Study on the Effect of Laser Shock Peening Parameters on the Wear Performance of 55SiMoVA Bearing Steel

Abstract

The wear performance of 55SiMoVA bearing steel under extreme service conditions in oil and gas screw drilling tools is critical to the reliability and operational lifetime of thrust ball bearings. In service, these bearings experience severe friction between the balls and raceways, leading to accelerated wear and even catastrophic failure. Conventional surface modification techniques, such as carburizing, nitriding, shot peening, or surface coatings, provide limited improvements in surface properties and often fail to sustain high-load, high-temperature, and complex lubrication environments. Laser shock peening (LSP) has emerged as an effective surface engineering technique capable of inducing deep compressive residual stresses and forming a hardened surface layer, thereby enhancing both mechanical and tribological performance. In this study, 55SiMoVA steel specimens were treated using LSP with systematically varied process parameters, including impact energies of 4 J, 5 J, and 6 J, and impact numbers of one and two. The effects of these parameters on surface microstructure and mechanical properties were evaluated through surface roughness measurement, microhardness profiling, and X-ray diffraction-based residual stress analysis. To assess tribological behavior, reciprocating linear ball-on-block wear tests were conducted under lubrication with oil-based drilling fluid, simulating realistic service conditions. The results demonstrate that LSP markedly alters the surface and near-surface characteristics of 55SiMoVA steel. The maximum microhardness increase reached 17%, compressive residual stress exceeded 823 MPa, and the hardened layer extended to a depth of 1.3 mm, with a gradual stress gradient from surface to substrate. Single-impact treatments showed limited improvements in friction stability, whereas double-impact treatments significantly stabilized the coefficient of friction and enhanced wear resistance. Among all parameter combinations, the 5 J × 2-impact treatment exhibited the most favorable performance, reducing wear volume by approximately 15% compared to untreated specimens. Microscopic analysis of worn surfaces revealed that untreated samples displayed severe plowing and material spalling, while optimally treated samples exhibited relatively uniform and shallow wear tracks, indicating improved surface integrity. Overall, the study confirms that appropriate selection of LSP parameters can effectively enhance the surface hardness, residual compressive stress, and hardened layer depth of 55SiMoVA bearing steel, thereby significantly improving its wear resistance under lubricated conditions. These findings not only provide a practical surface engineering strategy for extending the operational lifetime of thrust ball bearings in screw drilling tools subjected to extreme and complex conditions, but also contribute to a broader understanding of LSP-induced surface modifications for high-strength alloy steels. The insights gained from this work offer valuable guidance for optimizing LSP processing parameters to achieve superior tribological performance and mechanical reliability in demanding industrial applications.