超高强钢深滚压-预扭复合强化表面完整性研究

In order to improve the fatigue life of ultra-high strength steel under extreme load conditions, the composite strengthening method of deep rolling and two-angle pre-torsion was proposed. The formation of surface integrity and the strengthening mechanism of the microstructure of ultra-high strength steel under the coupling action are revealed by confocal microscopy, electron back scatter diffraction (EBSD), and transmission electron microscope (TEM). It is found that under the composite strengthening, the depth of the reinforced layer of residual compressive stress was improved, and the depth of the deep rolling and 13.7°/7.71°pre-torsion strengthening layer reached 1.2 mm, and an obvious "second reinforced layer" appeared, and the maximum circumferential residual compressive stress is −535 MPa, which appeared at 0.3mm from the surface. The grain refinement and dislocation multiplication in the surface layer are promoted. Compared with the single-angle pre-torsion, the combination of large and small angles pre-torsion after deep rolling reduced the grain size and increased the density of geometrically necessary dislocation. The surface layer microstructure is distributed in a gradient along the depth direction. The effectiveness of the two-angle pre-torsion after deep rolling method is proved, which is of great significance to the development of surface strengthening technology for hard-to-machine ultra-high strength steel parts.