Abstract
Measurements were made on the indentation and friction of diamond hemispheres with various radii on Mn-Zn ferrite single crystals at a room temperature. Vickers and Knoop indenters were used in the indentation experiments. In the indentation and friction of ferrite, a plastic deformation occurs in ferrite, although the deformation is accompanied with the formation of cracks at higher contact loads. The relationship between diameter of indentation and load is expressed by the empirical formula, known as Meyer's law, where Meyer index takes a value of 2.2-2.0. A similar formula also holds in the case of sliding of hemisphere on ferrite, the index taking a value of 2.3-1.9. The critical load at which cracks are produced in the indentation or frictional track on ferrite is directly proportional to the radius of the diamond hemisphere. The critical loads on the sliding decrease to below half of those on the case of static indentation with same radius of hemisphere. The anisotropy of hardness of ferrite single crystal is fairly small. A little anisotropy of friction is also observed. Although the sliding on (100) plane exhibits a maximum anisotropy with sliding direction, the ratio of the friction in the [011] sliding to that in the [001] sliding is only a value of 1.2. The friction is slightly independent upon the crystallographic planes. It is concluded that the adhesion theory of friction is generally applicable to the frictional mechanism of ferrite single crystal. The relationship between frictional force F and contact load W can be expressed by the equation, F=αWc, where α and c are the constants. The value of index c approaches to unity with the increase of the radius of hemisphere.
