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It is shown, using electron microscopy, magnetic and friction methods, that a mixture of magnetic g-Fe 2 O 3 and abrasive powders, properly processed, can be used as a material for magnetoabrasive machining and polishing of variously shaped components.In recent years, a great deal of attention in mechanical engineering has been focused on finishing operations aimed at tightening the finishing tolerance of machined components; in this connection, there has been increased interest in the use of the magnetic abrasive machining (MAM) method. In the MAM method, a magnetic field is used to generate cutting and polishing forces to treat the surface of a machined part. The magnetic field behaves as an elastic bond for the abrasive ferromagnetic grains and allows more effective use of the abrasive's cutting edges; furthermore, it provides conditions for a small cutting force and a low surface temperature for finishing operations.The MAM method offers a number of advantages over the conventional techniques of abrasive treatment [1, 2]: (i) abrasive grains are spread uniformly over the treated surface, which allows effective finishing of complex-shaped components; (ii) the abrasive grains do not suffer from overloading; (iii) instantaneous temperature spikes can be readily avoided; (iv) the cutting temperature can be lowered to 473 K; (v) selective polishing is possible on ferromagnetic materials in which surface asperities (magnetic field concentrators) are cut off; (vi) the force (typically up to 1 MPa) at which the abrasive grains act on the surface treated promotes the formation of a new high-disperse phase and converts the tensile stresses into compressive.The readjustment of machine-tool equipment for handling components of different size and shape by the MAM method is not usually an easy task, and for this reason the use of MAM techniques is cost-effective either on large-scale production, or for solving special technological problems.The MAM machine tools can be classified with regard for the arrangement of magnetic poles: for cylinder-shaped components, for flat-surface components, and for small-size complex-shaped components; schematically, this is shown in Fig. 1 [3 , 4]. Magnetic abrasive (MA) materials with particles of different shape can be used; schematically, this is shown in Fig. 2.A general-purpose MA powder which would be equally good for roughing, cutting and polishing operations is yet to be developed. The conventional methods for preparation of adhesive powders are purpose-oriented and the powders pre-

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It is shown that fragmented particles are preferable to spherical particles for magnetic-abrasive finishing. The cutting elements of such powders are microscopic projections that determine the roughness of the finished surfaces. For a given volume of magnetic-abrasive powder, a decrease in the diameter of the particles increases the number of cutting centers. To maximize metal removal over the duration of the polishing operation and shorten the amount of time needed to reach the minimum value of Ra, it is necessary to use progressively finer abrasive powders as Ra decreases during polishing.Composite magnetic-abrasive materials (MAMs) ensure the maximum removal of material from the workpiece in magnetic-abrasive finishing (MAF) conducted with particles of different sizes. MAM performance depends on the conditions which exist during MAF, the dimensions of the working gaps, and the strength of the magnetic field. The shape of the grains of magnetic-abrasive powders has a significant effect on their cutting and polishing ability and a substantial effect on their service conditions.Inside the working gap of the MAF machine, Iron-based magnetic-abrasive particles -which exhibit shape anisotropy -are oriented in such a way that their major axis is parallel to the lines of force of the magnetic field and is perpendicular to the surface of the workpiece. The surface is finished by microscopic projections on the particles [1]. In addition to the magnetic forces, a magnetic-abrasive particle pressed against the surface being finished is acted upon by a frictional force that causes the motion of the particle to deviate in the direction of motion of that surface.Here, the cutting angle becomes negative and increases in absolute value, which adversely affects cutting conditions [2]. Studies of alsifer powders of spherical and fragmented form have shown (Table 1) that a fragmented shape offers more advantages than a sphere [3].Powders obtained by the same method were used for our investigation. Having a material of the same initial composition and performing simultaneous nitriding made it possible to obtain composite powders with granules having different geometries on the macroscopic scale but similar parameters (hardness, dispersity, dimensions) for the particles of the abrasive component -nitrides of silicon and aluminum, silicon carbide (green). The structural parameters of the granules were also similar, particularly the density of the distribution of the abrasive particles over the surface of the granules.Tests were performed on powders with a granularity of 200/160. The spherical and fragmented powders therefore