Mechanism of niobium effect on corrosion resistance of nickel alloys in commercial helium

Corrosion resistance of Ni-20%Cr alloy samples with 0.1 and 0.9% niobium content in helium at 900 deg C temperature is investigated. It is shown that 0.9% of Nb is enough to protect the alloy against corrosion during 1000 h. Niobium addition facilitates the formation of a dense oxide film strongly bound with the matrix, protecting the alloy against the further oxidation