A new understanding of micromechanism analysis of gear interference fit failure

To address the problem of macroscopic gear shaft matching caused by the micro deformation of sprocket hole in high-speed railway during in their service, the microstructure of the gear before and after operation was analyzed in detail by means of electron back scatter diffraction (EBSD) and transmission electron microscopy (TEM). Cyclic stress-induced dislocation motion in martensite triggered the transformation of sub-grain boundaries into high-angle grain boundaries (HAGBs), forming new grains and leading to surface layer grain refinement. Volumetric contraction under compression, driven by grain boundary proliferation, amplified surface defects and reduced interplanar spacing, collectively contributing to gear shrinkage. These findings demonstrate that enhancing external stress resistance can be achieved through grain refinement and increased grain boundary obstruction to dislocation motion.