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Metallurgical phase transformations in the case layer of a carburized bearing steel due to rolling contact
Abstract
The cone (inner race) of a $6{1\over2}$ x 12 inch tapered roller bearing made from case carburized AISI-SAE 4320 steel had the near surface layers analyzed after 0, 2422, 5432, and 13,413 miles of service. Changes in the residual stress, retained austenite, texture, particle size, and dislocation density were determined by x-ray diffraction techniques. The surface hardness and the inside diameter (bore) were also measured during this investigation and the microstructure of the material was studied for selected samples. The research has shown that retained austenite transformed to martensite in the near surface layers due to the rolling contact forces. The volumetric expansion associated with this transformation caused an increase in the residual compressive stresses and a small increase in the bore diameter measurements. The rolling contact forces also caused the particle size of the retained austenite to decrease and the dislocation density to increase due to work hardening of the softer structure. In addition, the surface hardness increased a corresponding amount. Annealing studies on a reconditioned cone found a decrease in the residual compressive stresses and a decrease in the bore diameter with an annealing temperature of $350\sp\circ$F. Additional work involving regrinding of the rolling surface of a used cone removed some of the residual compressive stresses and caused the bore diameter to increase.
Subject Area
Materials science|Metallurgy
Recommended Citation
Medlin, Dana James, "Metallurgical phase transformations in the case layer of a carburized bearing steel due to rolling contact" (1993). ETD collection for University of Nebraska-Lincoln. AAI9611061.
https://digitalcommons.unl.edu/dissertations/AAI9611061