Processing, characterisation and oxidation resistance of βNiAl bond coat: Al and Zr effects
Platinum-modified-βNiAl is a bond coat (BC) material for thermal barrier coatings (TBCs) applications applied on aeroengine hardware to reduce their surface temperatures. However, it is desirable to minimize its production and material costs by the low-cost alternatives of similar performance. It ha...
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University of Belgrade, Technical Faculty, Bor
2021-01-01
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| Series: | Journal of Mining and Metallurgy. Section B: Metallurgy |
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| Online Access: | http://www.doiserbia.nb.rs/img/doi/1450-5339/2021/1450-53392100026C.pdf |
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| author | Chandio A.D. Shaikh A.A. Salman W. Ahmed H. |
| author_facet | Chandio A.D. Shaikh A.A. Salman W. Ahmed H. |
| author_sort | Chandio A.D. |
| collection | DOAJ |
| description | Platinum-modified-βNiAl is a bond coat (BC) material for thermal barrier coatings (TBCs) applications applied on aeroengine hardware to reduce their surface temperatures. However, it is desirable to minimize its production and material costs by the low-cost alternatives of similar performance. It has been acknowledged that the small concentration of the reactive elements (REs), such as Zr, Hf, and Y, could tremendously enhance the oxide adhesion even in some cases better than Pt modified counterparts. The aim of this study was to design and fabricate the Zr-modified-βNiAl bond coat on CMSX-4 superalloy using an aluminizing method. Moreover, the study focused on the development of a systematic understanding of underlying mechanisms behind the beneficial effects of REs. Initially, three sets of BCs were prepared: Zr-free βNiAl (undoped), Al and Zr co-deposited in a single-step process (1SP), and Zr and Al, which were individually deposited in two processing steps (2SP): zirconizing and aluminizing. Such three sets of BCs helped to understand the processing, as well as Zr and Al effects on scale adhesion. In particular, 1SP/2SP BCs showed uniformity of Zr in the form of precipitates and networks that caused hardness enhancement. All BCs were isothermally oxidized at 1150°C for 100 hours wherein 2SP revealed the best spallation resistance, microstructural stability, and its Zr-oxide pegs were extended to substrates. In addition to the Zr effect, BC Al content was found to affect the oxide adhesion equally. Under identical Zr contents (of 1SP and 2SP = 1at %), the higher Al showed the better spallation resistance while lower Al caused the inverse effect of Zr owing to its reactive nature that was termed as over doping. Moreover, it was established that over-doping either local or into entire BC, accelerated the Al depletion that destabilized the βNiAl into γ’-Ni3Al phase. An extensive discussion is presented in the light of the observed results. |
| format | Article |
| id | doaj-art-f66435370f884682ad5e41839f63308b |
| institution | Kabale University |
| issn | 1450-5339 2217-7175 |
| language | English |
| publishDate | 2021-01-01 |
| publisher | University of Belgrade, Technical Faculty, Bor |
| record_format | Article |
| series | Journal of Mining and Metallurgy. Section B: Metallurgy |
| spelling | doaj-art-f66435370f884682ad5e41839f63308b2025-02-02T07:59:23ZengUniversity of Belgrade, Technical Faculty, BorJournal of Mining and Metallurgy. Section B: Metallurgy1450-53392217-71752021-01-0157330130810.2298/JMMB201108026C1450-53392100026CProcessing, characterisation and oxidation resistance of βNiAl bond coat: Al and Zr effectsChandio A.D.0Shaikh A.A.1Salman W.2Ahmed H.3NED University of Engineering and Technology, Metallurgical Engineering Department, PakistanNED University if Engineering and Technology, Faculty of Chemical and Process Engineering, PakistanNorthwestern Polytechnical University, State key Laboratory of Solidification Processing, School of Material Science and Engineering, ChinaNED University of Engineering and Technology, Metallurgical Engineering Department, PakistanPlatinum-modified-βNiAl is a bond coat (BC) material for thermal barrier coatings (TBCs) applications applied on aeroengine hardware to reduce their surface temperatures. However, it is desirable to minimize its production and material costs by the low-cost alternatives of similar performance. It has been acknowledged that the small concentration of the reactive elements (REs), such as Zr, Hf, and Y, could tremendously enhance the oxide adhesion even in some cases better than Pt modified counterparts. The aim of this study was to design and fabricate the Zr-modified-βNiAl bond coat on CMSX-4 superalloy using an aluminizing method. Moreover, the study focused on the development of a systematic understanding of underlying mechanisms behind the beneficial effects of REs. Initially, three sets of BCs were prepared: Zr-free βNiAl (undoped), Al and Zr co-deposited in a single-step process (1SP), and Zr and Al, which were individually deposited in two processing steps (2SP): zirconizing and aluminizing. Such three sets of BCs helped to understand the processing, as well as Zr and Al effects on scale adhesion. In particular, 1SP/2SP BCs showed uniformity of Zr in the form of precipitates and networks that caused hardness enhancement. All BCs were isothermally oxidized at 1150°C for 100 hours wherein 2SP revealed the best spallation resistance, microstructural stability, and its Zr-oxide pegs were extended to substrates. In addition to the Zr effect, BC Al content was found to affect the oxide adhesion equally. Under identical Zr contents (of 1SP and 2SP = 1at %), the higher Al showed the better spallation resistance while lower Al caused the inverse effect of Zr owing to its reactive nature that was termed as over doping. Moreover, it was established that over-doping either local or into entire BC, accelerated the Al depletion that destabilized the βNiAl into γ’-Ni3Al phase. An extensive discussion is presented in the light of the observed results.http://www.doiserbia.nb.rs/img/doi/1450-5339/2021/1450-53392100026C.pdfβnial bond coatoxidation resistancethermal barrier coating (tbc)doping of reactive metals (res)aluminizing |
| spellingShingle | Chandio A.D. Shaikh A.A. Salman W. Ahmed H. Processing, characterisation and oxidation resistance of βNiAl bond coat: Al and Zr effects Journal of Mining and Metallurgy. Section B: Metallurgy βnial bond coat oxidation resistance thermal barrier coating (tbc) doping of reactive metals (res) aluminizing |
| title | Processing, characterisation and oxidation resistance of βNiAl bond coat: Al and Zr effects |
| title_full | Processing, characterisation and oxidation resistance of βNiAl bond coat: Al and Zr effects |
| title_fullStr | Processing, characterisation and oxidation resistance of βNiAl bond coat: Al and Zr effects |
| title_full_unstemmed | Processing, characterisation and oxidation resistance of βNiAl bond coat: Al and Zr effects |
| title_short | Processing, characterisation and oxidation resistance of βNiAl bond coat: Al and Zr effects |
| title_sort | processing characterisation and oxidation resistance of βnial bond coat al and zr effects |
| topic | βnial bond coat oxidation resistance thermal barrier coating (tbc) doping of reactive metals (res) aluminizing |
| url | http://www.doiserbia.nb.rs/img/doi/1450-5339/2021/1450-53392100026C.pdf |
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