Malkin defines attritious wear referring to the development and growth of wear flats on the tips of active grains. Attritious wear is measured by the percentage of the wheel surface covered with wear flats [MALK68, p. 36]. Jackson defines attritious wear as wear that occurs “atom by atom” by physical and chemical interaction between grain and workpiece [JACK11, p. 8]. Several wear mechanisms are responsible. Surface shattering, fatigue, and softening result from the basic wear mechanisms explained in the following.
6.4.2.1 Abrasion
Abrasion occurs when roughness peaks of a counter-body or particles in a medium penetrate the body’s surface and perform a movement parallel to the surface simultaneously. This leads to formation of grooves and micro chips [HABI80, RABI95]. The extreme grinding pressures and temperatures initiate oxidation and diffusion processes in the grit surface layers, which decrease the abrasion resistance of the grit material [KLOC05a].
Abrasion occurs differently at ductile and brittle materials. Brittle materials wear by particle breakouts [HABI80]. Anisotropic materials such as diamond have different resistances against abrasion in their different crystallographic planes. Abrasion at diamonds is a micro fracture process. Micro cracks spread in the loaded zone and atom bonds break due to stress accumulation [SEN91, WILK91]. Micro fracture processes occur mostly along octaheder planes because there are less atom bonds to break than along the other planes [WILK62]. The border between abrasion and breakage as failure mechanisms is hard to define.
Minke [MINK88] found groove marks on dressing diamonds which gave the impression that the diamonds were scratched by softer corundum grits. This effect is explained by temperature related hardness decrease of the counter parts. The thermal stability limit of diamond (about 700 °C) is attained earlier than the one of corundum (about 1160 °C).
Ludewig [LUDE94, p. 61 ff] derives that plastic deformation of corundum grits is possible. The grinding temperatures of 1400 °C lead to a decrease in toughness (about 40 % of toughness left compared to 25 °C). In this region, the bearable compressive stresses of corundum are met during the grinding of hardened steels.