High temperature sulphidation of HVOF sprayed CeO 2 modified NiCrAlY coatings in H 2 /H 2 S atmospheres

High temperature sulphidation is one of the most deleterious forms of surface degradation. In the present work, the high temperature sulphidation behaviours of high velocity oxyfuel sprayed NiCrAlY and NiCrAlYCe coatings on high pressure steels in H₂–H₂S mixtures were investigated. Results showed that the NiCrAlYCe coating provided much better sulphidation resistance than the NiCrAlY coating in the given environment. After adding minor CeO₂, the outer layer of scales became compact and showed good adhesion, which decreased the sulphur vapour pressure inside the scale and promoted the formation of more protective inner layer of sulphospinels (Cr, Ni)Al₂S₂.