Sintering of composite materials for tool appointment, based on impact diamonds, under high pressure and temperatures

The article presents the results of a study of composite materials based on diamond-lonsdaleite abrasive (DLA) and various binders (Fe–Ti mechanocomposite, silicon carbide SiC). A metal-matrix composite material with a multimodal nano- and microlevel structure, characterized by increased adhesion of diamond grains to the binder, is obtained on the basis of impact diamonds and a Fe–Ti nano-mechanical composite. It is shown that the use of impact diamonds in comparison with synthetic diamonds makes it possible to reduce the pressure of thermobaric treatment by 30–50 % at the same sintering temperatures. The use of Fe–Ti–DLA composites in the process of magnetic-abrasive polishing (MAP) makes it possible to increase the removal rate of material based on silicon by 1.5–2 times and reduce the processing time by 30 % compared to ferroabrasive powder (FAP) based on synthetic diamonds. The effect of adding of silicon carbide on the process of obtaining a superhard composite material impact diamond – SiC is investigated. It is found that adding of SiC helps to reduce the defectiveness of the material and increase the homogeneity of its structure in comparison with the material without adding of a binder. In this case, an increase in the content of SiC and Si also leads to an inversion of the structure type of the superhard composite from polycrystalline to matrix. It is found that the additional use of amorphous soot and boron affects the refinement of the matrix structure of the composite material due to the formation of boron carbide and secondary finely dispersed silicon carbide.

DETERMINING OF MAGNETIC ABRASIVE POLISHING OF OPTICAL POLYMERS FOR SENSITIVE ELEMENTS OF RADIATION INDICATORS

Extending the durability of functioning of the sensitive elements of radiation indicators and increasing their reliability and safety are the main requirements for producers of modern radiation reconnaissance and monitoring devices. The proposed solutions for construction improving of products provide for the usage of optical fibers and the corresponding formation of loop-shaped channels in the finished sensitive polymer element. Potential possibilities of using magnetic abrasive polishing for finishing channel surfaces are considered. For the chosen construction of the polishing head, the material and form of the powder particles composition and the process parameters are proposed. The effect of the frequency and amplitude of vibration of abrasive particles on the depth of their penetration into the surface layer of the polymer is investigated. It has been determined that the widest possibilities of using powders of the composition Fe - C - Si - Ti with a diameter of d = 50 – 400 μm have a mode when the pressure of the air flow by feeding particles is maintained at a level of 1 atm, the magnetic induction of the field in the working gap is 0.8 T, the vibration amplitude of the particles is a = 0.4 mm, and the vibration frequency varies in the range f = 25 – 30 Hz.

Making Twist-Free Surfaces by Magnetic Assisted Ball Burnishing

As a well-known conventional finishing process, the grinding is commonly used to manufacture seal mating surfaces and bearing surfaces. It would lead to generate another finishing machining, which more cost-and energy-efficient, so the grinding process could be replaced by machining with roller burnishing or special type of polishing. The machined surfaces by turning or grinding usually have twist structure on the surfaces, which can convey lubricants such as conveyor screw. To avoid this phenomenon have to use special kind of techniques or machine, for example, rotation turning, tangential turning, ultrasonic protection or special toll geometries. All of these solutions have a high cost and difficult usability. In this paper, the authors describe a system and summarize the results of the experimental research carried out mainly in the field of Magnetic Abrasive Polishing (MAP) and Magnetic Roller Burnishing (MRB). These technologies are simple and also cheap while result the twist-free surfaces. During the tests, C45 normalized steel was used as workpiece material which was machined by simple and Wiper geometrical turning inserts in a CNC turning lathe. After the turning was used the MAP and MRB technologies to reduce the twist of surfaces. The evaluation was completed by advanced measuring and IT equipment.