The austenitic stainless steel high alloyed (22Cr-25Ni-7Mo-0,3N), well known as superaustenitic, has as its main characteristic a high corrosion resistence to several environments, mainly in sea water. Furthermore the material shows good mechanical properties and thermal stability. To obtain the mentioned characteristics, the material must be thermically treated, taking into consideration the solubility of the alloy elements. Various heat treatments were performed in this research: solution heat treatment (from 1100 to 1250 degrees C), stress relief (from 500 to 800 degrees C) and sensitization (900 degrees C, varing the time at 1, 5h, 12h, 24h and 48h). Hardness and charpy tests were used to study the mechanical behaviour, and optical methalography was done to investigate the heat treatment influence in the material micro structure. It was observed-that even with the solution at an extreamely high heat treatment temperature (1250 degrees C), it was not possible to dissolve the precipitates formed during solidification scattering in the austenitic matrix. To maximize the energy absortion impact, the solution heat treatment must be performed between 1150 degrees C and 1200 degrees C and the stress relief until 500 degrees C. In the 900 degrees C temperature range, the material impact resistence (measured at environment temperature) decreased from 25J to 7J when the heat treatment time was increased from 1, 5h to 48 h.601155161