Effect of hot corrosion on the creep properties of types 321 and 347 stainless steels

Problems caused by hot corrosion and creep damage on superheater and reheat er tubes of power plants using heavy oil as fuel inhibit the continuous ser vice of the boilers and shorten their design lives. The acceleration of hot corrosion attack of boilers is caused by the presence of fuel ash deposits containing V, Na, and S, in the form of Na2SO4 and V2O5, which form low me lting point phases. In addition to this, the tubes are exposed to the actio n of both high stresses and high temperatures, producing a continuous plast ic deformation of the tube walls called creep damage, Creep rupture tests w ere carried out in the temperature range 620 to 670 degrees C in static air in the presence of corrosive environments using 321H and 347H type stainle ss steels used in superheater and reheater tubes under hot corrosion and cr eep environments. The corrosive environment includes synthetic Na2SO4, V2O5 , and the mixture 80%V2O5-20%Na2SO4. Also, the role of the different elemen ts present in the environments on corrosion was investigated using electron ic microscopy and x-ray diffraction techniques.