General Phenomenon of Transfer

Transfer of material from one surface to another is a common phenomenon when surfaces rub against one another, and Rabinowicz suggests that it may be universal in dry contact. Some material combinations are of course much less prone to transfer than others, but Bowden and Tabor describe transfer between a diverse variety of material pairs, inciuding lead selenide and rock-salt, chromium and diamond, tin and platinum, and tungsten, iead or copper and steei. 

For many pairs the adhesion is weakened because of poor lattice matching between the transferred material and the substrate, or major differences in their mechanical properties, or by poor cohesion within the transferred material. Conversely, it follows that smooth, effective transfer is more likely to take place when 

Reference has also been made earlier (Section 6.2) to the possibility of rupture of the counterface and of plastic flow of transferred material into a fissure so formed. This may result in strong attachment of the transferred substance, even if other factors tend to weaken that attachment. Continued transfer and back-transfer between the surfaces of two different materials may lead ultimately to a similar composition on both surfaces. As this condition is approached, there is an increasing tendency for the surfaces to adhere together. 

The factors which encourage material transfer are similar to those which lead to adhesive wear, since transfer is an essential first stage in the formation of an adhesive wear particle. The most severe form of adhesive wear is scuffing, and gross transfer commonly takes place under the influence of frictional heat when scuffing occurs. 

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