Oxidation behavior of Kovar alloy in controlled atmosphere

Controlled oxidation experiments were performed on Kovar alloy by changing oxidation atmosphere, temperature, and exposure 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°C and in N2 −2.31%H2O-0.5%H2 at 1000°C, and all kinetic curves followed linear relation; mixed oxides of FeO and Fe3O4 formed when Kovar was oxidized in N2-2.31%H2 0 at 1000°C, and parabolic kinetics were obeyed. Analysis of metal-lographic cross section of oxides indicated that oxygen diffusion inward through the oxide scale is responsible for intergranular oxide, which had formed beneath the oxide scales when the oxide products were mixed oxides of FeO and Fe3O4, and which did not occur when the oxide was single FeO or Fe3O4. The oxidation model was also established.