Influence of heat treatments on the intergranular corrosion resistance of the AISI 347 cast and weld metal for high temperature services

Stabilized austenitic stainless steels such as AISI 347 can be selected to high temperature services due to the high creep resistance of austenite phase. Niobium is added to form fine NbC carbides, which increase the creep resistance and prevents intergranular corrosion. AISI 347 wires and electrodes are frequently used as feed metal to weld AISI 321 and 347 whrought plates. In the present work, we studied the intergranular corrosion resistance of cast structures of AISI 347 steel using electrochemical potentiodynamic reactivation tests. The study applies to cast and weld metal structures subjected to high temperature usage. The solution and stabilization treatments were evaluated. It was found that the solution treatment at 1100 °C followed by stabilization in the NbC precipitation range of temperature is of fundamental importance to avoid sensitization.