The paper concerns the research on self-organization of the surface of coating of hypoeutectic alloy Fe-Mn-C-B modified Si, Ni, Cr, Cu with friction with C45 steel. The coatings were obtained by arc welding using a flux-cored wire. Tests of resistance to wear were carried out for hypoeutectic coatings with use of the friction pair pin-on-disc in the conditions of sliding friction, in model lubricating environments. The surface-active (glycerol oil) and inactive (Vaseline grease) lubricant was used. Tribological tests carried out showed that cooperation of hypoeutectic alloy coating with counterbody of C45 steel with lubrication with surface-active lubricant results in a significant improvement in tribological properties than in case of the lubrication with surface-inactive lubricant. The resulting effect is related to the self-organization of friction surface. After deposition and wear resistance tests, the friction surface microstructure was analysed, as well as the surface and depth distribution of the elements.
This paper presents the results of investigations that allow us to determine the influence of the temperature of plastic deformation in the range from 20°C to 800°C during static tensile tests on the mechanical properties and structure of low-alloy copper alloys of the type CuCo2 and CuCo2B, completed by measurements of the microhardness and observations of the structure in a light microscope, and also of fractures in a scanning electron microscope. Based on the results of these investigations the temperature range for the occurrence of the reduced plasticity of the alloys CuCo2 and CuCo2B could be determined. Keywords: low-alloy copper, plastic deformation, structure, mechanical properties, brittlenesŝ lanek predstavlja rezultate preiskav, ki omogo~ajo opredelitev vpliva temperature na plasti~no deformacijo v obmo~ju od 20°C do 800°C s stati~nimi nateznimi preizkusi na mehanske lastnosti in strukturo malo legiranih bakrovih zlitin, vrste CuCo2 in CuCo2B, izvedenih z merjenjem mikrotrdote ter opazovanjem mikrostrukture v svetlobnem mikroskopu in prelomov v vrsti~nem elektronskem mikroskopu. Na osnovi rezultatov teh preiskav je bilo mogo~e opredeliti temperaturno podro~je pojava zmanj{anja plasti~nosti zlitin vrste CuCo2 in CuCo2B. Klju~ne besede: malo legirani baker, plasti~na deformacija, struktura, mehanske lastnosti, krhkost
A wear resistance function was proposed to characterize relative wear resistance of materials. Submitted results make it possible to determine parameters of the wear resistance or durability of materials and protective coatings.Most frequently in tribotesting, a material's wear under sliding friction is characterized by the rate or intensity of the wear. These parameters enable us to make a comparative estimation of the relative wear resistance of materials for the case of equal external conditions of a triboprocess. Due to continuous change of pressure in a place of a tribocontact, e.g., in tribosystems with curvilinear boundaries, it is not possible to determine indicated parameters directly from an experiment. In such a case they can be described analytically by some function that relates wear intensity to the contact pressure.However, the wear failure of material is caused by a tangent load, i.e., the friction force and not by the normal pressure. The specific friction force x can strongly vary depending on the external conditions of the triboprocess for the same pressure in a tribocontact zone. Due to this fact, the friction durability of material should be connected with the specific friction force.As shown by wear research, damage accumulation is a fatigue process. In our previous testing [ 1 ], the function of the material durability qb was chosen as a characteristic of its friction durability. Starting from the definition that durability is the reciprocal of the wear, one can calculate it using experimental values of the linear wear h : O = L/h, where L is a track of the sliding friction.A dependence of 9 -x characteristic on the load on the tribocontact, which is evaluated by the friction force, was constructed to estimate the comparative durability of materials.There are different methods for the determination of the friction force on a contact in tribology. The simplest and rather correct one is the calculation using Coloumb's law: x = fp, where f is the sliding friction factor, and p is the pressure in the contact zone.To enhance clearness and simplify the comparison of the material's wear resistance and application of ~ = O('c) function, experimental results are approximated by the following relation in the analytical research of the durability of sliding tribosystems (~k(T,)-Bk[%iO)] mk( 1) where B, m, and x (~ are the characteristics of durability which are determined by the least square method, and k = 1, 2 is the numeration of the tribopair elements. Diagrams of material durability (DMD) (Fig. la, b) were plotted on the basis of these characteristics (see Table 1). After that the comparison of the materials durability under a certain loading is reduced to the comparison of functions of their durability, i.e., S21 -~21(x)~12(~),where $21 is the relative durability of material 2 with reference to material 1.
This paper presents the results of investigations on the effect of thermochemical treatment, boronising and chemical composition of selected structural steels on their wear in sliding friction process. The operation of boronising on C45, 37CrNiMo, 42CrMo6, 41Cr4, 50CrSi4-4 steels was performed by powder method at 950°C for 8 h. Following this operation, rod sections of the test steels were subjected to quench hardening from 850°C with isothermal holding at 300°C for 1h. The assessment of the construction, thickness and microhardness of boronised layers depending on the level of carbon and alloying elements in chemical composition of analysed steels was made. The testing for wear resistance of steels after boronising was carried out with the sliding friction method by applying a load of 150 N, counter-sample rotational speed of 1000 rpm and using aqueous solution of potassium chromate as a cooling medium. The metallographic observations of the structure and thickness measurement of the boronised layers were carried out using a light microscope, while the identification of phases was made by the X-ray qualitative analysis method. The hardness and microhardness measurements were taken by the Vickers method.
This experiment utilized five Aluminum alloys with silicon content percentages of 7, 10, 12.6, 14.5 and 17(wt)%. Ultrasonic vibration was applied to improve the quality of aluminum alloys. Sono-solidification, in which ultrasound vibrations are applied to molten metal during its solidification, is expected to cause improved mechanical properties due to grain refinement. Observed by microstructure photographs was that grains became smaller and their shapes more regular. Using ultra sound solidification α Al appeared during ultrasound treatment the eutectic solidification time was longest around 10% compared with same condition experiment without ultrasound treatment.
The paper presents the results of a SEM/EDS and XPS study of changing of chemical and phase composition of the friction surfaces Fe-Mn-C-B-Si-Ni-Cr hardfacing coatings depend on depth. The tribological examination was conducted in a pin-on disc system with unitary pressure of 10 MPa under dry friction conditions. A scanning electron microscope SEM/EDS as well as X-Ray photoelectron spectroscopy (XPS) were used to examine the structures on the friction surface and depend on depth 5, 10, 15, 20, 50, 100, 200, 6000 nm. The presence of compounds such as oxides (B2O3, SiO2, Cr2O3), carbides (Fe3C, Cr7C3), borides (FeB, Fe2B).
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