After the above experimental analysis and referring to the metallographic inspection of Automobile Carburized Gears, it can be observed that the gear carbides in the experimental samples are grade 1 ~ 3, residual austenite grade 1 ~ 3 and martensite grade 1 ~ 3, and there are a small amount of residual austenite, dispersed fine carbides and high-temperature tempered martensite. There are many free iron elements in the tissue at the center of the sample, which is consistent with the rapid decline in the hardness of the gear root, which is also the main reason for the relatively low hardness of the gear root. During the analysis, it can be found that the fracture reason of aluminum alloy automobile gear is mainly affected by the gear design parameters. If the gear modulus is small, the bending stress at the tooth root increases, resulting in hardness mismatch and peeling. Another factor is the influence of gear material and processing technology. Inclusions, chemical composition and structural segregation in gear material will destroy the continuity of gear matrix and reduce the strength of material. The chemical composition of gear material will affect its hardenability. It is not conducive to obtain martensite during quenching, resulting in stress concentration in the segregation micro zone during heat treatment, resulting in a great reduction in the overall mechanical properties.
Aluminum alloy automobile gears are prone to fracture failure in the working stage, and there are many factors affecting the fracture of gears. To prevent its fracture failure, it is necessary to confirm its fracture phenomenon, factors and failure process. Based on the analysis of fracture morphology and the change of metallographic structure at the fracture, the corresponding fracture factors are obtained. Generally, the fracture failure of aluminum alloy automobile gears is mostly fatigue fracture, and a small part is caused by internal stress and structural factors. Based on the above analysis results, appropriate fatigue removal treatment can be adopted for aluminum alloy automobile gears to ensure the normal operation of aluminum alloy automobile gears and improve the safety of automobile use.