Surface integrity and bending fatigue behavior of aeronautic gear steel under combined carburized treatment and shot peening

The carburized treatment combined with shot peening were introduced to improve fatigue behavior of aeronautic gear steel. Surface integrity and fatigue behavior after carburizing and combined treatment were systematically analyzed. Results indicated that surface roughness, microhardness and residual compressive stress were increased after combined. Meanwhile, average size of ultra-fine grains was reduced to 0.495 mu m. Fatigue limit was increased from 720 MPa of carburized samples to 890 MPa treated by combined. Moreover, higher shot peening jet presure in combined treatment does not necessarily lead to better fatigue limit. Residual compressive stress was an important factor affecting fatigue cracks propagation mode.

Automated summary

The carburized treatment combined with shot peening was used to enhance the fatigue behavior of aeronautic gear steel. The study systematically analyzed the surface integrity and fatigue behavior after carburizing and combined treatment. The results showed that the combined treatment increased surface roughness, microhardness, and residual compressive stress, while reducing the average size of ultra-fine grains. The fatigue limit of the samples treated by combined treatment was increased from 720 MPa to 890 MPa compared to carburized samples. Additionally, higher shot peening jet pressure did not necessarily result in better fatigue limit. Residual compressive stress was identified as an important factor influencing fatigue crack propagation mode.