SOME ASPECTS OF TEMPERED MARTENSITE EMBRITTLEMENT IN 3CR-MO-V STEEL

The paper deals with the tempered martensite embrittlement phenomenon in the low-carbon low alloy 3Cr-Mo-V steel tempered in the temperature range of 523-773 K. To determine the tempered martensite embrittlemen t the Charpy-V test at the temperature 223 K was performed. The method s of light microscopy, transmission electron microscopy (TEM) scanning electron microscopy (SEM) and hardness testing (HRC) were applied. In temperature dependance of CVN the minimum at 623 K was found to exist . The mechanism of transgranular cleavage corresponding to a transgran ular mode of the tempered martensite embrittlement was found out durin g the failure. In the microstructure of the quenched states the retain ed austenite around the martensitic laths as well as the fine carbide particles inside the laths were observed. This can be considered as a cause of the transgranular mode of the tempered martensite embrittleme nt. The difference in grain size (0.1-0.8 mm) affects the tempered mar tensite embrittlement of steel only weakly.