(1) The hardened layer of tooth surface has fine martensite structure of grade 2 and non-martensite structure of 0.02mm, which meets the technical requirements.
(2) There are more ferrites (grade 6) in the center. Therefore, although there is martensite structure in the center, the hardness is not high, and the hardness is lower than the lower limit (29HRC test result, 29-46 HRC technical requirement provided by the supplier), which indicates that the quenching cooling capacity is insufficient.
(3) The tooth crown is worn and flaked seriously, the structure is obviously deformed, and the structure at the wear place has undergone phase transition.
(4) The fracture originates from the root and spreads rapidly towards the center.The crack originates from normal carburizing and quenching structure. After fracture, the fracture is partially rubbed and extruded and the structure is deformed.