Three-body abrasion

Metal polishing mechanisms appear to be considerably different from silica polishing. The critical event that determines the polishing process in metal CMP appears not only to be influenced by the crystallographic/microstructure deformation process but also to relate to more complex components of slurry [18]. To better understand the removal mechanism in metal CMP, tungsten is chosen, since both industrial and laboratory CMP data are available for this metal, and its abrasion behavior as a metal is similar to that of other ductile metals which have been studied quite extensively under two- and three-body abrasion [66]. 

In 1999, Luo and Domfeld [110] proposed that there are two typical contact modes in the CMP process, i.e., the hydro-dynamical contact mode and the solid-solid contact mode [110]. When the down pressure applied on the wafer surface is small and the relative velocity of the wafer is large, a thin fluid film with micro-scale thickness will be formed between the wafer and pad surface. The size of the abrasive particles is much smaller than the thickness of the slurry film, and therefore a lot of abrasive particles are inactive. Almost all material removals are due to three-body abrasion. When the down pressure applied on the wafer surface is large and the relative velocity of the wafer is small, the wafer and pad asperity contact each other and both two-body and three-body abrasion occurs, as is described as solid-solid contact mode in Fig. 44 [110]. In the two-body abrasion, the abrasive particles embedded in the pad asperities move to remove materials. Almost all effective material removals happen due to these abrasions. However, the abrasives not embedded in the pad are either inactive or act in three-body abrasion. Compared with the two-body abrasion happening in the wafer-pad contact area, the material removed by three-body abrasion is negligible. 

Abrasion occurs when one material is in contact with a harder material. Surface asperities of the harder material cut, plough, or indent characteristic scratches or grooves into the softer material (two-body abrasion). Abrasion can also be caused by hard particles that are trapped in between two surfaces (three-body abrasion). Irregular patterns of small indentations are formed. Contamination in the lubricants can significantly contribute to this type of abrasion. 

Abrasive wear occurs when asperities of a rough, hard surface or hard particles slide on a softer surface, and damage the interface by plastic deformation or fracture in the case of ductile and brittle materials, respectively. In many cases, the wear mechanism at the start is adhesive, which generates wear particles that get trapped at the interface, resulting in three-body abrasive wear. In most abrasive wear situations, scratching is observed with a series of grooves parallel to the direction of sliding.75... 

Attrition is the mechanical removal of hard tissue by direct contacts between teeth (either natural or restored) with no foreign substance intervening [5]. This mechanism causes wear by tooth-tooth contacts as well as by tooth-restoration, and indeed restoration-restoration contacts. The action of mastication and bruxism are known causes of attrition. In the field of tribology, the term abrasion refers to the loss of material from a surface by sliding, rubbing or scratching. Two-body abrasion refers to abrasion caused by two contacting surfaces in relative motion, i.e. the mechanism in dentistry that is described as attrition. Three-body abrasion refers to abrasion caused by surfaces in... 

In abrasive wear by hard particles we often find either two-body abrasive wear or three-body abrasive wear, as shown in Figure 5.3. Two-body wear is caused by hard protuberances on the counterface, while in three-body wear hard particles are free to roll and slide between two sliding surfaces. Wear rates due to three-body abrasion are generally lower than those due to two-body abrasion. Various mechanisms of material removal in these two cases differ only in relative importance. Slurry erosion belongs to the abrasive wear category. Erosion is caused by hard particles sticking to the surface entrained in a flowing liquid. 

Figure 5.3 Abrasive wear by hard particles often means either two-body abrasive wear or three-body abrasive wear (a) three body and (b) two body.

The wear situation is likely to be aggravated should hard additives of a coarser grain fraction be embedded in a softer matrix, such as clay, as the result of an upstream kneading process. This may lead to grain sliding wear (besides a two-body and even a proper three-body abrasive wear), which could, in the absence of an intermediate lubricating medium, have drastic consequences. Similarly, lack of an intermediate medium will favour any likely adhesive wear. 

Whilst the wear at the deeper cut flow channels has the profile of an erosion, three-body abrasive wear may occur, just as in the solids zone, if the flow cross-sections are reduced, as shown in illustration 6. 

Fig. 6 Schematic representation of the three-body abrasive wear...

The lapping process is a very complex three-body abrasion. During friction and wear processes, many AE signals could be generated because of the interactions, impact, dislocation, deformation, and removal of materials. In the area of tribology, AE was used to characterize wear mechanisms, discern plastic deformation and fracture, and to monitor active friction and wear processes. AE signals were related to friction coefficient, abrasive grit size, and wear rate. 

Buijs, M., and Korpel-van Houten, K., Three-body abrasion of Brittle materials as studied by lapping. Wear, Vol. 166,1993, pp. 237-245. 

Spanu, C., Marinescu, L, Pruteanu, M., and Hitchiner, M., Experimental comparison between two- and three-body-abrasion processes as applied to alumina ceramics. Transactions of NAMRI/SME XXXI, 2003,289-296. 

Abrasion is a form of cohesive wear that can occur in two modes, viz. two-body and three-body abrasive wear. Two-body abrasion refers to a hard rough surface, of which the asperities plough through the relatively stiffer counterface. The surface penetrations cause localised plastic displacement and indentations. Three-body abrasion refers to hard particles between two sliding surfaces, ploughing through at least one of the surfaces. The two are not mutually exclusive, as two-body abrasion can often lead to three-body when hard wear particles are detached from a surface. Abrasive wear is dependent on the bulk properties of the materials and the geometry of... 

Yousif, B. F. and El-Tayeb, N. S. M. (2008a). High-stress three-body abrasive wear of treated and untreated oil palm fiber-reinforced polyester eomposites. Proceedings of the Institution of Mechanical Engineers, PartJ Journal of Engineering Tribology 222(5), 637-646. 

MISRA A. and FINNIE I. An experimental study of three body abrasive wear" WEAR, 85 (1983) 57-69... 

The abrasion resistance of plastics can also be determined by the ASTM G 65 dry sand rubber wheel test (7), vriiich is shown schematically in Figure 2. The three-body abrasion produced by this type of test is simitar to that produced by rubbing plastic on a rigid surface with hard particles in the faying surface, but it is probably faster and easier to perform. Test times can be as short as one minute. This test can also be conduct immersed in a slurry (8) if this better simulates the system of interest. 

Somewhat similar is the abrasive tape test for plastics (9). This test rubs plaques of plastic against a contact roll covered with bonded abrasive tape. Mass loss in a prescribed amount of contact with the abrasive tape is the metric. The reference material for the test is wrought zinc. This test simulates severe abrasion. This testing standard contains a second procedure that rubs flat plastic specimens against flat plates covered wifti aluminum oxide particles. This is a three-body abrasion tribosystem as opposed to the two-body system used in the tape test These two tests and the Taber Abrasor test compete with each other and none is considered to be a reference abrasion test for plastics. 

Particle cleavage (erosion) Freely moving particles, which are carried in an intermediate medium between the base and counter body cause the wear (three-body abrasion). 

Abrasive wear is defined as the material loss when a hard particle is made to slide against a soft material. Abrasive wear is classified as two-body abrasion or three-body abrasion. In two-body abrasion, abrasive particles move freely over a material face as in sand sliding down a chute. In three-body abrasion, abrasive particles act as interfacial elements between the solid body and the counter body. It can be classified as high stress abrasion or low stress abrasion depending on the applied stresses. 

Two-body and three-body abrasion at elevated temperature... 

The work of Soemantri et al. [76] is presented in Fig. 6.15. Figure 6.15a shows the results of the two-body abrasion test, whereas Fig. 6.15b pertains to three-body abrasion. This work was carried out with commercially pure Al and Cu. As can be seen from Fig. 6.15, the wear rate of Cu is independent of temperature for two-body abrasion. Similarly, the two-body abrasive wear rate of Al is also nearly constant even though an increase in wear rate is noted at 323 K. In contrast, the wear rate of Cu increases with increase of temperature during three-body abrasion. However, for Al, the three-body... 

Effect of test temperature on abrasive wear rate (a) two-body abrasion (b) three-body abrasion [76]. 

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