Issue 78

M. Bronovets et alii, Frattura ed Integrità Strutturale, 78 (2026) 367-377; DOI: 10.3221/IGF-ESIS.78.21

that can lead to a reduction in energy losses and an increase in the efficiency of mechanisms using rolling bearings. In addition, the tests have shown a several-times increase in the service life of bearings treated with LSP. This finding suggests an enhancement in the reliability and durability of friction units, a critical consideration for applications where equipment failure can result in severe consequences. Based on literature data for similarly treated bearing steels [21, 24, 25], the mechanism of reducing the rolling resistance moment after LSP is hypothesized to be driven by several interrelated factors. LSP is known to increase the microhardness and wear resistance of the surface layer, which reduces wear intensity and prevents the formation of defects on the rolling surface. Additionally, LSP typically leads to the formation of residual compressive stresses in the surface layer, which prevent crack propagation and increase the fatigue failure resistance. The increase in the service life of bearings after LSP is associated with an increase in the fatigue strength and wear resistance of the surface layer. LSP promotes the formation of a more homogeneous and fine-grained structure of the material, which increases its resistance to fatigue failure under cyclic loads. Taken together, these factors lead to a substantial enhancement of bearing life and improved equipment reliability. Study of the surface roughness Fig. 6 shows the profilograms of the initial surfaces of the steel disks, made both before and after the application of LSP. A visual analysis of the profilograms demonstrates a noticeable change in the surface relief after LSP, characterized by an increase in the amplitude and height of irregularities.

(A) (B) Figure 6: Topography of the original surfaces of the disks before (A) and after (B) LSP.

An analysis of Fig. 6 showed that laser shock treatment resulted in a statistically significant increase in the arithmetical mean height (Sa) and maximum roughness height (Sz). Specifically, for the original surface without LSP, the mean square roughness was Sa = 0.28 ± 0.04 µm, while after LSP this parameter increased to Sa = 0.42 ± 0.08 µm. A similar trend was observed for the maximum roughness height: Sz = 18.5 ± 1.2 µm for the untreated surface, and Sz = 42.4 ± 4.5 µm for the surface subjected to LSP. The increase in the surface roughness after LSP is apparently associated with the formation of microrelief under the influence of a shock wave generated by a laser pulse. The shock wave induces plastic deformation of the surface layer, leading to the formation of microprotrusions and depressions, which causes an increase in the parameters Sa and Sz. The obtained results highlight the need for careful control and optimization of laser impact machining parameters for tribological applications. It is known that the surface roughness parameters have a significant impact on tribological characteristics such as friction coefficient, wear resistance, and lubricity. Excessive roughness can lead to increased friction and wear rates, while a too-smooth surface can impair lubricant retention. Fig. 7 and Fig. 8 show the profilograms of the

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