Vol 39, No 1 (2018)

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.

The research results on the wear of cutting tools made by sintering high-speed steel powders have been presented. It has been shown that powder tool materials based on high-speed steel additionally alloyed with titanium carbide have high wear resistance and can be classified as a new class of self-organized tool materials. As has been shown by the research, the wear resistance of these tools is 2–3.5 times higher than the wear resistance of standard high-speed steel tools.

The use of characteristics of the contact stiffness in the scientific literature to describe a discrete contact between machine components under normal and tangential loading has been analyzed. The application of a model of the discrete contact of rough surfaces, as well as the influence of the parameters of the contact surface microgeometry on the contact stiffness under normal and tangential loadings and shear has been studied.

The results of tests of a Zr–Al–B boundary friction detonation coating in a wide range of changes under friction conditions have been presented. A comparative analysis of the obtained characteristics of friction and wear in order to evaluate the tribotechnical properties of amorphous-crystalline coatings has been carried out. These results have been compared with parallel tests of coatings based on tungsten carbide, samples of hardened steel and bronze, and the bearing of the sliding layer. The formation of solid solutions has been established and the introduction of oxygen in zirconium that corresponds to the formation on the friction surfaces of the secondary structures of the first type, a characteristic feature of which is their surface localization, ultra-dispersed structure, and ability to minimize disruption and shield unacceptable adhesion phenomena. The use of the Auger electron microscope confirmed that oxygen completely replaces the sulfur in the surface structures.

In this work, the method of forming an exact automodel solution of a problem of hydrodynamic calculations of the wedge-shaped support (a ram and guide) working in the presence of lubricant and the melting of a guide taking into account the dependence of the viscosity of the lubricant on pressure has been given. Based on the equation of the movement of viscous incompressible liquid for a thin layer, an expression has been obtained for the speed of the dissipation of the energy analytical dependence for the profile of the melted guide surface taking into account the dependence of the viscosity of lubricant on pressure. In addition, the main performance data of the considered couple of friction have been defined. An assessment has been carried out of the effect of the parameter due to the melting of the guide and a parameter that characterizes the dependence of the viscosity of the lubricant on the pressure, load-bearing ability, and friction force.

The motion of a solid body across a horizontal plane with asymmetric orthotropic friction has been studied. The direction of the velocity of the center of mass and its distance to the instantaneous velocity center have been determined for the moment of time immediately before the body stops. It has been shown that, upon the initial pure rotation, the instantaneous acceleration of the center of mass begins the in-plane parallel motion. In the case of initial forward movement, its character does not change.

The results of analytical and experimental studies of the microstructures of the welded layers of the Hadfield steel (basic and alloyed with Cr, Ni, Mo, and B) have been presented. Layers additionally reinforced by coarse-grained tungsten carbide have also been studied. It has been shown that an austenitic microstructure prevails in the base and alloyed Hadfield steel. Analytical investigations of the coating structure shows the formation of 95–99% austenite and, in the case of the reinforced phase, the austenite content is 50–56% of the material (the remainder is tungsten carbide, cementite, etc.). It has been found that the presence of the strengthening phase of coarse-grained tungsten carbide, which reduces the amount of austenite under the conditions of abrasive wear, may exert both positive and negative impact on wear.