Effects of Silicon on High Temperature Oxidation and Erosion-Oxidation Behaviors of Nickel Alloys

The high-temperature erosion-oxidation behavior of a Ni-۲۰Cr-۳Mo-۴Fe alloy containing ۰, ۲, and ۴ wt.% of Si was studied. The specimens were exposed to ۷۰۰ °C silica sand mixed with ۰.۵ wt.% of NaCl-KCl salt for ۲۵۰ h. The difference in the thickness of the samples before and after the erosion-oxidation test was the measure for the material loss. The sample comprising ۴ wt.% of Si showed a thickness reduction of about ۴۵ percent higher than the Si-free specimen. Since the oxide scale is mostly removed by the eroding particles, the specimens were oxidized in the atmospheres of moving air and air+chlorine in a tube furnace at ۵۲۰ °C for ۱۰۰h to better understand the behavior of oxide scales. The Si bearing alloys were interestingly of higher corrosion resistance.  The results of microscopic evaluations were indicative of the effects of Si on the reduction of oxidation rate, deteriorating spalling resistance, and increasing the Cr interdiffusion coefficient in the alloy and a subsequent reduction in the Cr-depleted zone.

کلیدواژه ها:

Ni-۲۰Cr-۳Mo-۴Fe alloy ، Erosion-oxidation ، high-temperature oxidation ، silicon ، آلیاژ Ni-۲۰Cr-۳Mo-۴Fe ، اکسیداسیون فرسایشی ، اکسیداسیون دمابالا ، سیلیسیم