Browsing by Subject "stop $TiAl,TiAlNb, TiAlTa$"

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Wpływ modyfikacji składu chemicznego na utlenianie stopów $Ti-Al$
(Data obrony: 2009) Mitoraj, Marzena
Wydział Inżynierii Materiałowej i Ceramiki
Titanium with a wide range of specific properties (e.g. high specific strength, good corrosion resistance, high melting point and biological inertness) is a component of many materials for special applications. Over the last years titanium aluminides were perceived as the most promising structural alloys. Especially interesting are alloys based on two phases $\gamma- TiAl$ and $\alpha_{2}- Ti_{3}Al$ with a lamellar microstructure because of its unusual combination of good mechanical properties and high temperature corrosion resistance. The main objective of this work was to assess the high temperature oxidation resistance of selected Ti-Al alloys with special emphasis on third generation alloys based on two intermetallic phases [$\gamma = \alpha_{2}$] with niobium and tantalum additions ($Ti-46Al-8Nb$ and $Ti-46Al-8Ta$). Moreover the surface of titanium alloys was modified with different coatings. Silicide coatings were deposited by pack cementation on the commercial $Ti-6Al-lMn$ alloy to improve its oxidation resistance at temperatures exceeding $650^{\circ}C$. Thin coatings with several compositions ($Ti-10Si, Ni-20Cr, CrSi_{2}, Cr-5Si, Cr-0.5Si$) were magnetron sputtered onto $Ti-46Al-8Nb$ alloy to inhibit dissolution of gases (oxygen, nitrogen) during the initial stages of oxidation. Oxidation kinetics of uncoated and coated samples as well as morphology and composition of the scales were compared to assess the effectiveness of the applied protection systems. Moreover, oxidation mechanism of $Ti-46Al-8Nb$ alloy at $700^{\circ}C$ and $800^{\circ}C$ was proposed.