Fundamental considerations for the development of oxidation-resistant alloys and coatings based on γ-TiAl

Singheiser, L.; Niewolak, L.; Shemet, V.; Quadakkers, Willem J.; Flesch, U.

doi:10.1007/s11661-003-0288-5

Cited by 23 publications

(13 citation statements)

References 19 publications

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“…Effect of Ag and Cr addition on the oxidation behavior of two phase α2-Ti3Al + γ-TiAl in TiAl based alloys have been investigated 34 . These two alloying elements were expected to have reservoir-effect that supports the formation of continuous stable Al2O3 scale as reported previously in single phase TiAl intermetallic compounds 35,36,37 . In this alloy systems, chromium can act as Laves phase-Ti(Cr,Al)2 stabilizer while silver stabilizes Z phase-Ti5Al3O2.…”

Section: Oxidation Of 2-ti3al/ -Tial Alloyssupporting

confidence: 78%

Alloys developed for high temperature applications

Basuki

Prajitno

Muhammad

2017

AIP Conference Proceedings

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Co-based alloys design based on first-principles calculations: Influence of transition metal and rare-earth alloying element on stacking fault energy AIP Conference Proceedings 1805, 060004 (2017) Abstract. Alloys used for high temperatures applications require combinations of mechanical strength, microstructural stability and corrosion/oxidation resistance. Nickel base superalloys have been traditionally the prime materials utilized for hot section components of aircraft turbine engines. Nevertheless, due to their limited melting temperatures, alloys based on intermetallic compounds, such as TiAl base alloys, have emerged as high temperature materials and intensively developed with the main aim to replace nickel based superalloys. For applications in steam power plants operated at lower temperatures, ferritic high temperature alloys still attract high attention, and therefore, development of these alloys is in progress. This paper highlights the important metallurgical parameters of high temperature alloys and describes few efforts in the development of Fe-Ni-Al based alloys containing B2-(Fe,Ni)Al precipitates, oxide dispersion strengthening (ODS) ferritic steels and titanium aluminide based alloys include important protection system of aluminide coatings.

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Section: Oxidation Of 2-ti3al/ -Tial Alloyssupporting

confidence: 78%

Alloys developed for high temperature applications

Basuki

Prajitno

Muhammad

2017

AIP Conference Proceedings

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“…However, an aluminium content of 60-70 at.% is necessary for binary Ti-Al alloys to ensure the formation of a continuous, slowly growing alumina scale in air [12]. Whereas substantial improvement of the oxidation behaviour of c-TiAl was obtained by alloying with further elements, such as Nb, Mo, W, and Hf [10,13,14], surface modifications, in particular alumina forming coatings are considered a more attractive approach to increase the oxidation resistance, independent of compositional adjustments to optimise mechanical properties [15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Oxidation Behaviour of TBC Systems on γ-TiAl Based Alloy Ti–45Al–8Nb

et al. 2009

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The lifetime of thermal barrier coating (TBC) systems on gamma titanium aluminides was determined in the temperature range between 850°C and 950°C under cyclic oxidation conditions in air. Coupons of the alloy Ti-45Al-8Nb (at.%) were coated by pack aluminizing. A subset of samples was subsequently annealed at 910°C for 312 h in argon. During this heat treatment, the two-phase (Nb,Ti)Al 3 plus TiAl 2 microstructure of the coating transformed into single phase c-TiAl. On pre-oxidised aluminized, annealed and bare samples, TBCs of yttria partially stabilized zirconia were deposited using electron-beam physical vapour deposition (EB-PVD). No spallation of the TBCs was observed in cyclic oxidation tests at 850°C for up to 3,000 cycles of 1 h dwell time at high temperature. The two-phase aluminide coating provided effective oxidation protection due to the formation of a continuous alumina scale. The lifetime of this TBC system exceeded 1,400 cycles at 950°C, whereas an aluminized and annealed sample failed after approximately 500 cycles. The TBC on bare substrate failed when thermally cycled at 900°C. In contrast, no spallation occurred with an aluminized and annealed specimen at this temperature during the maximum exposure length of 1,000 cycles, probably related to an increased aluminium concentration in the subsurface region.EB-PVD zirconia top coats were well adherent to the alumina scale and the thermally grown mixed oxides. Failure of the TBC systems observed with bare and annealed samples was associated with spalled oxide scales formed on c-TiAl.

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“…Ag-containing TiAl-based alloys were also reported to reveal improved oxidation behaviour due to the formation of a continuous alumina scale [10]. Considerable efforts have been undertaken to develop coatings providing efficient oxidation protection to increase the service temperature range of g-TiAl alloys [11][12][13][14]. Metallic and ceramic coatings were studied.…”

Section: Introductionmentioning

confidence: 99%

Investigation on the oxidation behaviour of gamma titanium aluminides coated with thermal barrier coatings

Braun

Fröhlich

Ebach-Stahl

et al. 2008

Materials & Corrosion

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In the present study, the applicability of thermal barrier coatings (TBCs) on g-TiAl alloys was investigated. Two alloys with the chemical compositions of Ti-45Al-8Nb-0.2B-0.15C and Ti-45Al-1Cr-6Nb-0.4W-0.2B-0.5C-0.2Si were used. Before TBC deposition, the specimens were pre-oxidised in laboratory air or low partial pressure oxygen atmosphere. Yttria partially stabilised zirconia top coats were then deposited using electron-beam physical vapour deposition (EB-PVD). The oxidation behaviour of the g-TiAl specimens with TBC was studied by cyclic oxidation testing in air at 850 and 900 8C. Post-oxidation analysis of the coating systems was performed using scanning electron microscopy with energy-dispersive X-ray spectroscopy (EDS). No spallation of the TBC was observed for pre-oxidised specimens of both alloys when exposed to air at 850 8C for 1100 cycles of 1 h dwell time at high temperature. SEM micrographs of the thermally grown oxide scale revealed outer mixed TiO 2 /Al 2 O 3 protrusions with a columnar structure. The protrusions contained small particles of zirconia and a low amount of about 0.5 at% zirconium was measured by EDS analysis throughout this outer oxide mixture. The TBCs exhibited excellent adherence on the oxide scale. Intercolumnar gaps and pores in the root area of the TBC were filled with titania and alumina. Below the outer columnar oxide scale, a broad porous zone of predominant titania was observed. The transition region between the oxide scale and substrate consisted of a discontinuous nitride layer intermixed with alumina particles and intermetallic phases rich in niobium formed at the nitride layer/substrate interface. When thermally cycled at 900 8C, the oxide scales on the alloy Ti-45Al-8Nb-0.2B-0.15C pre-oxidised in low partial pressure oxygen spalled off after 540 cycles. For the sample with TBC, spallation was observed after 810 cycles. Failure occurred in the thermally grown oxide near the oxide/nitride layer interface. Microstructural examinations revealed again oxide scales with columnar structure beneath the zirconia top coat and good adherence of the TBC on the thermally grown oxides formed at 900 8C.

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Fundamental considerations for the development of oxidation-resistant alloys and coatings based on γ-TiAl

Cited by 23 publications

References 19 publications

Alloys developed for high temperature applications

Alloys developed for high temperature applications

Oxidation Behaviour of TBC Systems on γ-TiAl Based Alloy Ti–45Al–8Nb

Investigation on the oxidation behaviour of gamma titanium aluminides coated with thermal barrier coatings

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