Changes in residual stress state during quench and temper of vacuum carburized gear steel

Vacuum carburizing of 9310 gear steel followed by austenitizing, oil quench, cryogenic treatment, and tempering is known to impact residual stress state of the material. Residual stress magnitude and depth distribution can have adverse effects on part distortion during intermediary and finish machining steps. The present research provides residual stress measurement, microstructural, and mechanical property data for samples taken along a specific heat treat sequence. 4.5” diameter test rings of AISI 9310 steel are subjected to a gear manufacturing sequence that includes normalizing, rough machining, carburizing to 0.03”, austenitizing, quench, cryo-treatment, temper, and finish machining. Characterization of a test ring and a metallurgical sample after each manufacturing step allows tracking of residual stress and microstructural changes along the sequence. Data can be used for future ICME models of the heat treat and subsequent machining steps. Analytical methods include X-Ray diffraction, optical and electron microscopies, mechanical testing, hardness testing, and phase analysis.