CRACK PROPAGATION STUDIES IN AUSTENITIC STAINLESS STEEL IN HOT CORROSIVE FLUE GASES CONTAINING VANADIUM.

The effect of vanadium content in flue gases on cracking and crack propagation in 304 type stainless steel at 550 degree C has been studied. Kerosene was used as the base fuel and vanadium content was varied from zero to 40 ppm. It has been observed that increasing vanadium up to around 20 ppm reduced the crack initiation time, increased the propagation rate and decreased the threshold stress intensity factor. Beyond 20 ppm of vanadium the trend is slightly reversed, thereby showing that there is a critical value of vanadium content in the flue gases for the worst attack. Cracking has been found to be intergranular. A probable mechanism of cracking and crack propagation is discussed.