Presentation Title

Early Stage Oxidation of UNS N06230 and UNS N07214 in Dry and Humid Conditions

Faculty Mentor

Vilupanur A. Ravi, Chemical and Materials Engineering, Cal Poly Pomona

Start Date

17-11-2018 2:15 PM

End Date

17-11-2018 2:30 PM

Location

C301

Session

Oral 3

Type of Presentation

Oral Talk

Subject Area

engineering_computer_science

Abstract

Nickel base alloys are widely used in high temperature oxidative atmospheres, such as heat exchangers and land-based gas turbines. To mitigate the deleterious effects of oxidation, chromium and aluminum additions are made to these alloys to form a protective layer chromia or alumina. In dry air, the behavior of chromia- and alumina-forming alloys can be predictable. However, in several instances, high temperature applications contain a significant amount of water vapor, which can lead to adverse effects on the oxidation process. The effects of water vapor are not completely understood and thus, a comparative study was conducted on the oxidation behavior of a chromia- and an alumina-former in dry and wet air. UNS N06230, a chromia-former, and UNS N07214, an alumina former, were oxidized at 1000°C in dry and wet air (15 volume% H2O) for 1 minute, 10 minutes, 1, 5, 10 and 100 hours in a thermogravimetric analyzer (TGA). The oxidized coupons were characterized using X-ray diffraction and scanning electron microscopy. In these early stage oxidation experiments, the UNS N07214 (alumina former) had a lower oxidation rate relative to the UNS N06230 (chromia former). The alumina former showed a more complex behavior in these early stages of oxidation relative to the chromia former.

Summary of research results to be presented

UNS N06230, the chromia former, displayed similar results when oxidized in dry and humid air, with a lower mass gain in wet air at 100 hours of oxidation. X-ray diffraction (XRD) showed that Cr2O3 and MnCr2O4 formed on the surface of the oxide, with MnCr2O4 forming later in the oxidation process. Scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) verified this, showing a chromium and manganese rich oxide on the surface as well as internal oxidation of aluminum. UNS N07214, the alumina former, displayed a more complex behavior in short term conditions. XRD showed that it formed NiO, Cr2O3, NiCr2O4 and Al2O3 on the surface of the alloy. SEM showed similar results with internal oxidation of alumina forming in humid air than in dry air.

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Nov 17th, 2:15 PM Nov 17th, 2:30 PM

Early Stage Oxidation of UNS N06230 and UNS N07214 in Dry and Humid Conditions

C301

Nickel base alloys are widely used in high temperature oxidative atmospheres, such as heat exchangers and land-based gas turbines. To mitigate the deleterious effects of oxidation, chromium and aluminum additions are made to these alloys to form a protective layer chromia or alumina. In dry air, the behavior of chromia- and alumina-forming alloys can be predictable. However, in several instances, high temperature applications contain a significant amount of water vapor, which can lead to adverse effects on the oxidation process. The effects of water vapor are not completely understood and thus, a comparative study was conducted on the oxidation behavior of a chromia- and an alumina-former in dry and wet air. UNS N06230, a chromia-former, and UNS N07214, an alumina former, were oxidized at 1000°C in dry and wet air (15 volume% H2O) for 1 minute, 10 minutes, 1, 5, 10 and 100 hours in a thermogravimetric analyzer (TGA). The oxidized coupons were characterized using X-ray diffraction and scanning electron microscopy. In these early stage oxidation experiments, the UNS N07214 (alumina former) had a lower oxidation rate relative to the UNS N06230 (chromia former). The alumina former showed a more complex behavior in these early stages of oxidation relative to the chromia former.