Abstract：The abnormal failure fracture active bevel gears (for the control of steering during automobile driving) was analyzed in detail by macroscopic fracture morphology observation, elemental spectrochemical composition analysis, metallographic microstructure analysis, non-metallic inclusion analysis, surface and matrix hardness test, surface hardening layer depth determination. The results showed that there was deep non-martensitic structure on the surface of the gear tooth, which reduced the surface hardness and wear resistance of the tooth and the overall fatigue limit of the gear. The fatigue crack source started from the grain boundary or the stress concentration area of the oxide, and expanded rapidly along the grain boundary, which eventually led to the fracture of the gear surface and seriously reduced the bending strength of the gear tooth.
2023, Vol. 41 
