Jackson, Erika Meier
(2007)
Investigation of Techniques and Procedures to Obtain á-Al2O3 Scales on Coatings with Improved Oxidation Resistance.
Master's Thesis, University of Pittsburgh.
(Unpublished)
Abstract
In this study, two types of coating systems were investigated for their ability to withstand cyclic oxidation conditions. NiCoCrAlY coatings with either 0.1 or 0.5 weight percent yttrium as well as platinum modified aluminide coatings were examined. All of the samples were exposed cyclically, in a bottom-loading furnace at 1100°C in laboratory air. Optical and scanning electron microscopy (SEM) were used to characterize the samples. Various surface treatments were performed on the coatings prior to their exposure. Samples were either exposed as-received, with no treatment, light grit blasted (LGB), light grit blasted and etched with NaOH, or fine polished.The samples containing 0.5 wt.% Y in the as received, LGB and LGB and etched condition, failed by the formation of large oxide protrusions caused by the preferential oxidation of yttrium and by cracking in the coating. The fine polished NiCoCrAlY coatings containing 0.5 wt.%Y did not develop protrusions and did not fail in test. None of the 0.1 wt.%Y coatings with any treatment developed protrusions and none of these failed in test. The PtAl coatings all failed by the formation of large voids at the coating/substrate interface that coalesced and broke through the coating surface, regardless of surface treatment. It was concluded that, in the NiCoCrAlY system, the roughness of the coating surface as well as the amount of yttrium present to oxidize in the coating plays a large role in the coating lifetime. In the PtAl coatings, surface preparation did not appear to have an effect on the coating lifetime. The PtAl coatings and the rough NiCoCrAlY coatings containing 0.5 wt.%Y were found to have similar lifetimes of a few thousand cycles. The polished 0.5 wt.%Y NiCoCrAlY coating and all of the 0.1 wt.%Y coatings exhibited exceptionally long lifetimes, with none of them failing in test.
Share
| Citation/Export: |
|
| Social Networking: |
|
Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
|
| Date: |
25 September 2007 |
| Date Type: |
Completion |
| Defense Date: |
21 May 2007 |
| Approval Date: |
25 September 2007 |
| Submission Date: |
24 May 2007 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Materials Science and Engineering |
| Degree: |
MSMSE - Master of Science in Materials Science and Engineering |
| Thesis Type: |
Master's Thesis |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
corrosion; high temperature oxidation; NiCoCrAlY Coating; Platinum Aluminide Coating |
| Other ID: |
http://etd.library.pitt.edu/ETD/available/etd-05242007-145432/, etd-05242007-145432 |
| Date Deposited: |
10 Nov 2011 19:45 |
| Last Modified: |
15 Nov 2016 13:43 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/7939 |
Metrics
Monthly Views for the past 3 years
Plum Analytics
Actions (login required)
 |
View Item |
![[feed]](/images/feed-icon-32x32.png){kind=icon}