Influence of Ti, Mn,Nb on the Protection of Preformed Oxide Scale of An Fe-25Cr Alloy in the Sulfidation Environment

An investigation on the influence of moderate amount of Ti(4%), Mh(9%) or Nb(8%)(mass fraction) on the protection of prefromed oxide scale of an Fe-25Cr alloy has been carriedout. It has been found that protective sulfidation behaviour appeared in the sulfidation of all alloys after their preoxidation in 10⁵ Pa (O₂) at 1 000℃ for various time and, afterwards, rapid weight-gain took place. A thicker scale composed of TiO and TiCr₂O₄ mixtureformed on the 4%Ti containing alloy, resulting a twice longer protective period than Fe-25Cr. A porous oxide scale composed of MnO and MnCr₂O₄ spinel developed on the 9%Mn adding alloy, which providing rather poor protection. The addition of 8%Nb had little effect on the composition of oxide scale and the subsequent sulfidation kinetics.