electron microscope (SEM) and results indicate more severe damage to matrix and glass fiber in unfilled composite system as compared to hard powder filled composites.

Abrasive wear behavior of detonation sprayed WC–12Co coatings: Influence of decarburization and abrasive characteristics

The major objective of the present work is to evaluate the influence of decarburization of the WC–12Co coatings and also the abrasive characteristics on its abrasive wear behavior using a planned set of dry sand rubber wheel abrasion tests. Towards this purpose, detonation sprayed coatings have been deposited at three levels of oxygen to fuel ratios so as to obtain WC–12Co coatings with decarburization lying in the wide range of 4.4–45%. Additionally, to study the interrelationship between the abrasive characteristics and decarburization on abrasive wear, the abrasive wear tests have been conducted on WC–12Co coatings using three abrasives, i.e. SiO 2, Al 2O 3 and SiC. The results indicate that WC–12Co coatings with the decarburization levels of 4.4 and 34% results in similar abrasion rates irrespective of the type of abrasive used. However, WC–12Co coatings with a decarburization of 45% exhibited high abrasion rate and the observed increase in wear rate was also associated with a change in abrasion mechanism from one dominated by WC cuboid pullout to that of inter-splat cracking induced delamination. The wear induced subsurface damage has also been investigated.

Effect of microstructure on abrasive wear behavior of thermally sprayed WC–10Co–4Cr coatings

Thermally sprayed WC–Co coatings have been widely used in the coatings industry for its superior sliding, abrasive and erosive wear properties. In applications where corrosion resistance is also required in addition to wear resistance, WC–10Co–4Cr is the preferred coating composition. The coatings produced by different thermal spray processes exhibit a broad range of coating hardness, porosity and microstructural features like grain size and volume fraction of individual phases. In this study, we have evaluated the coating microstructures of various WC–10Co–4Cr coatings produced from different spraying processes, such as high velocity oxy-fuel (HVOF) and pulsed combustion. The objective of our study is to explore the abrasive wear mechanism of WC–10Co–4Cr coatings in great detail, and determine how these mechanisms are influenced by the coating microstructure. Dry sand rubber wheel abrasion test rig (based on ASTM G65) is used for evaluating the three-body abrasive wear properties of the coatings, using alumina as the abrasive material. The coating microstructural parameters including WC grain size, volume fraction, binder mean free path have been quantitatively measured, and correlation between abrasive wear behavior of coatings and its microstructural parameters is sought. This study shows that binder mean free path of carbides (which is a function of WC grain size and volume fraction) is a very important parameter affecting the abrasion resistance of good quality coatings (containing low porosity). The lower the binder mean free path, the higher is the abrasive wear resistance offered by the coating. This is because the abrasive wear mechanism of these coatings is dominated by preferential removal of the binder phase, followed by pullout of WC grains.