EFFECTS OF Ti AND Al ON CORROSION OF Ni-20Cr AND Ni-30Cr ALLOYS IN DRY CO2 GAS

摘要

Model alloys Ni-20Cr and Ni-30Cr with and without 2% Ti and 1.5% Al (wt. %) were exposed to Ar-20CO2 gas at 700 °C. Samples were ground and then electropolished before reaction to avoid cold working effects on alloy diffusion. The undoped Ni-20Cr alloy formed a thick NiO scale and a deep internal oxidation zone containing Cr-rich oxide precipitates. The additions of Ti and Al to Ni-(20, 30)Cr dramatically improved corrosion resistance by promoting chromia formation. All alloys were carburised beneath their scales, forming intergranular Cr-rich carbide precipitates.