The martensitic stainless steels are applied in specific conditions due to theirs corrosion and mechanical resistance. The study of these steels after heat treatment is relevant because it may involve the production and development of new steels with better properties for several applications. This study investigates the effect of heat treatment of quenching and tempering in two martensitic steels - 13Cr2Ni0.1C and 13Cr1Ni0.15C (% weight). Dilatometric tests were performed in the samples after melting process in order to obtain the initial and final temperatures of formation of austenite and martensite. The results showed that the quenched samples have the highest hardness and a martensitic microstructure with delta ferrite presence. On the other hand, the samples after tempering showed different matrix suggesting that the martensite decomposition with no change of the delta ferrite.