High Temperature Oxidation and Sulfidation of Ni-15at.%W Coating

Abstract

Ni-15at.%W coatings with film thicknesses of 20-40 ㎛were electroplated on a steel substrate, and their oxidation behavior was investigated at 700 and 800oC in air. For comparison, a pure Ni coating and a bulk Ni were also oxidized. The Ni-15at.%W coating displayed the worst oxidation resistance, due to the formation of less-protective NiO, Fe2O3, NiFe2O4 and NiWO4. The corrosion behavior Ni-15at.%W coatings electroplated on a steel substrate was similarly investigated at 700 and 800oC in the Ar-1%SO2 atmosphere. For comparison, the uncoated steel substrate was also corrosion-tested in the Ar-1%SO2 atmosphere. Severe scale spallation and the internal corrosion of the steel that occurred in the uncoated substrate were not observed in the coated specimen. However, it seemed that the Ni-15at.%W coating cannot be a potential candidate as a sulfidation-resistant coating, due to the formation of less-protective NiO, NiS, WO3 and NiWO4.