High-stress Abrasion Research Articles

Abrasive wear resistance of plasma-sprayed tungsten carbide–cobalt coatings

Plasma-sprayed coatings were produced by both air (APS) and low-pressure (VPS) methods from powders containing tungsten carbide with 9, 12 and 17 wt% Co. Abrasive wear tests under conditions of low stress (with a rubber wheel) and high stress (steel wheel) were performed with 100–150-μm abrasive silica sand on the coatings as well as on low-carbon steel control samples at loads between 29.4 and 117.6 N. The microstructures and phases present in the coatings were studied by SEM and X-ray diffractometry. In all cases, the wear resistance of the VPS coatings was greater than that of the APS coatings; all the coatings showed excellent resistance to low-stress abrasive wear, but showed a much poorer performance under high stress conditions. This behaviour was associated with extensive fracture of the carbide phase in high-stress abrasion .

Effect of high temperature and sub-ambient treatments on the matrix structure and abrasion resistance of a high-chromium white iron

The addition of NbC to high chromium white cast irons (WCIs) has potential to improve component wear lives in mining and ore beneficiation environments, due to the combined presence of Cr-rich and niobium carbides. While the effect of chromium carbide volume fraction (Cr-CVF) on abrasion performance of plain-Cr WCIs is well understood, its effect on NbC-bearing WCIs is unknown. This work studies the effect of Cr-CVF on high-stress abrasion of this newer class of dual-reinforced high-Cr WCIs, using the ball mill abrasion test with quartzite and basalt. The alloys cover a wide range of Cr-CVF, from M7C3-free NbC-reinforced steel to hyper-eutectic WCI. Bulk hardness increased linearly with Cr-CVF, at a rate of 3.9 HV per 1% Cr-CVF. In basalt, abrasion resistance increased linearly with Cr-CVF, at an average life improvement rate of 24% per 1% Cr-CVF. This confirms that performance is maximized by increasing Cr-CVF even in the presence of substantial volumes of cubic carbides. In quartzite the trend is again linear up to 30 vol% M7C3 (3.7% life increase per 1% Cr-CVF), but the hyper-eutectic alloy shows poorer resistance than slightly hypo-eutectic alloy. SEM studies of the worn surfaces demonstrate that micro-fracture of the hard carbides was the controlling damage mechanism. Primary M7C3 was observed to suffer fragmentation in high-stress abrasion in quartzite, confirming the expectation from the quantitative trend.

Two-body and three-body abrasion: A critical discussion

It is argued that the common classification of abrasive wear into ‘two-body abrasion’ and ‘three-body abrasion’ is seriously flawed. No definitions have been agreed upon for these terms, and indeed there are two quite different interpretations, the implications of which are mutually inconsistent. In the dominant interpretation, the primary thrust of the two-body/three-body concept is to describe whether the abrasive particles are constrained (two-body) or free to roll (three-body). In this view, two-body abrasion is generally much more severe than three-body. The alternative interpretation emphasises the presence (three-body) or absence (two-body) of a rigid counterface backing the abrasive. In this view, three-body abrasion is equated to high-stress (or grinding) abrasion and is generally more severe than two-body (low-stress) abrasion. This paper recommends that the ‘two-body/three-body’ terminology be abandoned, to be replaced by an alternative classification scheme based directly upon the manifest severity of wear.

Abrasion resistance of in situ Fe-TiC composites

Metal matrix composites containing a high volume fraction of carbide, nitride, boride, and/or oxide particles are frequently the materials of choice for applications which require high wear resistance. It is the very hard second phase particles which imbue the metal matrix composite with its superior wear resistance. For example, additions of titanium carbide (TiC), one of the hardest of the carbides with a Vickers hardness of 19.6--31.4 GPa, can be used to improve the abrasion resistance of iron alloys. In the present study in situ metal matrix composites, containing between 23 and 31 volume percent carbides, were produced from Fe-Ti-C and Fe-Cr-Ti-C melts, and their abrasion resistance was compared with that of unreinforced Fe and a white cast iron using a high-stress pin abrasion test.

The influence of heat treatment on the high-stress abrasion resistance and fracture toughness of alloy white cast irons

The influence of a range of austenitizing and subcritical (tempering) heat treatments on the high-stress abrasion resistance and fracture toughness of four commercially significant grades of alloy white cast iron was investigated. Complementing an earlier study[1] on the influence of a more limited range of heat treatments on the gouging abrasion performance of the same alloys, the results showed that the effect of austenitizing temperature on high-stress abrasion pin test weight loss differed for each alloy. With increasing austenitizing temperature, these results ranged from a substantial improvement in wear performance and retention of hardness through to vir-tually no change in wear performance and substantial falls in hardness. Fracture toughness, however, increased markedly in all alloys with increasing austenitizing temperature. Tempering treatments in the range 400 °C to 600 °C, following hardening at the austenitizing temperature used commonly in industrial practice for each alloy, produced significant changes in both hard-ness and wear performance, but negligible changes in fracture toughness. Most importantly, the data showed that selection of the correct temperature for subcritical heat treatment to reduce the retained austenite content for applications involving repeated impact loading is critical if abrasion resistance is not to suffer.

Abrasive wear study of selected white cast irons as liner materials for the mining industry

The abrasive wear behaviour of three white cast irons, designated as 10Cr-3.5Ni, 15Cr-3Mo and 16.5Cr-1.5Mo irons (where the compositions are in weight per cent), was studied in a field test as liners installed in a transfer of an iron ore operation and in three laboratory wear tests (pin-on-drum, dry-sand-rubber-wheel (DSRW) and paddle testers) to determine the relevance of the laboratory wear tests to the field liner test. The results from the wear tests and wear mechanism study showed that under the test conditions the DSRW test most closely predicts the relative wear rate of the white irons in the field liner test. However, a perfect match of both the wear mechanism and the rank of the wear rate for the iron from the laboratory wear test to the field liner test was not achieved, owing to the complexity of the field liner wear condition. The wear mechanisms were elucidated by microscopic examination of the worn surfaces for both field-tested liners and laboratory-tested specimens, and by subsurface examination of paddle-tested specimens, together with the microstructural study of the irons. The predominant wear mechanisms depend upon both the wear conditions and the microstructural properties of the irons. It was found that the wear resistance of the white irons for the low stress abrasion is controlled by the matrix, and that for the high stress abrasion and impact abrasion is mainly determined by the bulk hardness of the irons.

Laser remelting of plasma-sprayed coatings on cobalt-based alloys

Laser remelting of plasma-sprayed coatings can eliminate porosity and develop metallurgical bonding at the coating-substrate interface. In the present study, stellite no. 6 powder was plasma sprayed onto an AISI 1020 carbon steel. Suitable operating conditions for plasma spraying were initially determined. Under such conditions, the effects of laser remelting on the surface roughness, shear bonding strength and wear resistance were studied. The results show that surface roughness is reduced by the remelting process, and little porosity can be found in the remelted regions. The shear bonding strength is apparently increased by the remelting process. The improvement increases with the heat input of laser processing. Wear resistance against high stress abrasion is improved by the remelting process. However, for low stress abrasion, wear resistance is improved only by some remelting processes. The wear resistance increases with laser processing power for both wear tests.

High Stress Abrasion of Carbidic Hardfacing Alloys

The abrasion properties of a series of hardfacing deposits of chromium carbide alloys and tungsten carbide composites have been examined using the laboratory pin test. Corrt;lation between the abrasion resistance and variation in microstructural parameters of the deposited layers was determined for both 120 j1m garnet and 80 j1m alumina abrasives. The effects of alloy hardness (Hv) and volume fraction of primary carbide (Vc) on abrasion characteristics are shown to depend in a critical manner on abrasive type.

The effect of aluminum on the work hardening and wear resistance of hadfield manganese steel

A study has been made of the work-hardening and wear resistance of aluminum-modified Hadfield manganese steels ranging in composition from 1.00 to 1.75 Pct carbon and from 0.0 to 4.0 Pct aluminum. Aluminum additions reduced carbon activity and diffusivity in austenites of Hadfield’s composition, increasing the metastable solubility of carbon in Hadfield steel. Aluminum additions inhibited mechanical twinning and, by inference, increased the stacking fault energy of austenite. Increasing carbon in solution in austenite expanded the temperature range over which dynamic strain aging and rapid work hardening occurred. Simultaneous aluminum additions and increased carbon content increased the work-hardening rate and high-stress abrasion resistance of Hadfield steel, but there was an optimum aluminum content beyond which both declined. Maximum work-hardening rate was exhibited by an alloy containing nominally 1.75 Pct C, 13.5 Pct Mn, and 1.3 Pct Al. Improved high-stress abrasion resistance was also found in an alloy containing nominally 1.00 Pct C, 13.5 Pct Mn, and 4.0 Pct Al.

Mechanisms of material removal during low stress and high stress abrasion of aluminum alloy-zircon particle composites

(Al11.8Si4.0Mg alloy)-zircon particle composites containing zircon particle (size, 100 μm) volume fractions of 0.15 and 0.35 have been prepared by liquid metallurgy techniques. The low stress abrasion resistance of these composites was tested using a rubber wheel abrasion test apparatus with American Foundrymen's Society 50–70 mesh rounded quartz abrasive. Scratch tests were performed on metallographic surfaces of composites using a fixed-depth scratch test apparatus in order to simulate the high stress pin-on-drum abrasion test. The results show that the low stress abrasive wear rate of the aluminum alloy was decreased by a factor of 5 as a result of the dispersion of the 0.35 volume fraction of zircon particles. The wear rate of the composite containing a zircon particle volume fraction of zircon 0.35 (a Vickers hardness of 144 HV) under the low stress condition was found to be equal to that of normalized AISI 1045 steel (197 HV). Scanning electron microscopy micrographs of the composite surfaces abraded under low stress conditions show that the zircon particles stand proud of the matrix without any particle pull-out or interfacial debonding. Material removal mechanisms during low stress abrasion of the composites appear to be governed by microfracture of zircon particles, leading to subsequent pit formation. There is a direct correlation between material removal mechanisms during fixed-depth scratch testing and high stress pin-on-drum abrasion. In both cases there was catastrophic fragmentation of the zircon particles.

The use of transmission electron microscopy to study the effects of abrasive wear on the matrix structure of a high chromium cast iron

Abstract The wear behaviour of an austenitic high chromium cast iron was investigated under conditions of high stress abrasion using a specimen-on-track test apparatus. The austenite matrix at the wear surfaces of test specimens work hardened during abrasion giving hardness values up to 950 HV but the depth of hardening was seen to be much smaller than that obtained under service conditions. The nature of the work hardening was studied by thin foil transmission electron microscopy. This work has provided evidence of strain-induced martensite formation which is believed to be responsible for the observed increases in hardness.

Influence de la vitesse d'abrasion sur la mesure de la résistance à l'abrasion des matériaux

High stress abrasion resistance tests were carried out on some pure metals and steels with different microstructures. The speed of the abrasive belt was varied from 0.08 to 0.96 m s −1 to investigate its influence on the measured wear resistance. The speed of abrasion affects the results obtained for some materials. These variations could be due to a change in the critical attack angle caused by the action of the deformation rate and frictional heating on material ductility. Iron, which is very ductile, does not show any variation in wear resistance in the speed interval investigated. Titanium, less ductile than iron, shows a deterioration of wear resistance which can be due to a decrease in ductility caused by an increase in the deformation rate. Frictional heating seems to be important with molybdenum and tungsten. It increases the ductility of both metals, at different speeds however, and improves wear resistance. In general, the steels tested show a decrease in abrasion resistance at high speed, probably because of a decrease in ductility and, with a martensitic steel, of tempering by frictional heating.

Untersuchungen über die beeinflussung des gefüges karbidischer gusseisen bei abrasiver verschleissbean-spruchung

In this paper the mechanism of abrasive wear of white cast irons is examined on the microstructural scale. The Fe-C-Cr-Mo, Fe-C-Cr-Ni and Fe-C-V-Cr alloys were tested. The results of the test have shown that abrasive wear of white cast iron is the result of wear of the microstructural components. Under high-stress abrasion the carbide can be deformed, scratched, broken and uprooted. The matrix shows cutting and deformation work hardening and martensitic transformation. The abrasion behaviour of alloys with different microstructural matrices is markedly influenced by mechanisms of wear. During abrasion the austenitic matrix can undergo the form, the hardness, the kinetic energy and the pressure of abrasive particles.

Influence of abrasive hardness on the wear resistance of high chromium irons

The resistance to abrasive wear was determined for a series of alloyed white cast irons in a high stress abrasion test which utilizes a specimen in sliding contact with bonded abrasives. These were conducted on silicon carbide, alumina and two sizes of garnet abrasive. The results indicate that the hardness, or type, of abrasive used in the test significantly influenced the wear rate of white irons, i.e. the rate of wear increased with increasing hardness of the abrasive. Also, the results indicate that the type of abrasive used in the test was a significant factor in ranking white irons for resistance to high stress abrasion. When tested on silicon carbide or alumina abrasive, as-cast austenitic irons exhibited lower rates of wear than heat treated martensitic irons; when tested on garnet, an abrasive of lower hardness, those irons with martensitic matrix microstructures exhibited the same or less wear than irons with austenitic matrix microstructures. It was also evident that heat treated irons with martensitic matrix microstructures exhibited varying degrees of resistance to abrasive wear depending on cooling rates and alloy content.

Factors influencing the resistance of steel castings to high stress abrasion : T. E. Norman. Modern Castings, v. 33, May 1958, p. 89–98

Factors influencing the resistance of steel castings to high stress abrasion : T. E. Norman. Modern Castings, v. 33, May 1958, p. 89–98