During operation, nanostructured materials can be exposed to high temperatures, which have a significant effect on their properties. Studying the effect of temperature on various properties of nanomaterials, in particular, tribological properties, is an important task, the solution of which will make it possible to select the optimal architecture for specific operating conditions. In this work, we studied the effect of nanostructure parameters on the tribological properties of materials in the temperature range from room temperature to 1000 ° C. The regularities of changes in the tribological properties of nanolayer structures were revealed, which made it possible to determine the dependence of the adhesive (molecular) component of the friction coefficient fM on temperature. The effect of the fM value at elevated temperatures and thermal stability of this parameter on the functional properties of products with a modified surface layer has been established.
Fatigue microcracks, caused by mechanical or thermal impacts, are formed during periodic stretching and compression of the upper layers of nanostructured materials. Then, the microcracks grow further and merge, leading to the cleavage of the material fragment and its subsequent destruction. In this work, we have performed calculations and transfer showing that it is necessary to structure nanomaterials in such a way as to form residual compressive stresses, which can serve as a barrier to crack propagation, in them. Here we also show that shear stresses are largely responsible for initiating the microcrack formation in nanostructured materials.
Since the operating conditions of nanolayer systems are usually stochastic, modeling the processes occurring in them requires the use of probabilistic methods. The application of the method for calculating percolation by nodes and bonds for solving the problem of stochastic loading of nanolayer structures is facilitated in comparison with those usually used in various physical and technical problems. In this case the impact is not carried out at the boundary of the two-dimensional region of the nanomaterial, with the finding of stresses and strains inside the layer. Instead, stresses and strains are determined in the very surface layer of the material under the influence of an external load. Here we show that with an increase in the number of nodes and bonds in the system, the development of a crack is slow down and that the use of layered systems with a superlattice crystal structure, with minimized internal residual stresses, can provide increased crack resistance.
Nanostructured Ti-TiN coatings are one of the most common types of wear-resistant and corrosion-resistant coatings of machine parts and cutting tools. Multicomponent nanostructured coatings were deposited on AISI 318 substrates by vacuum-arc spraying by ion flux ratio for 30-45 seconds with formation of three types of Ti-TiN coatings: three-layer coating, multilayer coating and nanostructured coating. We propose to use the technology of Ti-TiN multilayer coating based on surface modification of the sample by bombarding with a high-current discharge using a “PINK” plasma generator, heating the substrate with ions of cathode material and obtaining cathode material condensation on targets followed by formation of multilayer coating. Target bombarding with an additional ion flux creates active nucleation centers where adsorption occurs and a fine-grained structure is formed. Ion bombardment significantly affects the physical and chemical properties of the sample surface. A detailed research of the change in the relationship of microhardness and adhesion strength of the coating depending on the type of coating of the sample was conducted, and corrosion resistance and wear resistance were investigated by high-precision signal processing from an automatic friction tribometer at a speed of 127 rpm for 60 minutes. As a result of data processing of measuring instruments during control of tribological and physical-mechanical characteristics it was established that formation of nanostructured coatings Ti-TiN with smaller thickness of Ti-TiN layer (30-100 nm) with submicrocrystalline structure allows to improve significantly physicalmechanical characteristics of samples.
The resistibility to corrosion of biocompatible metals is significantly reduced when plastic deformation of the surface layer is more than 0.5%. To increase the successful reliability of consolidation of bone tissues is proposed to use implants made of chemically pure titanium with a nanostructured biocompatible Ti-TiN coating to improve functional properties. An increase in functional properties is provided by improving coating deposition technology in an arc discharge plasma, which does not allow the formation of any impurities. The use of a high-current diffusion discharge in a vacuum chamber forms a controlled microstructure and the morphology of the implant surface, which increases adhesion during healing. The effectiveness of the proposed coating of implants is proved by the results of comparative tests on the study of the functional properties of samples without coating, with a coating applied by traditional technology and improved technology with a high-current diffusion discharge.
The article deals with the results of the study focused on the pattern of the distribution of heat flows in the cutting wedge of a carbide tool during the turning of steel. The influence of the wear-resistant TiN, (TiAlCr)N, and (AlTiCr)N coatings on the thermal state of the tool has been investigated. The results of the mathematical modeling have been compared with the data obtained by a method that relates the temperature in the cutting wedge of the tool to the changes in the microstructure and hardness of the material (the Wright and Trent methods). The experimental studies of tool life of the tools with the coatings under study and uncoated tools were carried out during the turning of AISI 5135 steel. It has been found that a tool with the (AlTiCr)N coating has the longest tool life which may be associated with a rational distribution of heat flows in the cutting zone and the cutting wedge of the tool. The use of self-organising wear-resistant coatings reduces the level of temperatures in the cutting zone by 8-20%.
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