Fracture reason of 20CrMoA steel drive gear

The fracture of a transmission gear occurred during the test run. The fracture reasons of 20CrMoA steel gear were analyzed by means of macroscopic observation, scanning electron microscope analysis, chemical composition analysis, metallographic examination and hardness test. The results show that the gear was characterized by overload fracture. The coarse martensite structure, high hardness and deep effective hardening layer reduced the mechanical properties of the material, which eventually led to the fracture of the gear.