Residual Stress predictions for Carburizing and Heat Treating AISI 9310 Gear Steel

The magnitude and depth of residual stresses in AISI 9310 gear steel are affected by vacuum carburizing and subsequent heat treating processes. Residual stress distribution can have adverse effects on part distortion during final machining and potentially cause premature part failure in service. Understanding residual stress development throughout the heat treatment process can enable better control of the final residual stress state. Microstructure, mechanical, and thermal properties were characterized and compared to residual stress measurements (using sin²Ψ method). Samples of AISI 9310 steel underwent a representative gear manufacturing sequence that includes normalizing, vacuum carburizing to four different case depths, austenitizing, oil quenching, cryo-treatment, and tempering. Results indicate residual stress state has a partial correlation to the case depth after each thermal processing step. Residual stresses at the surface were dependent on the microstructural changes of each case depth in the intermediate heat treatment steps. The final tempering step, however, did not show a large variation in magnitude of surface residual stresses. The data generated in the current study is compared to finite element simulations using Abaqus and Dante Solutions predicting residual stress distribution in similarly heat-treated parts.

Distribution A. Approved for public release: distribution unlimited. (AFRL-2021-2808) Date Approved 08-24-2021.