Recent progress in the coating protection of gamma titanium-aluminides

Leyens, Christoph; Braun, Reinhold; Fröhlich, Maik; Hovsepian, P.Eh.

doi:10.1007/s11837-006-0062-4

Cited by 72 publications

(43 citation statements)

References 14 publications

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“…The combination of low density, good elevated temperature mechanical strength and excellent creep properties make γ-TiAl alloys attractive alternatives to conventional ferrous alloys for performance automotive components [2,3]. Such potential has already been demonstrated by the use of this material as exhaust values and turbocharger wheels [4,5], however further expansion into this and other markets, such as aerospace, has been somewhat limited by environmental and tribological degradation at elevated temperatures [5].…”

Section: Introductionmentioning

confidence: 99%

High temperature tribological performance of CrAlYN/CrN nanoscale multilayer coatings deposited on γ-TiAl

Walker

Ross

Reinhard

et al. 2009

Wear

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Nanoscale multilayer nitride coatings deposited by advanced PVD techniques have shown particular promise in improving the tribological properties of a number of modal alloy steels [1]. In this study, we report the effect of temperature on the friction and wear behaviour of a CrAlYN/CrN multilayer coating with a CrAlYON/CrON topcoat deposited on γ-TiAl. Deposition was performed by unbalanced magnetron sputtering following a high power impulse magnetron sputtering (HIPIMS) pre-treatment of the polished substrate. A series of pin-on-disc type experiments, sliding against a polycrystalline alumina counterpart, were carried out at four temperatures: 20ºC, 120ºC, 300ºC and 650ºC. An increase in the average steady-state dynamic friction coefficient was observed between the material couple, from 0.56 at room temperature to 0.65 at 120ºC. However at higher test temperatures of 300ºC and 650ºC a decrease in these values was observed to 0.59 and 0.40, respectively. Scanning electron microscopy and energy dispersive X-ray analysis showed evidence of oxidation at the worn surface of all test temperatures investigated, whilst laser confocal microscopy indicated the formation of an interactive tribo-layer above the plane of the original test surface. Focused ion beam sectioning has been used to prepare site specific samples of the tribo-layers for transmission electron microscopy. The evolution of the wear scar composition and structure and its influence on the reduction in dynamic friction coefficient at elevated temperatures is discussed.

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Section: Introductionmentioning

confidence: 99%

High temperature tribological performance of CrAlYN/CrN nanoscale multilayer coatings deposited on γ-TiAl

Walker

Ross

Reinhard

et al. 2009

Wear

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“…Below the alumina scale, the B2-phase containing ~13 at.% oxygen and the Z-phase (Ti 5 Al 3 O 2 ) formed, as confirmed by EDS analysis. In the initial stages of exposure, the Ti-Al-Cr based coatings exhibited a two-phase microstructure consisting of the γ-TiAl, Ti(Cr,Al) 2 Laves or τ phases [4][5][6][7]. Due to rapid Cr diffusion into the substrate and growth of the alumina scale, the coatings depleted in chromium and aluminium with continuing thermal cycling.…”

Section: Resultsmentioning

confidence: 99%

“…The use of protective coatings is a suitable method to improve the oxidation resistance of γ-TiAl components. Intermetallic Ti-Al-Cr coatings were found to form a continuous alumina scale associated with the presence of the Laves phase [4,5]. Their oxidation resistance could be further enhanced by adding small amounts of further alloying elements such as yttrium, hafnium and silicon [6,7].…”

Section: Introductionmentioning

confidence: 99%

“…In combination with internal cooling, the components can operate at substantially higher environment temperatures. Zirconia topcoats were successfully deposited on γ-TiAl alloys and promising lifetimes of the TBC systems were obtained [5,[8][9][10]. Failure observed was related to deterioration in the oxidation resistance of the protective coatings.…”

Section: Introductionmentioning

confidence: 99%

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Intermetallic Ti-Al-Cr Based Layers and Zirconia Topcoats Deposited on Gamma Titanium Aluminides for Environmental Protection

Braun

Fröhlich

Leyens

2011

AMR

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Abstract. Intermetallic Ti-Al-Cr layers with small additions of Si, Zr, W, and Y were deposited on γ-TiAl specimens using magnetron sputtering. The oxidation behaviour of the coated γ-TiAl alloy was studied in the temperature range between 950 and 1000°C under cyclic oxidation conditions in air. Compared to the bare substrate material, the coatings exhibited higher oxidation resistance. During prolonged exposure the intermetallic layers degraded losing their capability to form a protective alumina scale. On coated γ-TiAl samples zirconia topcoats were deposited by electron beam physical vapour deposition. These thermal barrier coating systems exhibited lifetimes exceeding the maximum exposure length of 1000 1 h cycles at 950°C, but failed at 1000°C. Failure was caused by degradation of the bond coats resulting in spallation of the thermally grown oxides.

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“…Deposition of protective and thermally insulating coatings is considered as an effective means to reduce the substrate temperature and suppress both oxidation and oxygen induced embrittlement. Research work in the past decades showed that it was a more effective method by the protective coatings to provide improved oxidation resistance to titanium alloys than by alloying [2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Air plasma sprayed thermal barrier coatings on titanium alloy substrates

Zhou

et al. 2007

Surface and Coatings Technology

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Titanium alloys as lightweight structure materials have been shown more interest in the use at moderately elevated temperatures. However, their poor oxidation resistance at temperature above 600°C limits a wide application. Consequently, thermal protection becomes a concern. 8 wt. % yttria partially stabilized zirconia thermal barrier coatings (TBCs) were air plasma sprayed on titanium alloy substrates (Ti-6.6Al-3.61Mo-1.69Zr-0.28Si in wt.%). The microstructures and mechanical properties of the coating system were studied by using SEM, XRD, MIP, tensile test and Vickers microhardness. The results show that the as-sprayed ceramic coating consists of the non-transformable tetragonal t′ phase of zirconia. The microstructure of the internal substrate keeps unchanged, no reaction and interdiffusion happen obviously at the bond coat/substrate interface during plasma spraying. However, there exists a thin layer of plastic deformation zone in the substrate beneath the bond coat/substrate interface. The surface connected porosity of the as-sprayed ceramic coating shows a typical bimodal pore size distribution. The adhesive strength of the TBCs decreases with increasing the thickness of the as-sprayed ceramic coatings, which is attributed to the residual stresses induced during thermal spraying. The anisotropy in the mechanical properties between the cross section and the top surface of the ceramic coatings is examined.

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Recent progress in the coating protection of gamma titanium-aluminides

Cited by 72 publications

References 14 publications

High temperature tribological performance of CrAlYN/CrN nanoscale multilayer coatings deposited on γ-TiAl

High temperature tribological performance of CrAlYN/CrN nanoscale multilayer coatings deposited on γ-TiAl

Intermetallic Ti-Al-Cr Based Layers and Zirconia Topcoats Deposited on Gamma Titanium Aluminides for Environmental Protection

Air plasma sprayed thermal barrier coatings on titanium alloy substrates

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