High-temperature oxidation of silicide-aluminide layer on the TiAl6V4 alloy prepared by liquid-phase siliconizing

Abstract

The method of coating with silicon from the liquid phase (also called the hot-dip method) was presented by several authors who indicated that this was an effective and inexpensive technique capable of producing Ti-Al-Si layers on titanium and titanium-alloy substrates that are rich in ternary phases. The present study examines the effects of the preparation conditions on the structure and properties of the layers. These layers provide excellent protection from high-temperature oxidation, even at a temperature of 950°C. It was proved with SEM and X-ray analyses that the original t2 ternary phase almost completely decomposed into pure Ti5Si4 and TiSi silicides at the temperature of 950°C. The formed layer, consisting of silicide sub-layers, exhibited superior protective properties in high-temperature applications. Keywords: TiAl6V4, silicides, high-temperature oxidation, liquid-phase siliconizing Metodo prekrivanja s silicijem iz teko~e faze (v~asih imenovano hot-dip metoda) je predstavilo ve~avtorjev, ki so potrdili, da je to u~inkovita in poceni tehnika, s katero je mogo~e izdelati Ti-Al-Si plasti na podlagi iz titana in titanovih zlitin, ki vsebujejo ternarne faze. Predstavljena {tudija preiskuje vpliv pogojev priprave na strukturo in lastnosti plasti. Te plasti zagotavljajo odli~no za{~ito pred visokotemperaturno oksidacijo, celo pri temperaturi 950°C. S SEM in z rentgensko analizo je bilo dokazano, da se prvotna ternarna faza t2, pri temperaturi 950°C, skoraj v celoti razgradi v~isti Ti5Si4 in TiSi silicid. Nastala plast, ki jo sestavlja ve~podplasti je pokazala odli~ne za{~itne lastnosti pri visokotemperaturni uporabi. Klju~ne besede: TiAl6V4, silicidi, visokotemperaturna oksidacija, silikoniziranje v teko~i fazi

Microstructures and Isothermal Oxidation of the Alumina Scale Forming Nb1.7Si2.4Ti2.4Al3Hf0.5 and Nb1.3Si2.4Ti2.4Al3.5Hf0.4 Alloys

“…We decided to design alloys (i) with zero volume fraction of Nb ss and (ii) with microstructures that should contain Al rich, Si rich and/or Al and Si rich intermetallic phases, in particular transition metal aluminides and silicides. The choice of intermetallics was guided by the literature [7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24]. Below we discuss why we preferred certain intermetallic compounds to be stable in the microstructures of our alloys.…”

“…It is also known that the alloying of Ti 5 Si 3 with Nb within the solubility limit (about 15.6 at.%) improved the oxidation resistance in flowing dry air at 900 °C of single crystal alloys that were produced using the Czochralski method [23]. Finally, it has been reported that a Ti(Al x Si 1− x ) 2 (0.15 < x < 0.3) coating on Ti–6Al–4V substrate decomposed to a layered structure that consisted of the Ti 5 Si 4 and TiSi silicides at 850 and 950 °C and that the latter significantly improved the oxidation resistance [24].…”

Microstructure and hot corrosion behavior of hot dip siliconized coating on Ni-base superalloy IN738LC

“…Silicon can form a promising protective barrier to withstand the diffusion of oxygen in high-temperature oxidation conditions, through formation of silicides [21]. Therefore, a protective layer, containing SiO 2 , could be formed through the hot dip siliconizing of Ni-based superalloys [22,23]. This inhibits the oxygen diffusion into the surface of base metal [21].…”