محمد امامی

High-temperature erosion-oxidation (E-O) of Ni-20Cr-(0-30)Fe-(0-4)Si was investigated in fluidized bed waste incineration conditions. The specimens were tested in a rig for 250 h, under the collision of hot silica sand contaminated with 0.5 wt.% of NaCl-KCl salt mixture at a temperature of 700 °C. To have a better understanding of the materials’ behavior, the specimens were also oxidized at 560 °C for 100 h in the atmosphere of air + chlorine vapors. The thickness reduction and mass gain of the specimens were used to evaluate the materials under E-O and oxidation conditions, respectively. The specimens were studied using FESEM, EDS, and XRD analysis. At E-O conditions, Ni-20Cr showed the highest material loss (~17.6 mm). The addition of 30 wt.% of Fe to the alloy decreased the wastage to about 6.7 mm. The E-O resistance of Ni-20Cr-30Fe-4Si was about two times lower than the Si-free alloy which indicates that Si had a detrimental effect on the E-O resistance of the alloys. Under oxidation conditions, Ni-20Cr-30Fe showed the highest resistance with a mass gain of about 0.1 mg/cm2. The addition of 4 wt.% Si caused a dramatic decrease in the oxidation resistance of the alloy (mass gain of ~3.8 mg/cm2). The addition of Fe stimulated Cr2O3 scale formation by which the higher E-O and oxidation resistance of the alloy were confirmed. In Ni-20Cr, the formation of a multi-component scale, and in Ni-20Cr-30Fe-4Si, a porous surface scale formed through active oxidation were possibly responsible for the poor performance of these alloys.