The process of nucleation of fatigue defects in metal alloys with different structural morphology is considered. A physical model was built, calculation expressions were presented, a numerical experiment was performed to determine the moment of nucleation of the critical-size defect in Fe-based alloys during high-speed droplet impacts. The physical model is based on the theory of dislocations. It is shown that the determining factor in the process of wear nucleation under dynamic cyclic loading has a structural factor. Depending on the structure and properties of the material, as well as on the nature of the loads, the critical fatigue defect develops in the form of cracks, pores or microcraters. Comparative data of calculations and bench tests for droplet impingement erosion were presented. The contribution of the nucleation stage during the incubation period of erosive wear of the materials studied was evaluated. Due to the fact that rigorous instrumental methods for determining the duration of the nucleation stage are absent, the usage of the proposed analytical model is recommended for this purpose.

The work is devoted to the study of the phenomenon of grain boundary slippage (GBS) in the ARMCO pure iron at the periphery of the laser treatment zone. Using optical metallography and high-resolution scanning electron microscopy (SEM), the characteristic features of the GBS mechanism were revealed: stepped boundaries, accommodation zones, and grain rotation. It was found that under laser irradiation in the heat-affected zone, the plastic deformation of the ferrite matrix is ​​fully realized by the GBS. Slipping of boundaries is carried out under conditions of ultra-high-speed heating of the ferrite matrix not lower than 700 °C, and the degree of deformation by the GBS mechanism does not exceed 5-6%.

The paper discusses coatings of different composition and structure. The object of the study was the stage of nucleation wear of the coatings. Coatings up to 10–12 μm thick were obtained by ion-plasma deposition in a vacuum. The analytical part of the work is based on the theory of dislocations. This made it possible to create a computational model of the stage of nucleation of wear under conditions of cyclical impacts, which is problematically identified by instrumental methods. The comparison of calculated data with experimental data are given.

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