STRUCTURE OF OXIDE SCALE FORMED ON Cr-Si-Ni ALLOYS

摘要

A double-layered SiO_2/Cr_2O_3 scale formed on alloys would offer excellent high-temperature corrosion resistance. For formation of the double-layered scale Cr-Si-Ni alloys were proposed in the present study. These alloys were prepared by applying a spark plasma sintering method and consisted of CrSi_2 and (Cr, Ni) Si phases. The oxide scales formed on Cr-Si-Ni alloys with various Ni contents at 1273 K were observed and analyzed by using TEM and TEM-EDS. It was found that CrSi_2-(5, 10, 20) mass% Ni alloys form the distinct double-layered SiO_2/Cr_2O_3 scale, and the ratio in thickness of SiO_2 layer to Cr_2O_3 layer depended on the ratio in concentration of CrSi_2 to (Cr, Ni) Si in the substrate. The optimum composition was estimated to be CrSi_2-10mass% Ni and the alloy showed excellent high-temperature corrosion resistance in a fused salt containing sulfur and chlorine.