This paper discusses the results of studies focused on the wear resistance, patterns of wear and plastic properties of Cr,Mo-(Cr,Mo,)N-(Cr,Mo,Al)N coating, containing 20 at.% Mo. The coating had a nanolayer structure with a modulation period λ = 50 nm. The studies revealed the hardness, fracture resistance in scratch testing, as well as elemental and phase composition of the coating. The studies of the tool life of carbide cutting tools with the Cr,Mo-(Cr,Mo,)N-(Cr,Mo,Al)N coating proved their longer tool life compared to that of uncoated tools and tools with the reference Cr-(Cr,Al)N coating of equal thickness and equal content of aluminum (Al). The studies included the comparison of the tools coated with Cr,Mo-(Cr,Mo,)N-(Cr,Mo,Al)N and Cr-(Cr,Al)N. The experiments focused on the specific features of the coating nanostructure and were conducted using a transmission electron microscope (TEM), revealing the different mechanisms of fracture. The penetration of particles of the material being machined between nanolayers of the coating results in interlayer delamination. When exposed to a moving flow of the material being machined, plastic deformation (bending) of the coating nanolayers occurs. The diffusion of iron into the coating (up to 200 nm) and diffusion of Cr and Mo into the cut material to a depth of up to 250 nm are observed. The presented information can help in the design of metal cutting tools and the choice of coatings for them.

One of the limitations of additive manufacturing technology is the high surface roughness of finished products caused by the layered structure of the deposition and the effect of adhesion of unfused powder particles. This worsens the fatigue characteristics, wear resistance, and functional properties of the parts, which are especially important for critical applications in medicine, aviation, and mechanical engineering. The paper presents the results of a study on the possibility of using plasma electrolytic polishing for post-processing of products made of additively manufactured Ti6Al4V alloy to form a homogeneous surface with reduced roughness. The morphology, roughness, and tribotechnical characteristics of the surface after processing in a fluoride electrolyte were studied with varying voltage and polishing time. A 90% reduction in surface roughness is achieved by polishing at 300 V for 20 min. The results of tribological tests revealed that after the polishing of the oxidative wear mechanism is maintained, the temperature in the tribological contact zone decreases, and the load-bearing capacity of the surface increases (the Kragelsky–Kombalov criterion decreases). The greatest decrease in the friction coefficient by 2.1 times was observed with minimal surface roughness, when the largest average radius of rounding of the microprotrusions of the friction track microtopology is formed with a low value of the Kragelsky–Kombalov criterion.

A method of local plasma electrolytic nitrocarburising by the directed action of an electrolyte jet on the side surface of a rotating shaft is proposed. Changes in the structural-phase composition of the surface layer, surface morphostructure and tribological properties in the contact area of the electrolyte with the treated surface and adjacent areas of low-carbon steel are studied. Formation of a gradient of structural-phase changes is shown, which is determined by a change in temperature and intensity of carbon and nitrogen diffusion, as well as the cooling rate during hardening. The competing effect of high-temperature oxidation, the intensity of which is determined by the temperature distribution over the heated surface, and anodic dissolution on the morphostructure and roughness of the surface is determined. Tribological tests have shown the possibility of reducing weight wear by 18.4 times and volume wear by 5.4 times with a decrease in the actual contact area of the rubbing surfaces, which is observed in the heating area center in the presence of a martensite substrate and increased surface roughness. Analysis of the microgeometry of friction tracks showed that deformations in the tribocoupling are not elastic, but plastic and do not transition to the microcutting mode.