Study on the Microstructure and Texture Evolution of Hot Forged 20CrMnTiH Steel Spur Bevel Gear by Simulation and Experiment

Due to the non-uniform dynamic recrystallization (DRX) and deformation behavior during hot forging process, the spur bevel gears tend to receive heterogeneous microstructure which greatly affects their mechanical properties and service life. Therefore, the aim of this study is to investigate the evolution of microstructure and texture of hot forged 20CrMnTiH steel spur bevel gear utilizing both simulation and experiment method. In the present study, a sound finite element model of hot forging of a 20CrMnTiH steel spur bevel gear was developed under the Deform-3D software. The experimental analysis was conducted by employing scanning electron microscope, electron backscatter diffraction and transmission electron microscope. The simulation results indicated that the grain size, effective strain and DRX volume fraction were inhomogeneous from the surface region to the core region of gear tooth. The experimental analysis revealed that the surface region of gear tooth possessed the strongest γ-fiber and lowest dislocation density. However, both subsurface and core regions had a combination of moderate α- and γ-fibers, and large amount of dislocations pinned by precipitates can be observed in these two regions. Furthermore, the microhardness exhibited parabola distribution through the gear tooth, and the subsurface region possessed the largest microhardness value.