The effect of nickel on sulphidation resistance of austenitic heat resistant alloys

A series of austenitic heat resistant Fe-Ni-Cr-Al alloys with different nickel contents have been investigated at 1100 degrees C and 25, 50, 50,100 hours in S/O bearing atmospheres. Before sulphidation test, the specimens were annealed in argon at 1250 degrees C for 8 hrs. Weight changes were measured using an automatic then-no gravimetric analyzer and corrosion products were analyzed by scanning electro microscope (SEM), energy dispersive X-ray spectrometry (EDAX), X-ray diffraction and optical microscope. The results showed that sulphidation resistance decreased with increasing nickel content. Internal sulphidation controlled by gaseous transport through cracks and pores and the formation of internal sulphide increased when liquid sulphides formed on the surface.