E. Feldshtein

Improving the efficiency of running-in for a bronze–stainless steel friction pair

In this paper, the possibility of the transfer of additives that are in the emulsion mist is shown by the example of the bronze CuSn7Zn4Pb6–stainless steel X10CrNi18-8 friction pair. The additive is first transferred on the processed surface of the part and through it–in the contact zone of the friction pair. It was established that the emulsion mist reduces the roughness of machined stainless steel surface more than three times, and the introduction of additives based on phosphate esters into the emulsion reduces the roughness by 4–4.5 times. Phosphate-based additive remains on the machined surface in significant quantities, even after 30 min working at heavy loads, reducing the instantaneous friction coefficient and the temperature of the friction zone. The mean width of profile elements of the assessed profile of bronze samples decreases by two times and their bearing length ratio decreases by four times. In this case, a decrease in the wear rate of bronze by more than 40% is ensured. This fact indicates the better running-in of the friction pair.

Research on emulsion mist generation in the conditions of minimum quantity cooling lubrication (MQCL)

The paper presents the effect of emulsion mist generation parameters and the distance of the nozzle from the contact zone of the cutting wedge with the workpiece on the diameter and number of droplets supplied into the cutting zone. The conditions of emulsion mist generation, in which all the droplets supplied to the cutting zone in a given time, are evaporated in this time. An analysis of heat flow in the MQCL method was presented and it was proved that the air flow and the distance of the nozzle from the cutting zone have the most significant effect on the diameter of droplets.

Tribological behavior of sintered tin bronze with additions of alumina and nickel oxide

The tribological characteristics of sintered tin bronze with additions of oxides of aluminum and nickel have been studied. The addition of ultrafine particles of alumina or the mixture of alumina and nickel oxide to sintered tin bronze reduces the coefficient of friction, the temperature in the friction zone and the volume wear rate of the rubbing surfaces. The average coefficient of friction of the material does not change substantially over time. During wear, the chipping of oxide microparticles was observed, which led to a change in the roughness of the working surfaces. The presence of Motor Life Professional additive in oil reduces coefficient of friction, the temperature in the friction zone, and the volume wear rate of rubbing surfaces.

Tribological characteristics of hardened-and-tempered structural steels turned by inserts covered with multicomponent PVD coatings

The effect of coatings deposited on cutting tools using the PVD method on the tribological characteristics of the surface layer after the finish turning of 41Cr4 and 30CrMnSi steels is considered. The tribological characteristics of the turned surfaces change substantially. The best results are achieved when using the (AlTi)N coating, which ensures substantial decreases in the coefficient of friction (by 35–40%) and the temperature in the friction zone (by up to 30%). The dependences of the wear on the friction path are linear; the wear rate of the surfaces turned by the coated tools is significantly lower than that for the surfaces turned by the uncoated tools. Compared to the uncoated R25 hard alloy, the difference in the wear rates reaches 60% in favor of (AlTi)N and (TiAl)N coatings. A decrease in the thickness of the coating from 4 to 2 μm leads to a growth in the coefficient of friction and the temperature. An X-ray structural analysis of the surface layers of the turned specimens has revealed the presence of Fe-Al solid phases, which improve the wear resistance of the surface and the efficiency of coatings like (AlTi)N.

Modeling of the thermal field of a workpiece in milling of austenitic steel by a finger-type cutter

The authors report results of modeling thermal fields by the method of finite elements under conditions of milling of 00H17N14M2A austenitic steel by a finger‐type cutter. A solution of the problem of unsteady nonlinear heat conduction has made it possible to find the temperature distribution in the surface layers of a workpiece as a function of the cutting rate and the position of the tip of the cutter edge.

Forces and Process Dynamics in Profiling of AlCu4MgSi Aluminium Alloy

This work presents the results of experimental research regarding cutting force, chatter frequency and amplitude for different cooling conditions in profiling of AlCu4MgSi aluminium alloy. The following conditions were analyzed: dry cutting, cooling with water-based emulsion, MQL and MQCL. It was determined that cooling and lubricating conditions in the cutting zone have a minimal effect on machining forces in the following range of parameters: cutting speed 300–600 m/min, depth of cut 1–2 mm, feed rate 0.1–0.5 mm/rev. Therefore, a conclusion to introduce dry machining to cut down costs was formed. Changes in cutting force components can be described by the following relation: Fc ≈ Fp > Ff. The intensity of the effect of technological parameters on cutting force components decreases in the direction of f → ap → vc. It was proven that by analyzing changes of cutting force in machining time, possibilities of chatter occurrence for different machining conditions can be assessed.

On the Formation Features and Some Material Properties of the Coating Formed by Laser Cladding of a NiCrBSi Self-fluxing Alloy

In the present paper, the influence of laser cladding conditions on the powder flow conditions as well as the microstructure, phases, and microhardness of a Ni-based self-fluxing alloy coating is studied. The formation regularities of a coating microstructure with different cladding conditions as well as patterns of element distribution over the coating depth and in the transient zone are defined. The microhardness distribution patterns by depth and length of a coating for various laser cladding conditions have been studied. It was found that the laser beam speed, track pitch, and the distance from the nozzle to the coated surface influence the changes of the coating microstructure and microhardness.

Effect of Copper Content on Tribological Characteristics of Fe−C−Cu Composites

The paper presents the results of an investigation of the effect of the copper content on the tribological characteristics of Fe−C−Cu composites. It has been shown that the best tribological properties and hardness are shown by material containing 3% copper. In the case of a 10% copper concentration, the wear rate of the composite rises by as much as ten times, while at a 20% concentration, it decreases. It has been proved that the copper concentration significantly affects the formation of friction surface morphology.

On the Effect the Iron Content on the Tribological Properties of Sintered Tin-iron Bronze

The effect of iron content on the strength and tribological characteristics of sintered tin-iron bronzes has been studied. It has been shown that the porosity has been reduced and the hardness monotonically increased with an increase in the iron content of the material. The strength dependence of the iron content is nonmonotonic, and the maximum strength increase took place at the iron content of 5%. The minimum coefficient of friction, the temperature in the friction zone and wear rate have been observed at iron content of 5–10%. In this case, the micropores and microlacunes have been formed on the friction surfaces that provide better lubricate conditions for the friction surfaces.

On the Bonding Strength of Fe-Based Self-Fluxing Alloy Coating Deposited by Different Methods on the Steel Substrate

Abstract In the present paper, the bonding strength of Fe-based self-fluxing alloy coating deposited by plasma spraying, gluing and laser remelting and alloying on the steel substrate have been investigated. When flame melting, a globular structure is formed. Against the background of the solid solution carbide-boride phases are clearly distinguishable, between which the Fe–Fe2B and Fe–FeB eutectic colonies are situated. Laser remelting leads to the formation of metastable structures, reinforced with dendrites, consisting of alloyed Fe-α and Fe-γ. At the low laser beam speeds the coating is melted completely with the formation of a cast structure with the dendrites. When the laser beam speed is increased, the dendritic structure gets fragmented. Structures of coatings alloyed with B4C and remelted by the laser beam vary with the increase of the spot speed. The bonding strength of coating without subsequent remelting decreases by 4–5 times in comparison with remelted. The bonding strength of the reinforced glue coating has adhesive and adhesive-cohesive character. When the load increases in the coating, microcracks develop, which gradually spread to the center of the bonding surface. For plasma coatings after laser remelting without additional alloying, the maximum bonding strength is observed with the minimum laser beam speed. With increasing the laser beam speed it decreases almost 1.5 times. In glue coatings reinforced with B4C particulates by laser remelting, the bonding strength is lower by 1.2–1.4 times in comparison with plasma coating.