SYNTHESIS OF ANTIFRICTION COATINGS BY THE FABO METHOD

In the paper, the technology of obtaining antifriction coatings by the method of finishing antifriction-free abrasive treatment with the implementation of the wear-free effect is proposed. (Research purpose) The research purpose is in developing an effective technology for obtaining copper coatings on the surface of steel parts of the shaft type to reduce the wear rate in the conditions of oil starvation of machine parts. (Materials and methods) During the study, a laboratory facility for the synthesis of antifriction coatings on the surface of steel parts by the method of finishing antifriction-free abrasive treatment has been developed. Brass of the LS-59-1 brand was used as a material for applying a copper antifriction coating. In order to activate the surface of the part and the surface of the filler material, a technological medium based on a ten percent solution of hydrochloric acid and glycerol was used. Authors determined the composition of the technological environment empirically. The obtained laboratory samples were subjected to tribological studies in comparison with standard antifriction alloys. X-ray diffraction studies were performed to determine the phase composition. (Results and discussion) As a result of X-ray diffraction studies of laboratory samples, the presence of iron and copper components in the synthesized coating was studied. The content of oxides on the surface of the coating is insignificant, the internal structure is dense with no visible porosity. The coating consists of 95 percent copper, the synthesis process takes place without oxidation, which gives the coating a high adhesive and cohesive strength. The coating thickness is uniform and varies within 3-5 micrometers. (Conclusions) Comparative tribological studies have shown high resistance to wear and to the setting of the contact surfaces under conditions of oil starvation. The coefficient of friction is stable and low and is in the range of 0.08-0.15. The developed technology makes it possible to increase the wear resistance of steel parts of the shaft type in the shortest possible time and with minimal material costs and can be successfully implemented in the conditions of repair enterprises.

Mathematical model of honing of gas-dynamic supports

The design of technological processes for the manufacture of gas-dynamic supports (GDO) of gyroscopes is traditionally based on the use of finishing operations with the use of free abrasive. This leads to a high complexity of manufacturing such devices and complicates mass production. Reducing the labor intensity is possible when the labor-intensive finishing operation with a more productive operation of honing the holes of the GDO is replacing. But such a replacement requires the development of high-precision technology, which implies mathematical modeling of the process of honing the holes of GDO gyroscopes made of ceramic CM-332. Objective – a mathematical model of the process of honing the holes of GDO gyroscopes made of ceramic CM-332 is developed, which allows for the known shape of the workpiece, the tool used and the technological modes to calculate the geometric shape of the processed hole, and the value of any error. A mathematical model of honing of precision holes of GDO gyroscopes is developed, which takes into account the main factors of the process, the characteristics of the tool and the technological modes of processing. The dependence of the accuracy of the geometric shape of the processed hole on the characteristics of the tool is determined. The use of the results of the study made it possible to reduce the labor intensity of finishing operations for processing GDO holes by 10-15 times in the conditions of mass production of gyroscopes.

SYNTHESIS OF ANTIFRICTION COATINGS BY THE FABO METHOD

In the paper, the technology of obtaining antifriction coatings by the method of finishing antifriction-free abrasive treatment with the implementation of the wear-free effect is proposed. (Research purpose) The research purpose is in developing an effective technology for obtaining copper coatings on the surface of steel parts of the shaft type to reduce the wear rate in the conditions of oil starvation of machine parts. (Materials and methods) During the study, a laboratory facility for the synthesis of antifriction coatings on the surface of steel parts by the method of finishing antifriction-free abrasive treatment has been developed. Brass of the LS-59-1 brand was used as a material for applying a copper antifriction coating. In order to activate the surface of the part and the surface of the filler material, a technological medium based on a ten percent solution of hydrochloric acid and glycerol was used. Authors determined the composition of the technological environment empirically. The obtained laboratory samples were subjected to tribological studies in comparison with standard antifriction alloys. X-ray diffraction studies were performed to determine the phase composition. (Results and discussion) As a result of X-ray diffraction studies of laboratory samples, the presence of iron and copper components in the synthesized coating was studied. The content of oxides on the surface of the coating is insignificant, the internal structure is dense with no visible porosity. The coating consists of 95 percent copper, the synthesis process takes place without oxidation, which gives the coating a high adhesive and cohesive strength. The coating thickness is uniform and varies within 3-5 micrometers. (Conclusions) Comparative tribological studies have shown high resistance to wear and to the setting of the contact surfaces under conditions of oil starvation. The coefficient of friction is stable and low and is in the range of 0.08-0.15. The developed technology makes it possible to increase the wear resistance of steel parts of the shaft type in the shortest possible time and with minimal material costs and can be successfully implemented in the conditions of repair enterprises.

Experimental Study of the Impact of a Vibrating Wire on Free Abrasive Machining as Correlated to the Modeling of Vibration Subject to an Oscillating Boundary Condition

In this paper, we study experimentally the impact of a vibrating wire on the free abrasive machining (FAM) process in removing material from the surface of brittle materials, such as silicon. An experimental setup was designed to study the FAM process on silicon substrate surface by using a slurry-fed wire with a periodic excitation. An analytical solution of a wire moving axially, subject to an oscillating boundary condition with damping from abrasive slurry, was derived based on the partial differential equation of motion. Experiments were conducted on the apparatus using a wire with an oscillating boundary. It was found that the amplitudes of vibration were larger at the side of the oscillatory boundary, which caused more FAM interaction near the edge of the oscillatory boundary with larger material removal that was measured and validated. Furthermore, experiments were conducted to elucidate the effectiveness of brittle material removal using FAM with abrasive grits: (i) under dry condition, (ii) with water, and (iii) with abrasive slurry. Experimental results showed that the vibration of wire resulted in plastic deformation on the surface of silicon wafer. The abrasive grits in slurry driven by a vibrating wire generated material removal through observable grooves and fractures on the surface of silicon due to FAM in just a few minutes. The grooves from FAM process is an outcome of brittle machining through fracture formation and concatenation, generated by the indentation of abrasive grits on the silicon surface.

Research on Subsurface Damage of Lapping Sapphire with Diamond Fixed Abrasive

The depth of surface/subsurface damage layer is the key index of surface quality of sapphire. In this paper, that depth model of the surface/subsurface damage lay characterized by the crack length was established according to the mechanical theory of indentation fracture. The cutting relation between abrasive and workpiece and the difference of the depth of subsurface damage crack are analyzed. It is preliminarily estimated that the length of sub-surface damage crack of free abrasive sapphire is about 2.46 times that of fixed abrasive when considering only the contact hardness of abrasive grain under static load. Diamond abrasives with size of W20 were adopted to carry out experiments in free and fixed lapping methods. The results show that the surface/subsurface damage depth is 9.87μm and 3.63μm respectively. It is easier to obtain good sub-surface quality by using the fixed abrasive method than free abrasive at the same particle size.