Dimensional Stability Analysis of Unconventional Treated Steel Bearings

Abstract

One of the most important characteristics of the element bearings behaviour evaluation is the dimensional stability in time. The structures resulting in conventional thermal treatments are characterized by a major instability along time. Structural changes cause dimensional changes for both austenite and martensite transformations. Residual austenite transformation generates an increase in volume while the martensite transformation decomposes when volume decreases. Research has shown that cryogenic treatment and steel tempering in ultrasonic field applied to bearing steels have a positive influence on the dimensional stability. In what the dimensional stability concerns, the heat treatment below 0°C acts specifically on those sources of strain that have a maximum contribution to further parts dimension modification, especially on the transformation of austenite into martensite. It would have been better if the amount of austenite that remained after quenching at room temperature had been higher and the steel contained more carbon and alloying elements [.