| For the improvement of sulfidation resistance, several experimental nickel-base superalloys were newly designed by utilizing computer. The corrosion test was carried out using molten salt of 75%Na₂SO₄+25%NaCl at 900℃. Oxide scales of experimental alloys being examined by EPMA and electron diffraction were shown to consist of Cr₂O₃, TiO₂ at the outer side and Al₂O₃ at the innermost which was tightly adherent to the matrix. It is, therefore, proposed that the superior sulfidation resistance of experimental alloys is attributed to the excellent adherent oxide layers. The relationship between corrosion depth and alloying elements was obtained by means of multiple regression analysis. This led to a conclusion that Ti, Al and Cr improve greatly hot corrosion resistance whereas Co and W influence little it. |
|
