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Vol.57, No.3, 131 ~ 138, 2019
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| Title |
| Oxidation Behaviors of Alloys Containing β/B2 Phases of Ti-45Al-Mo-Nb Alloys and Evaluation of the Oxidation Behaviors of Si Pack Cementation Coated Alloys |
| 최광수 Kwangsu Choi , 송영범 Youngbuem Song , 이승훈 Seonghoon Yi , 박준식 Joon Sik Park |
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| Abstract |
| Alloys containing the β/B2 phases of Ti-45Al-3Mo, Ti-45Al-3Mo-2Nb and Ti-45Al-5Mo were prepared using an vacuum arc-melting machine. Heat-treatments were carried out at 1250 ℃ in an Ar atmosphere. The temperature of 1250 ℃ is the temperature region of phase α + γ + (β/B2), and the heat treatment condition which improves mechanical properties by decreasing the fraction of the β/B2 phase. The presence of the β/B2 phase can result in relatively weakness at high temperatures and collapses the lamellar structure of the α2 / γ phase during heat treatment. The transient oxidation behaviors of Ti-45Al-(3, 5)Mo-(2Nb) (at%) alloys were investigated in an ambient atmosphere at 900 and 1000 ℃. Initial oxidation behaviors and oxidation resistance of the three alloys were compared at 1000 ℃. The oxidation resistance of the Ti-45Al- 3Mo-2Nb alloy containing Mo and Nb was the most remarkable among the three alloys at 900 ℃ and 1000 ℃. At the same time, Si pack cementation coated Ti-45Al-3Mo-2Nb alloys and oxidation behavior were also analyzed. The phase sequences of the multilayers of τ2 / Ti5Si4 / TiAl3 / TiAl2 /TiAl were observed on the substrate. Also, a diffusion pathway of the silicide coating layers in the ternary phase diagram of Ti-Al-Si was proposed. The oxidation resistance of the silicide coated TiAl alloys was improved during the oxidation tests at 1000 ℃.
(Received December 10, 2018; Accepted January 16, 2019) |
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| Key Words |
| TiAl, oxidation, coatings |
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