Effect of retained austenite on steel 52100 in different cycles of hardening and mechanical properties

Retained austenite is one of the unfavorable structures during heat treatment of steels which cause to reduce the mechanical properties. In this research the alloy steel of SAE 52100 was used and 5 different heat treatment cycles was applied. The retained austenite measured by XRD set ,then samples were taken under tensile and hardness test and micro structure result of each cycle and fracture cross-section of sample were studied by optical microscope and SEM. The results show that quenching in liquid nitrogen can results in minimum retained austenite percentage about 0.5% and consequently cause to increase the strength and toughness of samples. Also it showed that if even hardness is over 60 HRC, it doesn’t make any grinding cracks. It has been demonstrated that the maximum of occurs as a combination of the increasing carbon concentration in the austenite and of the decreasing volume fraction of the austenite at 250º C.

Keywords:

XRD , 52100 , hardness , structure , Retained Austenite