Residual stress depth profiles for vacuum carburized and hardened AISI 9310 steel
Residual stress significantly impacts the fatigue life of carburized low alloy steels resulting in premature failure, making it essential to understand and accurately predict the relationship between case depth and residual stress. The study investigates the influence of case depth (0.014”, 0.026”, 0.050” and 0.066”) on residual stress distribution in 9310 gear steel. The sin2y X-ray diffraction technique is used to determine residual stress depth profiles on samples exposed to different heat treatments and after different steps within the heat treatment sequences including carburizing, oil quenching, cryo-treating, and tempering steps. Residual stress results are compared to hardness and phase assemblage data. Results show that greater case depths result in more gradual hardness transitions from case to core and more uniform hardnesses throughout the case regions. Greater carburization depth generates compressive residual stress following martensite formation. However, during intermediate heat treatment stages, such as carburizing and oil quenching, a high amount of retained austenite remains at the sample surface due to incomplete martensitic transformation. Surface to bulk residual stresses is influenced by microstructural changes at each carburization case depth during intermediate treatments, whereas final tempering exerts minimal impact on the magnitude of these stresses.
Keywords: Residual Stress; Depth profile; Vacuum Carburizing; Case Depth; Heat Treatments
International Conference on Residual Stress
(https://www.asminternational.org/icrs-12/)
Distribution A. Approved for public release: distribution unlimited. (AFRL-2025-1591) Date Approved 03/26/25