Predicting Distortion and Residual Stress In a Vacuum Carburized and Gas Quenched Steel Coupon

Predicting Distortion and Residual Stress in a Vacuum Carburized and Gas Quenched Steel Coupon A. M. Freborg, B. L. Ferguson and Z. Li Aerospace transmission components are typically manufactured from high strength, case carburized alloy steels such as AMS 6308 (PyrowearŪ53). The combination of carburization and quench hardening of these steels produces residual compressive surface stresses and high surface hardness, thus enhancing both surface durability and fatigue resistance. The hard case, coupled with a tough non-carburized core, provides the foundation upon which additional processing can further improve surface fatigue response. An internal state variable (ISV) material model for carburized and heat treated gear steels has been implemented in the DANTE heat treatment simulation code for the purpose of engineering microstructural, residual stress and distortion response to meet specific steel component application requirements. This paper describes the use of heat treatment simulation to engineer residual stress and distortion response in an AMS 6308 alloy steel coupon to subsequently be used for fatigue testing. The criticality for accurate use of process-descriptive boundary conditions is presented in the context of vacuum carburizing and gas quenching. Model predicted residual stress and distortion response for a tapered, notched coupon are validated against x-ray diffraction and dimensional physical testing.