Kinetics of Fe-30% Ni-12.5% Co invar alloy during high temperature oxidation

Abstract

The oxidation behavior of Fe-30%Ni-12.5%Co Invar alloy possessing low thermal expansion-high strength has been studied by exposing it in temperature ranges of 1000~1200 in an air atmosphere. The formed oxide scale consisted of two layers, an outer layer and an inner layer, and the oxidation mechanism showed uniform growth for all oxidation conditions. The growth rate of the scale had a parabolic relationship with oxidation time, and the estimated activation energy for the growth of the whole oxide layer was approximately 19.84 kcal/mol. The outer scale consisted of five oxide layers, whose outermost scale consisted of major phase CoFe 2 O 4 containing a particulate Fe 2 O 3 phase. The oxide scale of Fe-30%Ni-12.5%Co had different compositions and phases from the Fe-30%Ni alloy investigated in previous studies. Especially, when the alloy was exposed for a longer oxidation time and at a higher temperature, the volume fraction ratio of CoFe 2 O 4 to Fe 2 O 3 was found to increase.

An Investigation into the Nature of the Oxide Layer Formed on Kovar (Fe–29Ni–17Co) Wires Following Oxidation in Air at 700 and 800 °C

“…10. This is in agreement with the existing literature [6,10,18,19]. If the Kovar is to be used in a glass-to-metal seal, then the porosity may allow the molten glass to penetrate the metal leading to increased mechanical keying, improving the bond strength.…”

Layer growth mechanisms on metallic electrodes under anodic polarization in cryolite-alumina melt

“…Cu, Ni, Fe and Co based-alloys appear to be the most promising materials for this application. Many studies have been performed on these alloys, both under polarization in CAM [1][2][3][4][5][6][7][8] and gas-phase oxidation [9][10][11][12][13][14][15][16][17][18][19]. The latter are not directly concerned with inert anode development, but provide interesting information on the corrosion mechanisms of these alloys and their ability to grow protective oxide layers.…”

Microscopic Analysis of the Wetting Morphology and Interfacial Bonding Mechanism of Preoxidised Kovar Alloys with Borosilicate Glass

“…The area near the right side was the Kovar alloy matrix material, where the Fe content further increased. Based on the line scan spectra at the interface, the oxidised Kovar alloy surface had complex layers of oxides [ 24 , 25 ]; thus, the preoxidised Kovar alloy surface was divided into three regions from the outside to the inside (the Fe-rich oxidised layer body region, Fe-poor sparse region, and Kovar alloy matrix). Combined with Figure 4 and from the XRD physical analysis, after the oxidation treatment, the surface generated Fe 3 O 4 and Fe 2 O 3 with two main peaks.…”