Enhanced carbide precipitation during tempering of sub-zero celsius treated AISI 52100 bearing steel

A 1.5%Cr, 1%C bearing steel was sub-zero Celsius treated after quenching. Transmission and reflection (synchrotron) X-Ray Diffraction were applied ex-situ at the HZBBESSYII synchrotron facility to quantify the phase fractions of martensite and austenite and determine the stress state in austenite. The tempering response of the sub-zero treated material was studied with high resolution dihtometry and compared with the behavior of a reference as-quenched sample. X-Ray Diffraction indicates that sub-zero Celsius treating reduces the content of retained austenite in the material and introduces a state of compression in austenite. Dilatometry indicates that a long isothermal holding at cryogenic temperatures enhanced the precipitation of transition carbides during tempering.