Bionics research has revealed the remarkable fatigue resistance exhibited by intertidal zone shellfish, attributed to their radial ribs and multi-layered microstructure. Leveraging the analogous stress and working conditions shared by shellfish and gears, we adopted the discrete laser surface melting (DLSM) technology to create discrete laser surface melted (DLSMed) units on gear tooth surfaces. This paper aimed to scrutinize the influence of discrete laser surface melting on the fatigue performance of 20CrMnTi steel gears. In terms of laser selection, we opted for the Nd: YAG pulsed laser. Across various laser parameters, the proportion of DLSMed units on gear tooth surfaces varied. Scanning Electron Microscopy (SEM) facilitated the observation of microstructures and fatigue morphology of the DLSMed gear. X-ray Diffraction (XRD) measurements gauged residual stress along both the surface and cross section of the DLSMed unit, unveiling the residual stress distribution. Microhardness and surface roughness were assessed through a microhardness tester and a surface profilometer, respectively. Fatigue tests were conducted using both the Forschungsstelle für Zahnräder und Getriebebau (FZG) testing machine and a high-frequency fatigue testing machine. Experimental findings disclosed that the DLSMed unit comprised a melting zone and a heat-affected zone. The depth of the residual compressive stress layer increased alongside current intensity, albeit with the unexpected emergence of residual tensile stress. Enhanced current intensity corresponded to a noticeable elevation in the DLSMed gear's hardness value. Differing fatigue behaviors were evident between the as-received gear and the DLSMed gear. The DLSMed gear exhibited reduced fatigue damage compared to the as-received gear. The DLSMed units effectively curbed crack initiation and propagation, markedly enhancing gear fatigue performance. A direct relationship between the DLSMed unit's area proportion on the gear surface and gear fatigue strength was established. Finally, we delved into the anti-fatigue mechanism underlying the DLSMed gear's performance.
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