Oxidation of Iron-Nickel Alloys

Abstract

The oxidation of Fe-Ni alloys in the 500~176 range has been the subject of many investigations. These observations are summarized, and an attempt is made to generalize on the kinetics and mechanism of oxidation. The composition of the oxide film over the entire composition range can be explained in terms of the thermodynamic stability of the oxides of Fe, of NiO, and of Ni,Fe~_zO,. In alloys of all compositions that have been investigated the first reaction is one of selective oxidation, creating a Ni-rich metal layer at the alloy-oxide interface. The growth of a Ni-containing spinel is promoted and formation of FeO is suppressed. This explains the reduction of oxidation rate to about 1000 times less than that of pure iron. The short-time kinetics of oxidation appears to be governed by diffusion through this Ni-rich metal layea" or by diffusion through the Ni-containing spinel. Only at the Ni-rich end of the Fe-Ni system is NiO observed, and this exists next to the alloy interface under a layer of spinel. The reaction between NiO and Fe208 is rapid at these temperatures, thus explaining why these two oxides are not observed together. On prolonged reaction, subscale oxidation and intergranutar attack is observed. Because of the stratification of oxide layers and these secondary effects, the development of a general rate law would be difficult.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14.35 Downloaded on 2015-04-12 to IP

Metastable-Stable Phase Transformation Behavior of Al2O3 Scale Formed on Fe–Ni–Al Alloys

“…Based on the mechanism, we have proposed that Fe 2 O 3 formation promotes a-Al 2 O 3 formation; thus, this critical Fe concentration must also be linked to initial Fe 2 O 3 formation. Foley et al studied oxidation of the binary Ni-Fe alloy system and reported that Fe 2 O 3 was formed on Ni-70 and 59Fe alloys but not on Ni-22Fe alloy at temperatures from 600 to 900°C in air [22]. Although only several data points are available from their study, the critical Fe content to form Fe 2 O 3 obtained in this study broadly agrees with their findings.…”

Effects of Small Additions of Copper and Copper + Nickel on the Oxidation Behavior of Iron

“…If the interface composition had reached point d in Figure 2, the oxidation rate would be controlled by iron diffusion in the c-iron phase, rather than iron ion migration in the oxide. For binary ironnickel alloys, oxidation rates decrease by two to three orders of magnitude compared to pure iron, [26] when diffusion in the solid metal controls the overall oxidation rate. This is significantly larger than the decrease measured here.…”

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

“…Foley reported that the rate constant (K p ) of the Fe-29.6%Ni alloy oxidized at 1000 o C for 0~60 min in an air atmosphere is 3.3×10 -9 g 2 /cm 4 · sec [9]. When compared with the rate constants of the Fe-29.6%Ni alloy with those of the Fe-30%Ni-12.5%Co alloy, the rate constant of the Fe-30%Ni-12.5%Co alloy was higher than that of the Fe-29.6%Ni alloy.…”

“…As a result, a complex oxide of the Fe 3-x Ni x O 4 (0<x 1) type is formed besides Fe 2 O 3 and Fe 3 O 4 , and NiO sometimes appears at the high Ni content region near the interface [7]. However, it has been reported that the results of studies on Fe 3-x [9]. Meanwhile, in the study of the oxidation of the Fe-Ni Invar alloy [4,7,10] it has been performed under the atmosphere of CO/CO 2 , vacuum and air under 1100 o C. The effect of additive elements such as Mn, Cr, Si, Ca, S and P over 1000 o C have been investigated from a standpoint of oxidation and its kinetics of the Fe-Ni based alloy [11].…”