Wear experiments were conducted with single and polycrystalline ferrites sliding on a cast iron disk on which an oil containing abrasives (1000, 4000 and 6000 mesh) was applied. The resulting wear surfaces were examined with electron diffraction, electron microscopy from replica and etching-rate method. Results of the investigation indicate that, for the single and polycrystalline ferrites, the deformed crystalline layers were exhibited by the Raether model in metals. The depth of deformed crystalline layer of ferrite, for the 1000 mesh abrasive of silicon carbide, is 2. 5 to 3 μm. It also, for the 4000 mesh or the 6000 mesh abrasives, is O. 8 to 0.9 μm. Surface cracking occurred as a result of sliding. The single crystal ferrites exhibited the same cracking depth as the deformed crystalline layer. The degree of cracking for the polycrystalline ferrites was more than that seen in single crystals. This is due to cracking along the grain boundaries of ferrite. In addition the wear mechanism of ferrite is discussed. Two wear mechanisms were observed. One was brittle fracture such as cleavage and quasi-cleavage on the 1000 mesh abrasives as a result of plowing and rolling of abrasives. The other was deformation in a plastic manner such as micro-cutting on the 4000 or 6000 mesh abrasives.

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Ferrite plates were rubbed against the cast iron disk on which the oil containing the abrasive grains (1000 or 4000 mesh) was supplied and wear of ferrite was studied. An olive oil was mainly used. A kerosene was also used in some experiments. Wear amount is directly proportional to the sliding distance. Wear rate α (mm/mm) generally varies linearly with the contact pressure P_n, although the α versus P_nrelation for the 4000 mesh grains in olive oil exhibits a breaking at a pressure of about 400 g/cm². When the 1000 mesh grains are used, the variation of wear rate with the crystallographic plane of ferrite is clearly observed and the degree of wear resistance is as follows: (100)>(110)>(111), (211). When the 4000 mesh grains are used, the wear rate is slightly dependent upon the crystallographic plane. In case that both abrasive grains are used, the wear rate of polycrystalline ferrite is greater than that of single crystal ferrite. This seems to be due to the occurrence of brittle fracture at the grain boundaries of polycrystalline ferrite. The values of the coefficient of wear are of the order of 10^-5 mm³/kg·mm for the 1000 mesh grains and of 10^-7 mm³/kg·mm for the 4000 mesh grains, respectively. An electron microscopy of ferrite worn surfaces suggests that wear on the 1000 mesh grains is mainly due to the brittle fracture such as cleavage and quasi-cleavage, while wear on the 4000 mesh grains seems to be mainly due to a plastic deformation such as micro-cutting.

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