We analyze the technology of hardening and restoration of products made of dispersion-hardened steels and steels containing large amounts of nonmetallic inclusions. For the formation of coatings, we ...used secondary raw materials obtained as a result of the utilization of a certain collection of ammunition, including nano- and dispersed diamonds. We also study the influence of parameters of the technology of detonation charge modification in the process of surfacing on the metal structure of the restored product. The best results were obtained as a result of introduction of 5.0–7.0% of charge (relative to the mass of the electrode). This guarantees the formation of a homogeneous structure with grains of similar sizes in the coating and increases the wear resistance of the restored product by 25% and of the mating product by up to 37%.
We study the causes and signs of degradation of cementite in chromium-nickel cast iron used for the production of massive forming rolls and the specific features of structural formation in cementite ...under the influence of operating temperatures and local strains formed in the rolls in the course of their operation. For this purpose, we use the procedure of high-temperature vacuum etching in order to detect dislocations, scanning electron microscopy, and the method of optical-mathematical description of the phases and their heterogeneity. It is shown that the degradation of cementite is connected with the formation of dislocation structures and diffusion, which promote the formation of new types of carbide phases with nonstoichiometric compositions, quasicrystalline graphite, and also ferrite and bainite. Possible combinations of newly formed phases are identified. They are also responsible for the stability of carbides. By analyzing the results of our studies of the degradation of cementite (regarded as a structural component specifying the level of hardness of the operating cast iron), we give recommendations concerning the possibility of improvement of stability of the cementite structure and decreasing the level of stresses in the rolls.
The multilayer ion-plasma coating TiN/CrN, 6 layers of CrN and 5 lauers of TiN, for hardening of piston rings is proposed. It is established that as a result of hardening, the wear rate of rings ...decreases 15.7 times. A new method for estimating the residual thickness of the coating, which gives recommendations for improving the quality of coatings, is proposed.
According to the results of simulation of stressed states, it is shown that coarse graphite inclusions formed in the walls of case-shaped parts of transient in thickness are the sites of initiation ...of defects due to the changes in the dislocation structure and diffusion of carbon from graphite. The cavities formed in graphite also promote the development of oxidation.
We study the process of wear of commercial oil-scraper piston rings of a D100 locomotive diesel generator in a reciprocating friction machine simulating their operating conditions. The degree of wear ...of these rings is determined by their weight and the increase in the working surface of a ring for different sliding speeds. We also evaluate the changes in their microhardness prior to and after tests. The character of structural changes of the friction surface for different parameters of testing is established by the method of electron-probe microanalysis. It is shown that the run-in tin coating is absent on the leading edges of the rings, where the characteristic friction bands are formed with the appearance of a graphite network of the substrate. A specific feature of structuring of the inclined surface is established in the area, where this surface is adjacent to the working collar. In order to increase the durability of these rings in operation, it is recommended to deposit ion-plasma nanocoatings with additional quality control and guarantee the relaxation of residual stresses.
Introduction. The completed developments are aimed at creating a new technology for increasing the wear resistance of a thin-walled instrument of complex configuration made of steel 65G for cutting ...beets at sugar enterprises. The most important requirement to improve the operability and durability of such a tool is the preservation of its profile and cutting edge during operation.
Materials and Methods. A new developed equipment and technological process of strengthening using low-temperature nitrogen plasma were used to solve this problem. There have been determined optimal processing parameters that ensure the formation of a quasi-morphic structure on the friction surface that reduces the defectiveness of the cutting edge after its machining and also provides a process of self-sharpening due to tool strengthening on one side.
Results. The comparative studies of the friction surface of products after operational tests have shown that their resistance increase significantly when strengthening both new and used products. This is determined by the nature of the quasi-morphic structure formed and the specific relief in friction on the working surface.
Discussion and Conclusion. To describe the new process of strengthening thin-walled products, the structure formation on the friction surface was analyzed in detail with the use of metallographic images and its phase relationship variability was estimated by the optic-mathematical analysis of various zones (compression and vacuum) formed as friction bands. This was done trough modeling with the estimation of the distribution density of the conditional colors of the analyzed fragments.
PDF
