Oxidation behavior of kovar alloy in N₂/H₂O atmosphere under simulated field condition

The oxidation behavior of kovar alloy (Fe-29Ni-17Co) was studied in N₂/H₂O atmosphere under simulated field condition by weighing method. The weight gain curves of kovar alloy oxidized at 1000℃ in N₂ with different dew points were tested, and the results show that these oxidation kinetics obey parabolic rule. The composition and pattern of the oxides were analyzed by XRD and SEM. Thermodynamical calculations reveal that if kovar alloy is oxidized in N₂/H₂O atmosphere under simulated field condition, external air will infiltrate into the furnace, which increases the partial pressure of oxygen, and the presence of α-Fe₂O₃ in oxides surface is unavoidable. In the condition of a higher dew point and a longer oxidation time, the quantity of α-Fe₂O₃ formed will exceed that of Fe₃O₄.