Texture Evolution Mechanism in the Secondary Tempering Zone of 12Cr2Ni4A Aviation Gear Steel During Rectangular‐Spot Laser Quenching

Laser quenching technology is widely applied in the aerospace and defense industries for surface strengthening of high‐performance steel components. However, multiple overlapping processing often leads to the formation of local softened zones in the secondary tempering zone, and the crystallographic mechanisms of grain orientation evolution and lattice distortion remain insufficiently clear. In this study, a disc‐type laser system was used to perform rectangular point laser quenching treatment on 12Cr2Ni4A aviation gear steel. The morphological evolution characteristics and local softening behavior were characterized through electron backscatter diffraction, polar plots, inverse polar plots, orientation distribution function, scattering topological analysis, scanning electron microscopy, and microhardness testing. The results show that laser quenching promotes the transformation of grain orientation from a dispersed distribution to a concentrated structure dominated by the enhanced (110) related components. In the second tempering zone, the repeated thermal cycling results in a significant enrichment of the A1 grain structure, an expansion of anisotropic orientation scattering, an increase in the proportion of low‐angle grain boundaries, and a decrease in local hardness. It reveals the phenomenon of cumulative lattice distortion and residual stress concentration in overlapping areas, providing a crystallographic basis for optimizing laser quenching processes and enhancing the reliability in service.