High-Temperature Oxidation Performance of Niobium-Containing Ferritic Stainless Steel for Exhaust Manifold

The high-temperature oxidation behavior of niobium-containing ferritic stainless steel suitable for exhaust manifolds was studied at 1000 °C for up to 50 h. The results showed that for the steels with the stable element Nb addition, the oxidation weight gain per unit area was reduced and the formation of spinel-like oxide MnCr 2 O 4 was promoted. A small amount of niobium tended to segregate at the oxide/metal interface to form the Laves phase, which promoted the formation of the inner oxide layer of SiO 2 and improved the oxidation resistance of the material. When the content of niobium increased to 0.7% (mass fraction), the formation of the SiO 2 oxide layer was inhibited. Adding 0.5% Nb, the weight gain of the sample was 2.33 mg cm −2 and the oxide film thickness was only 8.1 μm, showing the best oxidation resistance.