The surface of the AlSi7Mg alloy was alloyed with CoNiCrW powder using a continuous wave fiber laser with a wavelength of 1.07 μm. The thickness of the alloyed layer is up to 4 mm. Its microstructure ...is radically different from the microstructure of the AlSi7Mg alloy. The basis of the microstructure of the alloyed layer is an α-solid solution based on aluminum, eutectic α + Si, and (Co,Ni)Al. The strengthening phases are aluminum oxides Al
2
O
3
, borides of the CrB type, and chromium carbides of various compositions. The alloyed layer is characterized by an average microhardness of 700 HV, an increased ability to resist elastoplastic deformation, and an increased wear resistance during abrasive wear tests. During wear tests under dry sliding friction conditions on a steel (0.2% C) counterbody, the alloyed layer is destroyed, which leads to an increase in mass loss during operation in such conditions.
Background. Continuous mechanical loads on the rails during its contact with the wheel lead to an accumulation of residual stresses in the surface layers of the rails, resulting in fast-growing ...fatigue cracks. In addition, the interaction of the wheel and the rail leads to micro-and macro-slip during their contact, abrasive wear, as well as plastic deformation of the rail. Rail grinding is the repair method by which defective material layers removes from the rail surface, provides the necessary accuracy of size and shape as well as surface quality. Objective. The aim of the work is to determine the effect of grinding on the tribological properties of the rail surface and establish the optimal parameters of the grinding process to ensure the best wear resistance of the rail surface. Methods. The research on wear and contact damage of samples of surfaces cut from grinding rails conducted on a friction machine M-22M. The studies were carried out by dry friction of a sample (cut from a rail) with a counter-sample from the material used in the manufacture of railway wheels, for 1 hour, the friction path was 3.60 km. Samples were weighed on a VLR-200 balance before and after the study was performed on the friction machine. As a result, the mass wear value was determined for each sample. Results. Based on the results of tribological studies, we obtained graphical dependencies of the wear intensity on the hardness of surfaces of samples and histograms which showing the effect of grinding process parameters on the amount of the wear intensity of samples. In the work was investigated influence the next main parameters of the grinding process on wear resistance there are the temperature of the rail, depth of cut, grinding wheel speed. The results of the work can find practical application in railway transport when repairing rails by grinding. Conclusions. Based on the analysis of experimental data, the empirical relationship revealed between the depth of cut, the surface hardness of the sample and the intensity of its wear. The nature of the influence of grinding process parameters (rail temperature, depth of cut, grinding wheel speed) on the wear resistance of the rail surface is established. The most optimal values of the process parameters that provide greater wear resistance of the rail surface are depth of cut - 0.007 mm, grinding wheel speed - 30 m/s, rail temperature - 20°C (it is better to conduct the processing of rails in the warm season). The results of the work can find practical application in railway transport when repairing rails by grinding.
We showed that the development of recommendations for a reasonable choice of linear block copolyurethanes that would be optimal for given operating conditions is still intuitive and does not consider ...the features of the molecular structure and the nature of initial components. We suggested a new scientifically grounded approach to the creation of linear block-copolyurethanes with increased wear resistance in relation to strength, deformation, thermophysical and tribotechnical characteristics. To simplify analysis of the properties of the studied materials, a mathematical model was developed, which describes the relationship between all considered properties of materials and their structure. We proposed to assess the relationship between structure and properties of the investigated materials by using quality indexes. Maximum values of quality indexes, depending on the operating conditions, correspond to different contents of hard blocks (Pc), and, consequently, to different molecular structure of the studied polyurethanes. Thus, it is reasonable to use block-copolyurethanes based on OBGA500 with a maximum content of hard blocks (Рс>60%) for operating conditions where it is necessary to provide high strength characteristics. Polyurethanes synthesized with the formation of clusters of hard blocks in the range of 45–55% are recommended for the use as wear-resistant materials.
Tw o complementary approaches should be used for the full characterisation of friction pair components. The first approach consists of stereometric studies of machined as well as worn surface ...topography of the friction components with multiple measurement methods used. The second approach, tribometric studies, enables the tribological characteristics of the friction pair. This work presents the complete characterisation of polymeric pin and ceramic plate friction pair components based on studies with the use of three research instruments: an interference microscope, a scanning electron microscope and a tribological tester. The results of the studies showed that the same treatment conditions used for different but similar ceramic materials did not provide exactly the same characteristics of both the machined and worn surface topography. Moreover, the results showed that the material properties and machined surface topography of the ceramic component significantly affected the friction coefficient and linear wear as well as the wear intensity of the polymeric component. Connecting the two approaches, stereometric studies and tribometric studies, allowed for a better identification of the wear mechanism of the polymeric pin (i.e., abrasion, fatigue and adhesion wear) and the kind of wear products (polymeric material).
Due to their excellent synergistic properties, Aluminum Matrix Composites (AMC) have achieved a high degree of prominence in different industries. In addition to strength, the wear resistance of ...materials is also an important criterion for numerous applications. The wear resistance depends on the surface topography as well as the working conditions of the interacting parts. Therefore, extensive experiments are being conducted to improve the suitability of engineering materials (including AMC) for different applications. This paper presents research on manufactured aluminum metal matrix composites reinforced with 10 wt.% of Al
SiO
(aluminum sillimanite). The manufactured and prepared samples were subjected to surface topography measurements and to tribological studies both with and without lubricant using a block-on-ring tester. Based on the results, analyses of the surface topography (i.e., surface roughness parameters, Abbott-Firestone curve, and surface defects) as well as of the tribological characteristics (i.a. friction coefficient, linear wear, and wear intensity) were performed. Differences in the surface topography of the manufactured elements were shown. The surface topography had a significant impact on tribological characteristics of the sliding joints in the tests where lubrication was and was not used. Better tribological characteristics were obtained for the surfaces characterized by greater roughness (determined on the basis of both the profile and surface texture parameters). In the case of tribological tests with lubrication, the friction coefficient as well as the wear intensity was significantly lower compared to tribological tests without lubrication. However, lower values of the friction coefficient and wear intensity were still recorded for the surfaces that were characterized by greater roughness. The obtained results showed that it is important to analyze the surface topography because surface characteristics influence tribological properties.
The linear dependence of abrasive wear under negligible shock actions as a function of the testing time has been established. The change of the wear intensity over time corresponds to the effect of ...the self-organization of wear.
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