Decarburization-controlled internal oxidation of rolling bearing steel SAE 52100 at the dissociation pressure of wustite

Incomplete internal oxidation of rolling bearing steel SAE 52100 in Rhines pack consisting of Fe2O3 and Fe powder was applied to determine the permeability for oxygen, at the dissociation pressure of wustite, between 1073 and 1373 K. Simultaneous rim decarburization permitted the examination of ferritic and austenitic base material and the ascertainment of the influence of the alpha-gamma phase transformation on the oxidation rate. The narrow transition range at around 1170 K is characterized by oxygen partly diffusing in ferrite and in austenite. Bulk diffusion of oxygen was found to be the main transport mechanism. The slight preceding of grain boundary oxidation diminishes with increasing temperature in both investigated iron phases. The permeation constants of ferrite and austenite for oxygen, in equilibrium with wustite, can be described by Arrhenius-type equations. From these expressions, the solid solubilities of oxygen in ferrite and austenite were derived by inserting literature data on the concerning diffusivities. These results are comparable with literature data published previously. Incomplete oxidation of alloying elements due to the formation of protective oxide layers around precipitated particles and accelerated oxygen diffusion along metal/ oxide phase boundaries may raise the deduced permeability for oxygen.