The relevance of this study lies in the need to research the wear process of the elements of dynamic systems and to establish the dependence of the geometric and structural characteristics of wheels restored by plasma surfacing with a coating of 15Cr17Ni12V3F on dynamic, cyclically varying loads. The study was aimed to establish the dependencies between the deviation of the wear area, the formation of contact and fatigue stresses, and the change in the phase structure of the wheel defect. It is important to justify the permissible limits of wear of the transverse profile in the contact zone of a wheel and ridge. The object of the study was the dynamic interaction of the “wheel–ridge–rail contact surface” system. To achieve the goal, the following methodology was adopted: kinematic analysis, strength calculation, the use of mathematical analysis in dynamic system modelling, virtual modelling in the SOLIDWORKS software environment of the GearTrax application, experiment planning, and model correction through the results of metallographic studies. The results of the study are presented as reasonable prediction criteria that consider contact cycles during the formation of fatigue stresses at the stage of defect origin. The process of the dynamic interaction of the contact worn profile of a wheel with a railway rail is explored. Polynomial equations are proposed to substantiate the optimal design and technological parameters of designing a railway carriage wheel. The permissible limits of wear of the transverse profile in the contact zone of the wheel and the ridge are justified while taking the coefficient of the reduction of contact stresses in the metal into account. The dependences of the change in static load on the utilization factor of the railway carriage load capacity are established. The dependences of changes in fatigue stresses on the design deviation of the contact area of wheel wear are established. It is confirmed that the stress concentration under cyclic loads is formed in the ferritic layers of the material structure before the appearance of wear.

The scientific article is devoted to the study of modern technologies for restoring the internal surfaces of critical parts of the structural elements of oil and gas pumps. By the method of critical analysis of defects, it was found that paraffin deposits and mechanical impurities are in the list of the main complicating factors leading to abrasive wear of the working surface of the parts being contacted. Asphalt-resin-paraffin deposits together with mechanical impurities are distributed unevenly, for example, along the diameter of the cylinder of the injection column, narrowing the passage section of the rod in different stroke length intervals. This phenomenon causes the rod to deviate from the design axis of the trajectory of movement and forms sections of the cylinder working under shock loads with maximum wear. Therefore, it is necessary to restore the degraded surface in places where maximum dynamic loads are applied. The patent search method and the evaluation of the claims allowed us to establish that the generally accepted methods of restoring internal surfaces are reduced to nitriding and chrome plating. Due to known technological shortcomings, these methods are limited in application, and it is impossible to restore the phase structure by these methods. To solve the technological problem of restoring the structure and modifying the inner surface of a small cylinder diameter, it is proposed to apply a coating with a ceramic protective layer based on nickel alloys of the carbide class, which has high hardness and inert properties. To restore the surface of worn parts in conditions of a limited coordinate space of long-dimensional elements of the RDP structure (pump and compressor pipes, a pair of cylinder-plunger and others), the authors propose a promising laser spraying.

A unique controlled laser head with an adaptive module was developed to stabilize the trajectory of movement. The scientific and practical problem of developing a technology for restoring the inner surface of a small diameter up to ∅44 mm was solved by the introduction of a laser head. Adhesion was achieved by moving the laser along the vectors, forming a regular pyramid with opening angles at the top. High physical and mechanical properties of the restored pump surface were achieved by the laser technology when spraying powder composition 15Cr17Ni12V3F35ZrO2. The optimal values of the microhardness of the coating of 5000 MPa were achieved due to the optimal transition melting zone of 0.8 ÷ 1.45 mm; the laser radiation power density of 3 × 105 W/cm2; and the diameter of the focus spot of the laser beam of up to 1.3 mm. High corrosion resistance and tribology were achieved by an optimally matched distance of 10 ÷ 15 mm and a surfacing speed of 15 mm/s. Homogeneous spheroidized particles of the material were observed in the martensitic phase of the structure. The stable compression stresses in the phase structure during the laser deposition of zirconium dioxide were fixed at the level of 1.0 ÷ 1.5 N/m2, and the compression stresses were at the level of 0.2 ÷ 0.4 N/m2. A multifactorial experiment established the dependence of the coating hardness on the distance to the focal plane and the energy characteristics of the laser source, providing optimal laser parameters (area, pulse power, and duration).

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