材料期刊网

Controlled oxidation experiments were performed onKovar alloy by changing oxidation atmosphere, temperature, andexposure time to produce films with different oxide type and　thickness. The results indicated that single Fe3O4 and　single FeO were respectively obtained when Kovar alloy was oxidized　in N2-2.31%H2O-0.95%H2 at 500℃ and in　N2-2.31%H2O-0.5%H2 at 1000℃, and all　kinetic curves followed linear relation; mixed oxides of FeO and　Fe3O4 formed when Kovar was oxidized in　N2-2.31%H2O at 1000℃, and parabolic kineticswere obeyed. Analysis of metallographic cross section of oxidesindicated that oxygen diffusion inward through the oxide scale isresponsible for intergranular oxide, which had formed beneath theoxide scales when the oxide products were mixed oxides of FeO andFe3O4, and which did not occur when the oxide was single　FeO or Fe3O4. The oxidation model was also established.