Influence of stabilization heat treatments on microstructure, hardness and intergranular corrosion resistance of the AISI 321 stainless steel

The AISI 321 is an austenitic stainless steel which contains Ti as stabilizing element. This material can be selected for high temperatures services due to its high creep and intergranular corrosion resistance. However, for services into the sensitization range of temperatures (450– 850 C), the steel must be previously heat treated at higher temperatures for TiC precipitation. In the present work the importance of this so-called stabilization treatment, and the best range of temperatures for its realization, were investigated by means of microscopy and electrochemical potendynamic reactivation tests. It was found that the higher temperature for stabilization must be 950 C. Samples stabilized at 975 C or 1000 C and aged at 600 C for 100 h showed the very begin of the sensitization process.