Masters Theses

Date of Award

5-2016

Degree Type

Thesis

Degree Name

Master of Science

Major

Materials Science and Engineering

Major Professor

Kurt E. Sickafus

Committee Members

Philip D. Rack, Maulik K. Patel

Abstract

The disaster at the Fukushima Daiichi Nuclear Power Plant in March 2011 bought renewed focus to the issue of corrosion in nuclear fuel cladding applications. This thesis reports on the background behind these issues, the investigation strategy, and the analysis of experiments focused on mitigating oxidation of Zr-alloy fuel cladding. This thesis seeks to develop magnetron sputtered Ti-Al-C and Cr-Al-C coatings for Zr-alloy substrates and characterize the as-deposited and corroded samples.

Ti-Al-C and Cr-Al-C coatings were deposited onto ZIRLO, Si, and Al2O3 [Aluminum Oxide] substrates under various sputtering conditions. A combinatorial sputtering method was employed to refine the sputtering parameters. Following each deposition, the coatings were characterized using grazing incidence x-ray diffraction. The crystal structures of the as deposited Ti-Al-C coatings are consistent with TiC [Titanium Carbide] with aluminum substituting onto carbon sites and TiAl3 [Titanium Aluminide]. The as deposited Cr-Al-C coatings were determined to be Cr2AlC [Chromium Aluminum Carbide] MAX phase.

After characterization of the as-deposited coatings, corrosion tests in water were performed on ZIRLO coupons, in a 360 degrees Celsius autoclave. In this thesis, each of the coatings exhibited significant weight gain compared to conventional Zr-alloy claddings. Following corrosion, the samples were analyzed using grazing incidence x-ray diffraction.

Results of corrosion testing show the Ti-Al-C coatings of this study are not fit for the application coatings for nuclear cladding, as multiple oxide and hydroxide phases were produced.

Much of the Cr-Al-C the coating spalled off the substrate during corrosion testing. Cr-Al-C coatings that survived the corrosion testing produced phases consistent with Cr2AlC MAX phase, Al2O3, and Cr2O3 [Chromium Oxide].

In addition to the corrosion study, an in-situ high temperature grazing incidence x-ray diffraction study was performed on the Cr-Al-C on Al2O3 sample. Analysis of the high temperature data suggest the Cr2AlC MAX undergoes a disordered to ordered transformation of the phases Cr and Al sites at increasing temperatures.

Download
Files over 3MB may be slow to open. For best results, right-click and select "save as..."

Share

COinS