Abstract
• Oxidation behaviors of Ni-Fe-Cr alloys with different Cr content were investigated in air at 800 °C and 900 °C °. • A multilayer oxide structure with an inner Cr 2 O 3 , a middle (Ni,Fe,Cr) 3 O 4 , and an outer (Ni,Fe) 3 O 4 /Fe 2 O 3 layers was formed on Ni-Fe-15Cr alloy. • Increasing of oxidation temperature or Cr content for Ni-Fe-Cr alloys not only accelerates to form Cr 2 O 3 inner layer, but also reduces Fe 2 O 3 content. • The (Ni,Fe) 3 O 4 /(Ni,Fe,Cr) 3 O 4 /Cr 2 O 3 layered scale was highly oxidation/corrosion resistant in molten alumina-cryolite at 800 °C. Isothermal oxidation behaviors of Ni–Fe (wt.%) and of the same alloy with additions of 10 and 15%Cr alloys in the air at 800 °C and 900 °C and their anodic behaviors in aluminum electrolysis system at 800 °C were evaluated. The composition morphologies of oxide scales were characterized by XRD, SEM, and EDS. Results show that the scales formed on Ni–Fe alloy at both temperatures consisted of an inner (Ni,Fe) 3 O 4 layer and an outer Fe 2 O 3 layer. For Ni–Fe–10Cr alloy, an external (Ni,Fe) 3 O 4 /Fe 2 O 3 layers and an internal oxidation zone were formed at 800 °C, while a continuous Cr 2 O 3 layer forms at the internal oxidation zone/substrate interface at 900 °C. A multilayer structure oxide of Cr 2 O 3 /(Ni,Fe,Cr) 3 O 4 /(Ni,Fe) 3 O 4 /Fe 2 O 3 was formed on Ni–Fe–15Cr alloy at 800 °C, while at 900 °C the Fe 2 O 3 becomes discontinuous disperses in the (Ni,Fe) 3 O 4 layer close to the surface. Increases in oxidation temperature or Cr content for Ni–Fe–Cr alloys promote the growth of the inner Cr 2 O 3 layer and simultaneously reduce Fe 2 O 3 content. After 4 h of electrolysis at an anode current density of 0.25 A cm −2 , the oxidation resistance of Ni–Fe–15Cr anode is superior to the Ni–Fe anode.
Published Version
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