Vol 39, No 4 (2018)

Analysis of the ways of improving the inductive method for diagnostics of the wear of tribological assemblies by the wear debris and the current state of the developments of inductive particle counters is performed. It is shown that the inductive counters based on the phenomenon of mutual electromagnetic induction that use three volumetric coils are applied to diagnose heavy loaded assemblies; however, in virtue of their restricted sensitivity to fine particles with sizes below 100 μm, the counters in question are not applicable to early diagnostics of the wear of tribological assemblies that operate under medium load and speed rates. To control the condition of the above assemblies, multichannel inductive counters can be used fitted with double-layer planar coils that record ferromagnetic and non-ferromagnetic wear debris with sizes of ≥75 μm. It is demonstrated that to date the highest sensitivity to ferromagnetic wear debris with sizes of ≥11 μm has been achieved in inductive counters the sensing coils of which have cores. The prospective application of such counters is the control at the early stage of wear of assemblies manufactured of ferromagnetic materials.

A mechanical model of friction and wear of an elastic coating against a wavy punch under forced oscillations (vibrations) is proposed. The model allows predicting reduction in the effective coefficients of friction and wear depending on the parameters of forced vibrations and waviness of the punch. Qualitative agreement between the obtained theoretical dependences and known experimental results is demonstrated. The proposed model can be used for correct interpretation of the results of tribological experiments.

In this paper, we presented studies of the sliding friction without lubrication of Hadfield steel, ShKh15 bearing steel, and AISI steel 1020 against AISI steel 1045 upon applying an electric current with a contact density higher 100 A/cm². We showed that the intensity of the surface layer deterioration increased with increasing current density. The catastrophic wear of materials begins at different values of the current density and at close values of the wear energy intensity. The dependences of the average contact temperatures on the current have been determined. The major conclusion is that it is impractical to harden the primary structure by alloys to achieve a low wear rate.

The structure and the elastic stress in wear tracks of doped titanium nitride coatings with a columnar structure were studied using the methods of transmission electron microscopy. A different character deformation of the coatings was shown depending on the strength properties of the substrates. Effects of modification of a defect microstructure were established on the scales of several columnar grains and in individual nanosize fragments. An increase in the bending–torsion value of the crystal lattice and local stresses was shown in comparison with the state after deposition. The formation of tribofilms with different structure and phase composition was found.

An effect of schungite exerted on the degradation of surfaces in the processes of friction and wear is studied. The process is simulated via processing a mixture schungite and iron powders using a high-energy ball mill. Changes in the morphology and structural and phase composition of the milled mixture, as well as in the surface of the grinding balls, are investigated. It is shown that the positive effect of schungite addition to lubricating substances is mainly caused by improvement of the surface quality (roughness reduction) of the contacting bodies after mechanical treatment.

The article proposes a method to improve adhesion of the wheels to the rails of the railway carriage by means of supply of abrasive loose materials as an alternative to quartz sand to the zone of their contact: metal scale (Fe₃O₄) being the waste of rolling and forging, as well as the iron oxide—magnetite (FeO · Fe₂O₃) of the natural origin. The comparative assessment of efficiency of use of scale and magnetite was carried out in relation to quartz sand traditionally used for railway transport. The adhesion coefficient and wear intensity are used as comparison criteria.

Ecologically clean lubricants as well as bio-based lubricating grease with nanoparticle and other additives belonging to the new class of “green lubricants” are studied. The results of tallow-based lubricant composites modified by functional additives and nanoparticles of thermally expanded graphite and graphene are presented. Improvement of tribotechnical characteristics of lubricant composites in comparison to basic lubricants via addition of nanoparticles is determined.

The possibility of increasing the abrasive wear resistance of tool steels by obtaining a multiphase structure including tempering martensite, carbides, and metastable austenite undergoing dynamic deformation martensitic transformation (DDMT) under abrasive action is shown.