A. K. Jha

Abrasive wear of Al alloy-Al2O3 particle composite : a study on the combined effect of load and size of abrasive

Abstract The two-body abrasive wear behaviour of a cast aluminium alloy (ADC12) and ADC-12–10 wt.% Al2O3 particle composite was studied at different loads (1 N to 7 N) and abrasive sizes (30 μm to 80 μm). The wear behaviour was predicted through statistical analysis of the measured wear rate at different operating conditions. The wear rate (Y) is expressed in terms of the coded values of the abrasive size (x1) and applied load (x2) by the following linear regression equation: Y alloy =21.32+2.21x 1 +13.72x 2 +1.83x 2 (1) Y composite =17.32+3.17x 1 +14.84x 2 +2.86x 1 x 2 (2) where the multiplication factor is 10−11 m3/m. Eqs. 1 and 2 above suggests the following: (i) the effect of load on the wear rate of both the alloy and composite is more severe as compared to that of abrasive size, (ii) the effect of load and abrasive size on the wear rate is relatively more in case of composite material than that of the alloy and (iii) at certain combinations of load and abrasive size, the wear rate of composite may be higher as compared to that of alloy. The above factors (i), (ii) and (iii) were explained on the basis of operating wear mechanisms.

Wear characteristics of a hardfaced steel in slurry

Abstract This study discusses some observations made during the wear testing of hardfaced layers deposited on a low carbon steel. Two kinds of (wear resistant) hardfacing materials were (separately) overlayed on a steel substrate and characterized for their microstructural features and wear behavior. Conditions of wear testing were varied in terms of the content of sand particles in the slurry, the speed of rotation of the specimens and the distance traversed. The substrate material was also subjected to identical tests in order to assess the effects of hardfacing/ overlaying. Hardfacing of the steel substrate resulted in a significant improvement in the wear resistance (inverse of wear rate) over that of the substrate, irrespective of the test conditions. Speed of rotation had a mixed influence on the wear rate wherein the intermediate speed caused maximum wear loss. The distance traversed had a mixed influence on the wear rate of the specimens in the sense that in some cases wear rate decreased with distance while a reverse trend was noted in the remaining situations, whereas under one test condition, the wear rate first decreased with distance, attained a minimum and then again tended to increase. Moreover, the larger sand content in the slurry led to lower wear rates. The wear behaviour of the specimens has been explained on the basis of the predominating material removal mechanisms, such as erosion and abrasion, in different situations. These have been further substantiated through their wear surface and sub-surface characteristics.

INFLUENCE OF MATERIAL CHARACTERISTICS ON THE ABRASIVE WEAR RESPONSE OF SOME HARDFACING ALLOYS

This study examines the abrasive wear behavior of two iron-base hardfacing materials with different combinations of carbon and chromium after deposition on a steel substrate. Effects of applied load and sliding distance on the wear behavior of the specimens were studied. Operating material removal mechanisms also were analyzed through the scanning electron microscopy (SEM) examination of typical wear surfaces, subsurface regions, and debris particles.The results suggest a significant improvement in the wear resistance of the hardfaced layers over that of the substrate. Further, the specimens overlaid with the material with low carbon and high chromium contents attained better wear resistance than the one consisting of more carbon but less chromium. The former specimens also attained superior hardness.Smoother abrasion grooves on the wear surfaces and finer debris formation during the abrasion of the hardfaced samples were consistent with wear resistance superior to that of the substrate.

Three-body abrasion of a cast zinc–aluminium alloy: influence of Al2O3 dispersoid and abrasive medium

Abstract Three-body abrasive wear characteristics of a cast zinc–aluminium alloy — 10xa0wt.% alumina particle composite have been analysed in the present investigation. Silicon carbide, sand and zircon particles were used as the abrasive media. In order to see the influence of alumina dispersoid particles on the abrasive wear behaviour, the similarly processed matrix alloy was also tested under identical conditions. The composite exhibited less wear rate than the matrix alloy irrespective of the test conditions. This was attributed to the wear resistance offered by the hard dispersoid phase, thereby protecting the softer matrix. Further, the SiC abrasive caused maximum wear rate while the specimens experienced the minimum when abraded against zircon particles; sand particles led to intermediate wear response. Wear rate of the samples decreased progressively with distance until a steady-state value was attained. Abrasion-induced work hardening was thought to be responsible for the decreasing wear rate with distance. Increased hardness of the (subsurface) regions as compared to that of the bulk also supported the view. Further, the rate of reduction in wear rate with distance was relatively more for the matrix alloy than the composite. This behaviour was more clearly visible and, at the same time, the extent of reduction in the wear rate with distance was maximum in the case of the SiC abrasive. Sand was observed to be more damaging than zircon despite its less hardness (than the latter). This could be owing to the sharp/angular shape of the sand abrasive in comparison to the round shaped zircon particles suggesting the predominant effect of the particle shape over the hardness of the abrasive. More severe loading conditions led to larger wear rates because of the greater depth of cut and more surface/subsurface damage. Observed wear response of the samples has been supplemented with the features of wear surfaces and subsurface regions. The latter also enabled an understanding of the operating wear mechanisms.

Wear response of a Zn-base alloy in the presence of SiC particle reinforcement: A comparative study with a copper-base alloy

An attempt has been made in this study to examine the effects produced by the reinforcement of (10 wt%) SiC particles on the sliding wear behavior of a Zn-base alloy. The matrix alloy was also subjected to identical test conditions to assess the influence of the SiC dispersoid phase. The wear characteristics of the (Zn-base alloy) composite and the matrix alloy were also compared with those of a Cu-base alloy (i.e., an aluminum bronze) in order to understand the scope of exploiting the Zn-base alloy matrix/composite as a substitute material for the latter (Cu-base) alloy.It has been observed that low frictional heat generated at the lower sliding speed (0.42 m/s) enabled the Zn-base (matrix) alloy to perform better than the composite material, while the Cu-base alloy showed intermediate wear resistance. On the contrary, the trend changed at a higher sliding speed (4.62 m/s) when high frictional heating caused the wear behavior of the Cu-base alloy to be superior to that of the Zn-base (matrix) alloy. The composite in this case performed better than the matrix alloy.The wear behavior of the specimens has been explained in terms of factors like microcracking tendency and thermal stability introduced by the SiC dispersoid phase and lubricating, load bearing, and low melting characteristics of microconstituents like α and η in the (Zn-base) alloy system and the thermal stability of the Cu-base alloy. It seems that the predominance of one set of parameters over the other actually controls the overall performance of a material. Once again, it is the test conditions that ultimately allow a particular set of factors to govern the other and influence the response of the specimens accordingly. The observed wear behavior of the samples has been substantiated further with their wear surface characteristics.

The Effects of Primary Silicon Particles on the Sliding Wear Behavior of Aluminum-silicon Alloys

Al±Si alloys are well known for their tribological applications involving the sliding motion of one component against another [1±4]. The process of material removal or failure under those circumstances becomes quite complex in view of a large number of factors relating to materials in contact and their conditions of movement. Material-related variables include the nature, shape, size, content and mode of distribution of various microconstituents of the sliding pairs [5±14]. On the other hand, experimental parameters that could be applied include load, sliding speed, environment, test con®guration, and so on [5±14]. Several studies have been conducted to assess the sliding wear behavior of Al±Si alloys [1±8]. However, attempts made to understand the role of microstructural features on the sliding wear behavior of the alloy system have been quite limited [5±7]. In view of the above, this study attempts to analyze how primary silicon particles in ̄uence the sliding wear characteristics of Al±Si alloys. The alloys were prepared by a liquid metallurgy route using a gravity-casting technique. The hardness of the metallographically polished samples was measured by a Vickers hardness tester. Tensile tests were performed on 6-mm-gauge-diameter, 32-mmgauge-length specimens at a strain rate of 1:04 3 10ÿ3 sÿ1. The apparatus used was an Instron universal testing machine (model 1185). Dry sliding wear tests were performed using a Ducom (Bangalore, India) pin-on-disc wear-testing machine (15) at sliding speeds of 1, 3 and 5 m sÿ1. The specimen size for conducting the wear tests was 6 mm in diameter and 40 mm in length. The counterface (disc) used was made of EN32 steel heat-treated to Rc 65 hardness. The sliding distance was ®xed at 500 m or until seizure of the specimens prior to traversing that distance. Pressure on the samples was applied in steps until the onset of specimen seizure was indicated in terms of abnormal noise in the pindisc assembly and large adhesion of the specimen material on the disc. A weight loss technique was adopted to determine the wear rate of the specimens. The temperature near the contacting surface of the samples was also monitored by inserting a chromelalumel thermocouple into a hole 1.5 mm from the contact surface. Table I shows the chemical composition and mechanical properties of the alloys. A larger concentration of silicon in LM29 alloy than in LM13 may be noted. Higher hardness but inferior tensile strength and elongation of the LM29 alloy as compared to LM13 is also evident. Fig. 1 represents the microstructural features of the alloys. Important microconstituents of the LM13 alloy were primary á and eutectic silicon particles (Fig. 1a, regions marked A and B, respectively). The LM29 alloy also revealed features similar to that of the LM13 alloy (Fig. 1a) except that primary silicon particles were also observed in the former case (Fig. 1b, region marked C). Fig. 2 represents the wear rate of the samples as a function of applied pressure at different sliding speeds. Wear rate increased with pressure. Also, increased speed at ®rst caused improved wear response of the alloys (Fig. 2). A further increase in sliding speed led the alloys to perform worse compared to the previous speeds. At the minimum sliding speed, the LM13 alloy performed better than LM29. However, the trend reversed at higher test speeds. The seizure pressure of the alloys has been plotted as a function of sliding speed in Fig. 3. The specimens attained reduced seizure pressure with speed. Further, the LM29 alloy showed its seizure pressure to be similar to that of the LM13 alloy at

Erosion–corrosion characteristics of squeeze cast aluminium alloy/SiC composites in water and sodium chloride solutions containing sand

AbstractThe erosion–corrosion behaviour of a squeeze cast aluminium alloy (Al–Cu) dispersed with either 10 vol.-%SiC particles or SiC fibres was investigated in slurry environments of 3%NaCl (aqueous) + 40 wt-% sand and water + 40 wt-% sand over a range of test durations at a linear speed of 7·06 m s-1. Test results indicated higher weight loss for the SiC composites than for the matrix alloy in 3%NaCl + 40 wt-% sand while the reverse trend was noted when the tests were conducted in water + 40 wt-% sand. Severe attack around the dispersoid/matrix and precipitate/matrix interfaces by the NaCl environment caused loosening of the dispersoid phase followed by the subsequent removal of the dispersoids. This resulted in a higher weight loss for composites than for the base alloy in NaCl containing sand. Corrosion processes appear to dominate in this case. The lower weight loss of the composites compared with the matrix alloy in water + 40% sand could be attributed to the protection provided by the SiC phase to ...

Influence of SiC reinforcement on the abrasive wear response of an Al-Cu alloy under conditions of varying abrasive size and applied load

Abstracts are not published in this journal

High stress abrasive wear behaviour of a hardfacing alloy: effects of some experimental factors

The high stress abrasive wear behaviour of an iron-based, low-chromium hardfacing alloy is dependent on the combined effect of the variables namely load, abrasive size, and sliding distance. A detailed analysis has been carried out to assess the effect of the various experimental factors on the high stress abrasive wear behaviour of a low-Cr hardfacing alloy. A study of this nature will help in choosing a hardfacing alloy depending upon its area/nature of application.

High stress abrasive wear behaviour of aluminium alloy-granite particle composite

Abstract The abrasive wear characteristics of aluminium alloy (LM6) and its cast composites dispersed with natural minerals, namely, granite particles, (10 wt.%) have been reported in this study. High stress abrasive wear tests using paper-mounted silicon carbide abrasive particles of various grit sizes were carried out at various applied loads. It was observed that the wear response of the specimens is influenced by the applied load, sliding distance and size of the abrasive particle. Results indicated that the addition of the dispersoid led to an improvement in the abrasion rate of the matrix alloy when abraded against fine abrasive particles over the entire range of applied loads and sliding distances. Similar trends were also observed with coarser abrasives at lower loads. However, at higher load and with coarser abrasive particles, the trend got reversed. Further, the wear rate reduced with sliding distance while the load affected the wear behaviour of the specimens in the opposite manner. These effects were more prominent under severe wear conditions of abrasion (i.e., higher load or coarser abrasive). The specimens characteristics have been explained on the basis of experimental observations.