Comparison of the Isothermal Oxidation Behavior of As-Cast Cu–17%Cr and Cu–17%Cr–5%Al Part I: Oxidation Kinetics

Abstract

The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17% Cr-5%Al in air were studied between 773 and 1,173 K under atmospheric pressure. These observations reveal that Cu-17%Cr-5%Al oxidizes at significantly slower rates than Cu-17%Cr. The rate constants for the alloys were determined from generalized analyses of the data without an a priori assumption of the nature of the oxidation kinetics. Detailed analyses of the isothermal thermogravimetric weight change data revealed that Cu-17%Cr exhibited parabolic oxidation kinetics with an activation energy of 165.9 ± 9.5 kJ/mol. In contrast, the oxidation kinetics for the Cu-17% Cr-5%Al alloy exhibited a parabolic oxidation kinetics during the initial stages followed by a quartic relationship in the later stages of oxidation. Alternatively, the oxidation behavior of Cu-17%Cr-5%Al could be better represented by a logarithmic relationship. The parabolic rate constants and activation energy data for the two alloys are compared with literature data to gain insights on the nature of the oxidation mechanisms dominant in these alloys.

On the role of chemisorption in the formation of the target surface compound layer during reactive magnetron sputtering

“…The parabolic constant k shows Arrhenius behavior with an activation energy of 1.1 eV. This value is in line with reported values for other metals such as Fe (1.54 eV [36]) low carbon steel (1.1 eV [37]), Cu/17%Cr alloys (1.72 eV [38]), Ti (2.25 eV [39]), Zr (2.0 eV [39]),…”

Review of high temperature materials

“…At this point, transitions in the exhaust gas yield a cyclical oxidation-reduction procedure with substance ingesting and flagging of tinny pieces, perhaps from start-up and shutdown. There are numerous oxidation investigations on Cu alloys [9][10][11][12]. In one instance, 17% Cr (by weight) was found to reduce growth rates, nonetheless inadequate to form a curative Cr2O3 layer.…”