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- Title
Pack formation and long term oxidation kinetics of TiAl<sub>3</sub> coating on γ-TiAl.
- Authors
Xiang, Z. D.; Rose, S. R.; Datta, P. K.
- Abstract
The aim of this study is to produce microcracking free TiAl3 coatings on γ-TiAl alloy by the pack cementation process and to determine the long-term oxidation kinetics and thermal stability of the coating at high temperatures. It was shown that microcracking free coatings could be prepared in the AlCl3 activated packs containing 4 wt-%Al as the depositing source. The conditions required for the formation of a microcracking free coating are discussed in relation to the pack chemistry at high temperatures. The TiAl3 coatings formed were oxidised in air for more than 6200 h, during which weight gains were measured at regular intervals. The major oxide in the scale was Al2O3. It was observed that a TiAl2 phase zone formed in the subsurface of the scale as a result of preferential oxidation of Al in the TiAl3 coating. It was found that a linear relationship existed between the weight gain and logarithm of time of oxidation at 800°C: Δmt = klln(αt+ 1). The thermal stability of the coating was assessed by measuring the growth kinetics of the TiAl2 interlayer at the boundary between the TiAl3 coating and substrate, which was determined to be d1·4 = 0·1t (d and t in μm and h respectively) at 800°C using the experimental data measured over a diffusion annealing period of more than 6200 h.
- Subjects
TITANIUM alloys; CEMENTATION (Metallurgy); OXIDATION; THERMAL properties; SURFACE coatings
- Publication
Materials Science & Technology, 2005, Vol 21, Issue 10, p1111
- ISSN
0267-0836
- Publication type
Article
- DOI
10.1179/174328405X58931