Abstract
The causes of dimensional evolution of martensitic steel during the maintaining at a certain temperature are as follows: firstly, the precipitation of carbides starting from the oversaturated carbon from the martensite which provokes o shrinkage and, secondly, the decomposition of retained austenite which induces an expansion due to the evolution of decomposed austenite in function of maintaining time. The presented in this paper have put in evidence the fact that the application of some cryogenic treatments (cooling till –70C) to bearing steel, determining the reduction of quantity of retained austenite till 5% with benefic effects on dimensional stability, wear resistance and contact tiredness, pitting, in general to the fiability of bearings.