Tribological tests of a hybrid composite (Al–12Si)–40Sn prepared by sintering mixtures of powders of silumin and pure tin were carried out using the pin-on-disk scheme. It has been established that ...an increase in the sliding velocity decreases the wear intensity of the composite upon dry friction, while an increase of the load leads to the opposite result. The data obtained indicate that the main contribution to the wear of the composite comes from the delamination of strongly deformed subsurface layers of the material. With an increase in the sliding velocity, the mechanism of the wear does not change, but, because of the heat-induced softening of the material, wear particles of the steel counterbody are pressed into it that “plate” the surface of the sample and reduce its wear intensity.
The structure and tribological properties (coefficient of friction, wear) of the composite material based on a commercial AO20-1 aluminum alloy reinforced with Ti
2
NbAl intermetallic particles have ...been analyzed. Structures of various degrees of dispersity are formed upon melt crystallization in a copper or graphite mold. The composite material formed in the copper mold is found to be characterized by a more disperse granular structure and a better intermetallic particle distribution. The wear intensity and the coefficient of friction of the composite material decrease by ≈2.5 times in comparison with the AO20-1 matrix alloy. When the test load increases, the coefficient of friction of the modified alloy decreases insignificantly.
Abstract (1) Dental wear is a common phenomenon in mammals. Its occurrence is influenced by tooth anatomy, animal physiology, biomechanics and behaviour. So far, investigations of dental wear in ...cetaceans have been scanty and superficial. We compare the frequencies of occurrence, location and intensity of dental wear in some species of dolphins from southern Brazil, South Atlantic Ocean. (2) Teeth of ten species were evaluated using a stereoscopic microscope to identify wear facets, which were classified according to location, anatomical position and wear intensity. (3) Frequencies of dental wear were high for all species with exception of Delphinus capensis , with less than 50% of teeth worn. Simultaneous wear facets in the apex and lateral of teeth were more common than facets restricted to the apex or lateral faces. Wear on the dental crown was more common, but some species showed less frequent wear down to the cingulum or root level. Superficial wear seems to be the general trend for dolphins, but Stenella coeruleoalba and Pseudorca crassidens showed a higher frequency of severe wear. Only for Tursiops truncatus the frequencies of wear were significantly different between males and females. When considering the ontogeny of dental wear, only for T. truncatus and Stenella frontalis indexes of dental wear were correlated with body length. (4) Whether dental wear has implications or not in fitness and feeding behaviour, severely worn teeth may expose the pulp cavity and increase the susceptibility to local infections.
One of the most important issues to be addressed in hard cutting pertains to the evaluation of tool life as it is closely connected to machining quality and overall process cost. The attributes of ...tool life can be mathematically calculated based on machining conditions and other characteristics of the cutting process. In this paper the formulation developed for CBN tools, applied for the machining of 100Cr6 bearing steel is presented. Experiments were carried out for the validation of the theoretical approach. Additionally, a novel indicator, namely wear intensity, is analyzed and discussed, based on experimental results. Wear intensity is calculated as the ratio of flank wear to cutting length. From the analysis it can be concluded that the prognosis of tool life can be accurate with the proposed method. Furthermore, interesting and useful results are reported in connection to wear intensity and cutting speed in hard cutting.
The effect of equal channel angular extrusion (ECAE) with route A on the wear resistance of sintered Al–Sn alloys has been studied in this work. The tribological tests were carried out according to ...the “pin-on-disk” scheme without liquid lubrication. It was established that multiple processing by this method leads to the strengthening of the aluminum matrix and the formation of a structure with alternating Al and Sn layers which is favorable for the self-lubrication process. The wear resistance of the sintered Al–Sn alloys is increased as a result. However, the number of ECAE passes should be limited to two to three because a fragmentation of thin tin interlayers and destruction of the layered structure take place after large number of the passes.
Wear Resistance of High-Entropy Alloys Firstov, S. A.; Gorban’, V. F.; Krapivka, N. A. ...
Powder metallurgy and metal ceramics,
07/2017, Letnik:
56, Številka:
3-4
Journal Article
Recenzirano
The tribotechnical properties of high-entropy alloys in pair with 65G steel in air under dry sliding friction conditions are investigated in comparison with wear-resistant steel and powder materials. ...The sliding friction rate was 6, 8, and 12 m/sec and the pressure was 0.5 and 1.0 MPa. It is determined that the wear intensity of high-entropy alloys at the sliding friction rate 5–10 m/sec under 0.5 and 1.0 MPa loads ranges from 6.1 · 10
–10
g/km to 1.6 · 10
–9
g/km for the samples and from 5.5 · 10
–8
g/km to 1.1 · 10
–8
g/km for the counterface. It is established that, when friction, the shear deformations promote the formation of thermally stable nanostructures with grains 30–70 nm in size in the surface layer of the secondary structures. It is shown that the formation of nanostructures is accompanied with 20–30% increase in hardness for both high-entropy alloys and counterface material. It is established that, when friction, high temperatures at the contact points promote the formation of ordered β-phase with BCC lattice on the friction surface of the Fe
25
Cr
20
Ni
20
Mn
15
Co
10
Al
10
high-entropy alloy.
Plasma electrolytic nitriding of steels Belkin, P. N.; Kusmanov, S. A.
Surface investigation, x-ray, synchrotron and neutron techniques,
07/2017, Letnik:
11, Številka:
4
Journal Article
Recenzirano
This review deals with the current scientific and technical results of the plasma electrolytic nitriding of constructional steels. The physicochemical features of diffusion saturation from vapor‒gas ...media are revealed and developed electrolyte compositions and nitriding modes are presented. The structural peculiarities of the nitrided layers and their interrelations with microhardness, strength characteristics, and wear and corrosion resistances are described. The advantages of plasma electrolytic treatment and promising areas for development are noted.
The article proposes a hypothesis on the nature of anti-adhesion processing method by the magnetic field of cutting and deformation tools based on the analysis of operating experience and ...experimental studies of a wide range of tools. The results of the wear process experimental and mathematical modeling in terms of increasing the magnetic impact are presented. It is found that with the increasing number of impulses, the external magnetic field decreases wear and increases the residual magnetic induction of the samples processed by the magnetic field, and the quantification of changes in the intensity of these processes is showed. A new mechanism of influence is proposed of processing magnetic field on the wear, from which is concluded the appearance of an electronic system with a modified energy level that is resistant to the formation of chemical bonds, causing the adhesion.
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