DE10358813A1 - Quasi-crystalline alloy used in the production of a component of a gas turbine or compressor comprises a composition containing aluminum, nickel, ruthenium and transition metal - Google Patents

Abstract

Quasi-crystalline alloy comprises a composition: AlwNixRuyMz (where, M = Ir, Pt, Rh, Pd, Cr, V, W, Mo, Nb, Ta, Ti, Hf, Zr, Re, Fe, Co, Y, rare earth, Si or B; and w = 68-75.0 less than x = 25.0 y = 25.0 less than z = 20). An independent claim is also included for a layer structure comprising a substrate, especially a metallic material or super alloy, and a coating made from the above quasi-crystalline alloy.

Description

TECHNICAL TERRITORY

The The present invention relates to quasi-crystalline or as approximant present compounds, a process for their preparation and Uses of such compounds in particular in context with the coating of high temperature exposed components.

Thermal barrier coatings for protecting components exposed to high temperatures and corrosive environments are of enormous importance, for example in the field of gas turbines, in order to increase the service life of such components. Normally, as such thermal barrier coating (TBC) zirconium oxides (ZrO ₂ ) are used, which are stabilized by yttrium oxides (Y ₂ O ₃ ), so-called Y-stabilized zirconium alloys arise (YSZ, yttria stabilized zirconia). The application of such ceramic YSZ layers to a metallic substrate is normally done using methods such as plasma spray (APS, Air Plasma Spray) or electron beam vapor deposition (EB-PVD), cf. for example, Beele W., Marijnissen G., van Lieshout A., (1999), Surf. Coat. Tech., 120-121, 61. The advantage of such coatings is their marked ability to endure high thermal gradients and to isolate the underlying layers of lower melting point base material from the regions of high heat flux and / or high temperature. In order to increase the adhesion between the ceramic layer and the substrate, respectively, in order to ensure protection of the substrate from oxidation, at least one intermediate layer of MCrAlY (where M = Co, Ni or Co / Ni) or other Ni alumininides or a Combination required, as has already been reported several times.

quasicrystalline Materials (QC, quasicrystals) have been through since their discovery Shechtman as metastable, icosahedral quasicrystals with three-dimensional quasiperiodicity studied in a variety of works. Quasicrystals in the narrower sense are phases which have a 5, 10 or 12-fold rotational symmetry, which with the symmetry of the translation lattice of classical Crystal phases are incompatible.

approximants of quasicrystals are translational periodic intermetallic Compounds which diffraction patterns with 5, 8, 10 or 12 times Have pseudo-symmetry. Following the discovery of Shechman a number of publications containing other metastable quasicrystals described, which in tempering in the state of equilibrium corresponding crystalline phase converted. It already became one large number of stable quasicrystalline systems under Al-containing Alloys such as Al-Li-Cu, Al-Fe-Cu, Al-Cu-Ru, Al-Cu-Os, Al-Cu-Co, Al-Ni-Co, Al-Pd-Mn, Al-Pd-Ru, Al-Pd-Os. DC-like However, behavior was also observed in other systems such as Zn-Mg-RE (RE = Y, Gd, Tb, Dy, Er) and Ti (Cr, Mn) -Si-O.

such quasicrystalline compounds as well as some of the corresponding approximants own an unusual one Combination of interesting properties. The best known Property of quasicrystals is not sticky and not to be wettable, what possible technological applications, cf. to Dubois J.-M., (1997), in New Horizons in Quasicrystals, ed. Goldman A.I. et al, World Scientific, 208. Electron transport is also unique in quasicrystals and the approximants (Dubois J.-M., (1997), in New Horizons in Quasicrystals, ed. Goldman A.I. et al, World Scientific, 208).

For the application of quasicrystals or approximants as TBCs exist the most important properties in their mechanical behavior as well the resilience across from Oxidation and corrosion, in thermal expansion and in the thermal conductivity, in the good processability to coatings, as well as in the melting points.

Quasicrystalline compounds of the type mentioned have a high hardness, but have a serious drawback: up to a temperature of a few 100 degrees Celsius, these materials are very fragile. This excessive fragility limits technological applications of quasicrystalline materials (Wollgarten M., Saka H., (1997), New Horizons in Quasicrystals, ed. Goldman AI et al, World Scientific, 320). The problem of fragility could be overcome by using quasi-crystalline alloys as coatings or as constituents of composite materials, for example, B2-phase based alloys (QC + B2). The low fracture toughness under aggressive friction conditions However, this limitation has been overcome by the addition of a relatively ductile phase (Sordelet DJ, Better MF, Logsdon JL, (1998), Mat. Sci. and Engineering, A255, 54).

On the other hand, quasicrystalline compounds are plastically deformable at temperatures T> 0.5T _m (T _m is the melting temperature) and lose their hardness (Dubois J.-M., (1997), in New Horizons in Quasicrystals, ed. Goldman AI et al, World Scientific, 208. An initial experimental proof of the plastic deformability of quasicrystals was obtained for decagonal, quasicrystalline Al ₇₀ Pd ₂₁ Mn _9. Samples of quasicrystalline, icosahedral (i) i-Al-Cu-Fe can be homogeneously grown at high temperature This softening appears to have advantages for the use of quasicrystalline materials as TBCs at elevated temperatures.

In order to increase the stability with respect to corrosion, the composition can be changed. For example, powders of quasicrystalline material and the crystalline β phase around Al ₆₃ Cu ₂₅ Fe ₁₂ exhibit parabolic oxidation at temperatures in the range of 300 to 800 ° C (Sordelet DJ, Gunderman LA, Better MF, Akinc AB, (1997), New Horizons in Quasicrystals, Ed. Goldman AI et al, World Scientific, 296). It was assumed that the quasicrystalline constituents oxidize more slowly than the corresponding crystalline phases. The thermal spray applied i-Al-Cu-Fe phase became the most resistant when chromium was added (Dubois J.-M., (1997), New Horizons at Quasicrystals, ed. Goldman AI et al, World Scientific, 208). Extremely low parabolic oxidation of quasicrystalline Al-Cu-Fe-Cr coatings was confirmed at temperatures in the range of 750-800 ° C (Kong J., Zhou C., Gong S., Xu H., (2003), Surf. Coat., Technol., 165, 281). X-ray photoelectron spectroscopy (XPS) at room temperature showed that dry oxygen oxidizes only the Al in quasicrystals (Jenks CJ, Pinhero PJ, Chang A.-L., Andregg JW, Better MF, Sordelet DJ, Thiel PA, (1997), in New Horizons in Quasicrystals, ed. Goldman AI et al, World Scientific, 157). In the case of Al-Cu-Fe, the oxidation of Cu begins when moist air is added.

The thermal expansion coefficients (CTE) of quasicrystals could be comparable to those of steels or superalloys. For example, the thermal expansion coefficient of an Al ₇₀ Cu ₉ Fe _10.5 Cr _10.5 alloy is approximately 15.6 × 10 ^-6 K ^-1 between 20 ° C and 550 ° C and 18.6 × 10 ^-6 K ^-1 between 550 ° C and 800 ° C (Archambault P., (1997), New Horizons in Quasicrystals, ed. Goldman AI et al, World Scientific, 232).

typical thermal properties of quasicrystals at room temperature are summarized in Table 1, where it can be seen that the thermal properties of quasicrystals close to those insulating metal oxides (Archambault P., (1997), in New Horizons in Quasicrystals, ed. Goldman A.I. et al, World Scientific, 232).

Table 1. Comparison of thermal properties of quasicrystals at room temperature with other materials

The Increase in thermal conductivity of quasicrystals for increasing temperature is high (in contrast to the behavior of ceramic compounds) as a result of the increase in electronic Contribution to the transport properties at temperatures above 300 K.

The coatability as well as industrial applications of quasi-crystalline phases have already been reported several times (see already cited references and others US 5,472,920 . US 5,432,011 . US 5,571,344 . US Pat. No. 5,649,282 . US 5,652,877 . US 5,888,661 . US 6,183,887 . US 6,017,403 , US 5,397,490 . EP 587,186 A1 . US 5,424,127 . US 5,204,191 ). At present, thermal spray processes, in particular plasma spray processes, are mainly used for the production of quasicrystalline coatings. A method of making a quasicrystalline alloy powder has also been described with the aim of processing this powder into a coating using either plasma spray techniques or by using hot isostatic pressing (HIP) techniques to produce monolithic articles to process ( US 5,433,978 ). Said process comprises several steps: (1) in a vessel is placed an overheated, homogeneous composition with respect to the composition, which is the Al-transition metal alloys in superheated form, ie 100-300 ° C above the liquidus temperature of the alloy contains; (2) pouring the melt from the vessel; and (3) gas atomizing the superheated melt using an inert gas at a pressure of about 400 to 1500 psi, resulting in the formation of substantially spherical alloy particles containing a quasicrystalline phase. The above method was illustrated for two alloys: Al ₆₅ Cu ₂₃ Fe ₁₂ and Al ₆₈ Cu ₂₃ Fe ₉ . Methods and parameters of the application of a quasicrystalline coating based on i-Al ₆₃ Cu ₂₅ Fe ₁₂ on Cu and steel substrates were subsequently described in detail. The best results have been reported for the following experimental parameters: (i) plasma syringe - Mach I; (ii) substrate - cold Cu or steel; (iii) starting powder - in atomized form with diameters in the range of 53-63 μm; (iv) tempering parameters - 2h, 700 ° C. The final coating contained the pure i-Al ₆₃ Cu ₂₅ Fe ₁₂ . Sordelet et al. showed that small additions (only in the range of 1 vol.%) of an Fe-Al phase (Fe ₆₈ Al ₃₀ Cr ₂ ) to a quasicrystalline main phase of a composition Al ₆₅ Cu ₂₀ Fe _{15 increase} the friction resistance of the coatings (Sordelet DJ, Besser MF, Logsdon JL, (1998), Mat. Sci. And Engineering, A255, 54).

Another work (Lang CI, Sordelet DJ, Better MF, Shechtman D., Biancaniello FS, Gonzalez EJ, (1998), J. Mater. Res., 15 (9), 1894) describes the preparation of quasi-crystalline coatings of composition Al ₇₀ Pd ₂₀ Mn ₁₀ with plasma spray process and further investigation of the processability and properties of quasi-crystalline Al-Cu-Fe and Al-Cu-Fe-Cr coatings. It was concluded that (i) the thermal diffusivity of quasicrystalline coatings is sensitive to the content of crystalline phases; (ii) the hardness of quasicrystalline coatings does not greatly depend on the phase structure and (iii) the presence of a substantial portion of crystalline phase improves the coefficient of friction of quasi-crystalline coatings.

The preparation of commercial coatings of Al-Cu-Fe-Cr has already been described and low pressure plasma spray processes (LPPS) have also been used to prepare coatings based on Al-Cu-Fe-Cr QC (Kong J., et al. Zhou C., Gong S., Xu H., (2003), Surf Coat, Technol., 165, 281). An interesting method for producing a quasicrystalline coating using a movable wire for thermal deposition has also been described ( US 5,424,127 ). Said wire contains a core of organic or inorganic binder and a quasicrystalline alloy powder or a mixture of powders capable of forming a quasicrystalline alloy, ie a mixture of pure element powders or pre-alloyed powders.

For the quasicrystalline System Al-Cu-Fe was also used for deposition electron beam vapor deposition (EB-PVD, Electron beam physical vapor deposition), and in the case of Ni-quasicrystalline Composites electrodeposition.

The first proposals for the use of quasicrystalline materials have been in the coating of Cu, Al alloys or Cu alloys for cooking equipment, low friction bearings, low wear surfaces and reference surfaces. The materials used in this context contain at least 40% by weight of the icosahedral (i) and / or the decagonal (D) to phase and correspond to the general formula Al _a Cu _b Fe _c X _d I _e , where X is one or more the elements selected from V, Mo, Ti, Zr, Nb, Cr, Mn, Ru, Rh, Ni, Mg, W, Si and the rare earths, I is impurities and e ≤ 2, 14 ≤ b ≤ 30, 7 ≤ c ≤ 20, 0 ≤ d ≤ 10, with c + d ≤ 10.

Thermal barrier layers consisting of a material with at least one highly refractory oxide with low thermal conductivity and at least one quasicrystalline alloy (2-30% by volume) have also been described ( US 5,472,920 ). The proposed quasicrystalline alloys are based on quasi-crystalline Al-Cu-Fe, Al-Cu-Co and Al-Pd-Mn phases, which may be alloyed with other metals or metalloids. The mentioned barriers are deposited by deposition of a mixture of refractory oxide and a quasicrystalline alloy in the vapor phase or in the molten state, or via deposition with the aid of an oxygen-gas flame, which is fed using a movable cord containing the refractory oxide and the quasicrystalline alloy. A family of quasicrystalline alloys is described ( US 5,432,011 ) containing at least 30% by weight of one or more quasicrystalline phases having the following atomic composition: Al _a Cu _b Co _{b '} (B, C) _c M _d N _e I _f , where M is selected from one of the elements Fe, Cr, Mn, Ni, Ru, Os, Mo, V, Mg, Zn, Pd; N is selected from one or more of W, Ti, Zr, Hf, Rh, Nb, Ta, Y, Si, Ge and rare earths; I stands for impurities; a ≥ 50, 0 ≤ b <12, 0 ≤ b '≤ 22, 0 <b + b' ≤ 30, 0 ≤ c ≤ 5, 8 ≤ d ≤ 30, 0 ≤ e ≤ 4, f ≤ 2. The above Alloys may be classified into different groups having one or more of the following properties which make them suitable for coating: (i) high hardness; (ii) low but not negligible deformability; (iii) heat stability; (iii) increased corrosion resistance due to low or nonexistent Cu contents; (iv) thermal conductivity comparable to that of YSZ (Table 1) remaining below 12 W / m K up to a temperature of 900 ° C (below that of stainless steel); (v) CTE depends only very slightly on the temperature and is about 9.0 × 10 ^-6 K ^-1 (close to that of stainless steel); (vi) Superplasticity above 600 ° C. Other documents ( US 5,652,877 ) also describe methods of making surfaces which are particularly resistant to wear, friction, cavitation, erosion, corrosion, high temperature or oxidation. In this case, a layer of a quasi-crystalline alloy is applied to the surface of a metallic substrate. The quasicrystalline alloys essentially correspond to those of US 5,432,011 but the suggested range for the variable b, which describes the Cu content, is 0 ≤ b ≤ 14. The in the two documents US 5,432,011 and US 5,652,877 The materials described are proposed for use as separate thermal barriers below 700 ° C, as adhesion promoting sub-layers for a layer which serves as a thermal barrier, and which consists of a thermally protective material (such as YSZ) above 600 ° C ,

Heat protection systems containing quasicrystalline materials are in US 5,571,344 . US Pat. No. 5,649,282 . US 5,888,661 , and US 6,183,887 described. The document US Pat. No. 5,649,282 describes a composite structure containing substrate and a heat protection element on this substrate, wherein the heat protection element consists essentially of a quasicrystalline alloy. The thermal diffusivity of the quasicrystalline alloy is lower than 2.5 × 10 ^-6 m ² / s at room temperature and does not increase more than a factor of 3 for temperatures up to a range of 650-750 ° C. The quasicrystalline alloy consists of Al _a Cu _b Fe _c X _d J _e I _g , wherein X is selected from B, C, P, S, Ge; J is at least one of the metals V, Mo, Ti, Zr, Nb, Cr, Mn, Ru, Rh, Ni, Mg, W, Hf, Ta and the rare earths; I stands for impurities; and wherein 0≤g≤2, 14≤b≤30, 7≤c≤20, 1≤d≤5,21≤b + c + e≤45. The patents US 5,571,344 . US 5,888,661 , and US 6,183,887 treat different connections. In US 5,888,661 describes a quasicrystalline alloy of the general formula Al _a Pd _b Mn _c X _d E _e T _f G _g , wherein X is at least one of the elements selected from B, C, Si, Ge, P, S; E is at least one of Fe, Mn, V, Ni, Cr, Zr, Hf, Mo, W, Nb, Ti, Rh, Ru, Re, Ta; T is at least a rare earth; G stands for impurities; and wherein 15 ≤ b ≤ 25; 6 ≤ c ≤ 16; 21 ≤ b + c + e ≤ 45; 0 ≤ f ≤ 4; 0 ≤ g ≤ 2; 0 ≤ d ≤ 5. The document US 5,571,344 describes the following alloy: Al _a X _d J _e I _g , where X is at least one of the elements selected from the following group: B, C, Si, Ge, P, S; J represents at least one of V, Mo, Cr, Mn, Fe, Co, Ni, Ru, Rh, Pd; I stands for impurities; and wherein 0 ≦ g ≦ 2, 0 ≦ d ≦ 5, 18 ≦ e ≦ 29. Finally, a heat-resistant element according to FIG US 6,183,887 a quasicrystalline alloy which has the following general formula: Al _a Cu _b Co _c X _d Y _e T _f I _g , where X is at least one metalloid selected from B, C, Si, Ge, P, S; Y denotes at least one metal selected from the group Fe, Mn, V, Ni, Cr, Zr, Hf, Mo, W, Nb, Ti, Rh, Ru, Re; T is at least one element of the rare earths; I stands for impurities, and where 14 ≤ b ≤ 27; 8 ≤ c ≤ 24; 28 ≤ b + c + e ≤ 45; 0 ≤ f ≤ 4; 0 ≤ d ≤ 5; 0 ≤ g ≤ 2 and e> 0.

In addition, rapid quenching has been proposed for the production of Al-based quasicrystalline alloys of the type Al _x L _y M _z , which have high strength and rigidity without any oxides, where [L = Mn or Cr, M = Ni, Co or Cu (at least one of them); x + y + z = 100, 75 ≦ x ≦ 95, 2 ≦ y ≦ 15, 0.5 ≦ z ≦ 4] ( US 6,017,403 ). Magnetic quasi-crystalline material consisting essentially of an Al-based phase is used in the US 5,397,490 disclosed. Excellent hard and heat resistant composites are reported to be 20 vol. % or less of an Al-based quasicrystalline alloy homogeneously dispersed in a matrix consisting of Al and a solid solution of Al ( EP 587186 ). The latter alloy has a composition according to the general formula AlNi _a X _b or AlNi _a X _b M _c wherein X is one or both of the elements Fe and Co; M at least one of the elements Cr, Mn, Nb, Mo, Ta, W; and where 5 ≤ a ≤ 10; 0.5 ≤ b ≤ 10; 0.1 ≤ c ≤ 5.

The major drawback of the prior art quasicrystalline structures for their use as coatings in the high temperature region is usually their insufficiently high melting point. The Most known quasicrystalline phases melt below 100 0 ° C (for example, the solidus temperature of Al ₇₃ Ni ₁₄ Co ₁₃ at 940 ° C, Al ₇₀ Pd ₂₁ Mn ₃ melts at 860 ° C, Al ₆₂ Cu ₂₀ Co ₁₅ Si ₃ at 920 ° C (Wolf B., Bambauer K.-O., Paufler P., (2001), Mat. Sci. and Engineering, A298, 284), Al _63.5 Cu ₂₄ Fe _12.5 at 950 ° C (Dubois J. -M., Archambault P., Colleret B., (1996), US 5,571,344 ). The decagonal quasicrystalline Al-Ni-Co phase in the narrow composition range of ≈ 71.5 at.% Al and ≈ 5 at.% Ni has a slightly higher melting point in the range 1100-1150 ° C.

PRESENTATION THE INVENTION

Of the The invention is therefore based on the object, a new quasicrystalline or as a approximated compound available put. The compound should have advantageous properties, as specifically related to use as a coating of hot gases flowing around Components which are used, for example, in gas turbines, required are. This is how the connection and the class should be of compounds have a corresponding strength and density, should have a low thermal conductivity, a high stability in terms of oxidation, and behavior in relation to the thermal expansion should be similar be like those typical substrates, such as substrates made of superalloys.

The solution to this problem is achieved in that the compound has a nominal composition of the following type: Al _w Ni _x Ru _y M _z

Having, where M is at least one of the elements selected from the group: Ir, Pt, Rh, Pd, Cr, V, W, Mo, Nb, Ta, Ti, Hf, Zr, Re, Fe, Co, Y, rare Earth, Si, B is. In addition, w = 68-75, 0 <x ≤ 25, 0 <y ≦ 25, 0 <z ≦ 20, and at least 30% by mass of the compound is a quasicrystalline structure or as a approximant.

Of the The core of the invention thus consists in the surprising finding that the addition of top-melting Metals to a decagonal phase of the type Al-Ni-Ru to an alloy with much higher Melting point and the aforementioned advantageous properties. Preferably the proportion of Al is set in the following range: w = 71 - 74. Further preferably, the content of Ni in the following range set: x = 10 - 20. Further, preferably, the proportion of Ru in the following range set: y = 7 - 15. The content of M is preferably set in a range of 1 <z ≦ 10.

Farther preferred settings of the parameters are as follows: if M = Co, then z ≤ 15; if M = Fe, then z ≤ 10; if M is selected is from the group: Ir, Pt, Rh, Pd or a mixture thereof, then z ≤ 15, preferably z ≤ 10; if M selected is from the group Cr, V, W, Mo, Nb, Ta, Ti, Hf, Zr, Re, or one Mixture thereof, then z ≤ 5, preferably z ≤ 2; if M is selected is from the group Y, Si, B or a mixture thereof, then z ≤ 3, preferably z ≤ 1.

With regard to the melting point, particularly good results are obtained when a nominal composition has one of the following formulas: Al ₇₂ Ni ₁₁ Ru ₁₂ Ir ₅ ; Al ₇₄ Ni ₁₁ Ru ₁₀ Ir ₅ , or a mixture thereof is used.

In principle, it is possible that multinear phases continue to be present in small constituents, in particular based on intermetallic compounds. Such intermetallic compounds may be approximants of the decagonal phase, in particular of the type Al ₁₃ Ru ₁₄ and / or Al ₂ Ni ₃ .

A preferred use of such a compound or a Combination of such compounds is to shape them a coating applied to a substrate. This layer can be applied either as a single layer, or in one Multi-layer construction, wherein the compound in multiple layers or alternatively only in the outermost Layer can be present.

A further preferred embodiment of the present invention accordingly relates to a layer structure which is characterized in that on a substrate, in particular a metallic material or a superalloy, a quasicrystalline coating, as described above, is applied in particular as a surface coating.

at Such a multi-layer structure should advantageously between at least one of the substrate and the quasicrystalline coating as a diffusion barrier (in particular for Al, but also for other constituents), acting intermediate layer may be arranged. In this context turns out that for this specific type of surface coating interlayers from a pure supreme melting Metal such as particularly preferred Ru, Ir, Re, Pt, etc. advantageous can be used. Alternatively or in addition Is it possible, the at least one intermediate layer as a layer of a solid solution a melting pot Metal, such as in particular preferably Ru, Ir, Re etc., with B2-structure-based intermetallic Compounds containing 26-60 Atom% Al to design, with such an intermediate layer preferred has a melting temperature which is at least 400 ° C above the operating temperature of the coating is (i.e., 400 ° C above the temperature of this surface flowing around Gases when used for example in gas turbines).

Farther The present invention relates to a process for the preparation a coating, as described above, respectively one said layer structure. The process is characterized thereby from that the inventive Compound using thermal spray techniques such as APS, Electroplating, or vapor deposition such as EB-PVD, or optionally a combination of these methods, or other galvanic methods is applied. The properties of the final layer can be improved be followed by the individual layer or the layer structure subsequently is tempered. Preference is given to tempering before spraying or the pulverization takes place.

Not Finally, the present invention also relates to a use such a compound, preferably as a coating or layer structure, as a material for a component which is exposed to high temperatures, and which especially hot gases is exposed respectively from hot Gases flow around becomes. This may be a component of a gas turbine or a Compressor act, particularly preferably a blade or guide vane of a gas turbine or a compressor.

Preferably the compound is particularly preferred as the coating used directly exposed to the hot gases surface, where appropriate below the coating another functional layer in particular for adhesion or barrier action, in particular as a diffusion barrier, is present. Especially when used as a coating for gas turbine applications it proves to be advantageous, the coating has a thickness of in the range of 10-400 microns, in particular preferably in the range from 100 to 200 μm.

Further preferred compounds, coatings, methods and uses are in the dependent claims described.

SHORT EXPLANATION THE FIGURES

The Invention is intended below with reference to embodiments in connection closer with the drawings explained become. Show it:

1 Influence of iridium addition on properties of the decagonal phase of Al-Ni-Ru, where a) X-ray diffraction pattern of decagonal Al-Ni-Ru and Al-Ni-Ru-Ir phases, b) curves of differential thermal analysis (DTA) of decagonal Al Ni-Ru and Al-Ni-Ru-Ir phases; c) Differential thermal analysis (DTA) curves of prior art Al-Ni-Co dekagonal phases;

2 Application of decagonal Al-Ni-Ru phases as thermal and corrosion-resistant coatings for gas turbines, wherein the diffusion barrier is preferably thermodynamically and / or kinetically compatible with the superalloy layer SX and the quasi-crystalline surface coating;

3 Estimating the annealing times: Formation of pure decagonal phases during annealing at 950 ° C of the alloy 2 im with the composition Al ₇₃ Ni ₁₆ Ru ₁₁ ;

4 Increase in weight during the oxidation of a quasicrystalline alloy of Al-Ni-Ru under laboratory air at 950 ° C and 1050 ° C, respectively;

5 Thermal conductivity k of Al-Ni-Ru-Ir alloy 5;

6 X-ray diffraction pattern of simple decagonal coatings using VPS, APS and high-velocity oxy-fuel (HVOF) methods compared with the corresponding alloy 2 cast respectively annealed;

7 Images of Alloy 2: a) SEM image using VPS, b) APS, c) HVOF, d) metallography uptake using VPS, e) APS, f) HVOF.

WAYS TO PERFORM THE INVENTION

The thermal stress as well as the oxidation of blades or vanes in gas turbines under the influence of high temperatures in combination with the oxidative or corrosive conditions reduces the possible life and the maximum possible interpretation of the temperature of the combustion process, which on the one hand the efficiency of the turbine reduced and on the other hand the maintenance costs increased. According to the prior art, materials such as yttria-stabilized zirconia (Yttria stabilized ZrO ₂ , abbreviated YSZ) are known in connection with the coating of such loaded components. Such coatings are referred to as ceramic thermal barrier coatings. Despite their inadequate mechanical stability and integrity, despite the high specific gravity, and although such layers are substantially permeable to oxygen, these materials are still unique in protecting the surfaces of the base metal, particularly the first stage buckets and vanes of low pressure gas turbines , There are known to be the particularly high temperatures in the range of 900 to 950 degrees Celsius. The uncooled third and fourth stages can be made with the aid of titanium alloys which have a good strength to density ratio but require protection against oxidation or corrosion.

Problematic Among these compounds is, inter alia, that the thermal expansion the metallic and the ceramic parts are different, that mixtures of different oxides (among others spinels) especially at the interface between the YSZ and the underlying layer. Moreover can be harmful Interdiffusion take place.

The proposed compounds which are suitable for the coating of such Components are based on quasicrystalline (QC, quasicrystalline) Compounds of the type Al-Ni-Ru-M (where M is at least one of the elements selected from the group of precious metals such as Ir, Pt, Rh, Pd, transition metals such as Cr, V, W, Mo, Nb, Ta, Ti, Hf, Zr, Re, Fe, Co, Y, as well as rare earths, and Si, B). Quasicrystals are non-periodic intermetallic phases with decagonal (D-phase) or icosahedral (i-phase) symmetry. Approximants of Quasicrystals are true intermetallic compounds with structures, similar to those of quasicrystals are.

In this context shows 1 the influence of metal addition (iridium addition in the present case) on the properties of the decagonal phase of Al-Ni-Ru. In this case, a) shows an X-ray diffractogram of decagonal Al-Ni-Ru (top) and Al-Ni-Ru-Ir (bottom) phases. It can be seen that the structure does not change significantly despite the addition. From the curves of differential thermal analysis (DTA) of decagonal Al-Ni-Ru and Al-Ni-Ru-Ir phases according to 1b) the increase of the melting temperature can be detected by adding M The obtained value of 1170 ° C for the decagonal Al-Ni-Ru-Ir phase could be further increased by adding other elements. As comparison can be found in 1c) Differential Thermal Analysis (DTA) curves of prior art Al-Ni-Co dekagonal phases.

The basic composition of the present decagonal phase is Al ₇₃ Ni ₁₆ Ru ₁₁ . The Al content in such coatings can vary in the range of 68 at% to 75 at%. The additional element M can be present in a content of up to 10 atom% (or 20 atom% for M = cobalt), wherein Ni and / or Ru can be replaced by M. In addition, the proposed quasicrystalline compounds, or coatings thereof or starting material therefor, may contain minor proportions of multinary phases based on intermetallic compounds, which may be considered as approximating the decagonal phase. For example, Al ₁₃ Ru ₄ and / or Al ₃ Ni ₂ are suitable. In the present specification, both the pure decagonal phases of the type Al-Ni-Ru-M and their relevant approximants are referred to as quasi-crystals or quasicrystalline phases.

Of course, in this compounds impurities from other elements in low Shares occur as in the normal processing of the alloys can hardly be avoided.

Moreover It must be noted that other elements which are the most advantageous Do not affect the properties of the proposed compounds, may also be present in the alloy without thereby brought out of the invention would.

Preferably is used as starting material for the deposition of a coating a pure decagonal Al-Ni-Ru-M Phase uses which over a corresponding tempering of a cast alloy of the associated composition can be obtained.

• (1) niedrige Wärmeleitfähigkeit, wie sie für Quasikristalle charakteristisch ist,
• (2) schützendes parabolisches Oxidationsverhalten,
• (3) vergleichsweise hohe Schmelzpunkte verglichen mit anderen Al-enthaltenden Quasikristallen,
• (4) Wärmeausdehnungskoeffizienten, welche mit jenen von Superlegierungen respektive Substraten von Superlegierungen vergleichbar sind,
• (5) erhöhte Dichte welche die Abscheidung von dichteren Beschichtungen durch thermische Sprayverfahren erlaubt.

The proposed decagonal Al-Ni-Ru-M alloys and their approximants have a variety of useful properties, such as:

• (1) low thermal conductivity characteristic of quasicrystals
• (2) protective parabolic oxidation behavior,
• (3) comparatively high melting points compared to other Al-containing quasicrystals,
• (4) coefficients of thermal expansion comparable to those of superalloys and superalloy substrates, respectively;
• (5) increased density which allows the deposition of denser coatings by thermal spray methods.

Become Such compounds as coatings, for example, of components used which exposed to high temperatures as well as corrosive environment are, so can both a substantial increase the efficiency and the lifetime as well as a reduction of the maintenance costs for such components be achieved. A coating of the proposed material can be made by a thermal spray method. alternative Is it possible, special so-called "extended electroplating "methods, if necessary in several stages.

Preferably is below the layer of the proposed quasicrystalline Material an intermediate layer.

In connection with such intermediate layers, it must be mentioned that such diffusion barriers are also already known in coatings according to the prior art. A large difference in non-equilibrium composition (particularly in terms of Al content) between a quasicrystalline coating and the underlying substrate can lead to problems with interdiffusion. An extension of the lifetime of a quasicrystalline coating can be achieved accordingly by introducing a diffusion barrier between the substrate and the surface coating. For example, Sanchez A., Garcia de Blas FJ, Algaba JM, Alvarez J., Valles P., Garcia-Poggio MC, Aguero A., (1999), in Quasicrystals, ed. By Dubois J.-M. et al, 447 on a mixture of a quasicrystalline phase of the type Al ₇₁ Co ₁₃ Fe ₈ Cr ₈ with Y ₂ O ₃ or with NiAl + Y ₂ O ₃ .

A disadvantage of such intermediate layers is the fact that such ceramic layers reduce the mechanical stability of the entire multi-layer structure. In connection with such diffusion barriers, mention must be made of such barriers for superalloys coated with MCrAlY (X), PtAl and NiAl US 6,306,524 : Ru-based solid solutions; RuX phases (X = Al, Zr or Hf); Ni ₃ Al alloyed with Ta, W, B; M ₃ X intermetallic compounds (M = Ni, Co or Pt; X = Ta or Nb); high melting intermetallic compounds such as Cr ₂ Ta or Ni ₄ W; Re-rich alloys with a structure alloyed with Al, Pt or Cr. Ir- or Ta-modified aluminized coatings are efficient diffusion barriers for conventional Al coatings on superalloys, as described in Wu F., Murakami H., Suzuki A., (2003) Surf. Coat. Tech., 168, 62 is reported.

In the present case, such an intermediate layer of a pure refractory metal (so-called refractory metal) such as Ru, Ir, Re, etc., or a combination thereof is produced. Also possible are solid solutions based on such metals with B2 structure-based intermetallic compounds containing 26 atom% to 60 atom% Al. The B2 structure-based intermetallic compounds have high melting points, which ensure low diffusion rates of the species within the alloy. In some cases, there is also an equilibrium to both adjacent layers. As an example, come B2 Al-Ni-Ru-M phases in question. In addition, such B2 phases could, with appropriate compositions, have an additional protective effect, as would be the case for example in the DE 103 32 420.8 is described. In any case, such an intermediate layer acts as a diffusion barrier between the substrate of superalloys (low Al content) and the surface layer of the decagonal phase (high Al content).

The thermodynamic solution In this case, it consists of phases from the relevant phase diagram which is in equilibrium with the γ + γ 'phases of the substrate and the decagonal phase of the surface coating stands. Preferably is there a balance between both Interfaces. Kinetically, interdiffusion can be achieved by using a high melting point Delayed metal or an alloy based thereon due to the low mobility species at operating temperatures. Preferably prevented such an alloy for an interlayer diffusion both kinetically and thermodynamically.

It must be generally noted that the use described the proposed quasicrystalline compounds as thermal Barrier for Gas turbines are used for illustration, and not as a limitation shall be. The proposed compounds can be used quite generally as protective layers in terms of heat or corrosion, e.g. in appropriate industrial applications as well as household applications. In question, for example also turbochargers, jet engines, stoves and the like.

A possible layer structure is in 2 shown. The Al-Ni-Ru-M phases act as thermal and corrosion-resistant coatings for, for example, gas turbines, wherein the diffusion barrier is preferably thermodynamically and / or kinetically compatible with the superalloy layer SX and the quasi-crystalline surface coating.

Of the proposed multilayer structure can with the help of different Process are produced. Both the quasicrystalline coating as well as the diffusion barrier can be made using spray methods or followed by electroplating be prepared by aluminising. In the latter case should the quasicrystalline layer on the surface of pre-deposited Diffusion barrier are applied, which has a mean Al Proportion in comparison with the quasicrystalline layer and the substrate made of superalloys.

Of the proposed layer structure of 2 layers can instead of a classical construction of YSZ and a connecting layer (BC, bond coat), both functions (bond coat and TBC, thermal barrier coating) become. Such coatings without ceramic layers have a much bigger Resistance to mechanical cracks than the prior art coatings. Alternatively you can the proposed quasicrystalline alloys also with others ceramic diffusion barriers are used. It is also possible that to use proposed compounds without a diffusion barrier, but then it is recommended, the corresponding component only lower temperatures suspend, so that the contribution of interdiffusion is not material becomes. Under special conditions, such a quasicrystalline Alloy also coated with a ceramic 5 insulation layer become a higher one or to ensure graduated thermal protection effect for the base material.

The preparation of a coating is described below, starting with a coating of Al ₇₃ Ni ₁₆ Ru ₁₁ is used. In addition, an intermediate layer with a B2-based Al-Ni-Ru structure based on Al ₅₀ Ni ₄₀ Ru _{10 is} given.

The quasi-crystalline compounds of the type Al-Ni-Ru-M and those of the prior art (Al-Co-Ni) were prepared in an arc with a non-consumable tungsten electrode under an argon atmosphere with a titanium oxygen getter on a water-cooled copper hearth. The cast alloys were annealed under 15 argon at 900 ° C for one week. The original compositions, the tempering regimes, and the results of the characterization are shown in Table 2 and in FIG 3 summarized. Table 2: Characterization of Al-Ni-Ru-M alloys annealed under Ar at 900 ° C for one week ^*

As from Table 3, could be particularly satisfactory compacted decagonal alloys without mechanical cracks Use of the HIP method (hot isostatic pressure).

Table 3: Parameters of HIP *

Separate Although pores of Example 1 in Table 3 can be ground by HIP be reduced, but certain mechanical defects remain. Corresponding were the decagonal samples for the physical measurements using the in Table 3 below No. 2 (CIP, cold isostatic pressure).

The Alloys were measured using powder X-ray diffraction (Scintag X-ray powder diffractometer with a Ge detector using Cu radiation). Scanning electron microscopy (SEM) was used in back-scattering mode at 10 kV accelerating voltage on a Hitachi S-900 "in-lens" field emission scanning electron microscope using a standard Everhard-Thornley SE detector and of a YAG type BSE detector. Energy dispersive X-ray spectroscopy (energy dispersive X-ray spectroscopy, EDS) was at 15-30 kV certification voltage on a "LEO 1530" device under Using the software VOYAGER performed. Microprobe analysis (Electron microprobe analysis, EPMA) was performed on a "CAMECA SX50" microanalyzer.

Corresponding could the composition of the decagonal Al-Ni-Ru-M phases and whose approximants are uniquely determined.

The phase transition temperatures were measured using differential thermal analysis (DTA) on a Perkin Elmer DTA 7 instrument up to a temperature of 1500 ° C in Al ₂ O ₃ crucibles under high purity argon at heating rates, respectively, cooling rates of 10 ° C / min. The data obtained are summarized in Table 2.

The melting points of the decagonal phases of Al-Ni-Ru of about 1070 ° C are increased by the addition of iridium (see. 1 ). This means that the increase in solidus temperature of the decagonal phase is approximately 20 ° C / (1 at.% Ir). The synthesized quaternary decagonal Al-Ni-Ru-Ir phase has a solidus temperature of about 1170 ° C. The addition of Ni to Al ₁₃ Ru ₄ instead of Ru reduces the melting point of this approximant.

Oxidation tests were performed under air at 950 ° C and 1050 ° C. The isothermal kinetic measurements show parabolic oxidation at both temperatures, cf. to 4 , The only product of the interaction between oxygen and the alloys is the formation of pure α-Al ₂ O ₃ , which forms a continuous layer on the metallic substrate. These protective deposits are (i) monophasic, (ii) dense, (iii) contain no significant portion of Ni and Ru, and (iv) have good adhesion to the layer.

It can no remarkable differences in the oxidation mechanism of QC Al-Ni-Ru-M alloys are observed at 950 and 1050 ° C.

The laser flash method was used to measure thermal diffusivity in a "TC-3000H / L SINKU-RIKO" instrument, measuring 10 mm diameter samples with a thickness of 1 mm. The decagonal Al-Ni-Ru-M alloys have a low thermal conductivity, which is typical for quasicrystals (cf 5 ).

The Measurement of thermal expansion coefficients (coefficients of thermal expansion, CTE) were measured on a DIL 402C (push-rod) dilatometer performed, which is manufactured by the company NETZSCH (Germany). The Samples became rods cut to a diameter of 5 mm and a length of 5 mm. The device was operated in a temperature range of 20-1000 ° C, the temperature with a speed of 5 ° C / min changed has been. The reproducibility was verified by adding each sample 3 times was measured. The measurements were carried out under argon atmosphere to To avoid oxidation. The measured coefficients were close with those as for the Ni-based superalloy substrates are typical.

The starting alloy 2 (Al ₇₃ Ni ₁₆ Ru ₁₁ ) was melted for coating in a 75 kW and 2000 Hz vacuum induction melting furnace under 140 mbar partial pressure of high purity 8.4 Ar in a MgO crucible at a temperature of approximately 1500 ° C. After reflowing, the alloy rod was annealed at 950 ° C for 160 hours to form a pure decagonal phase.

The pulverization was carried out using a countercurrent milling method with a 100 AFG instrument (HOSOKAWA ALPINE AG & Co. OHG, Germany) under a nitrogen atmosphere. The target parameters were d ₅₀ = 30 μm, d ₁₀₀ = 63 μm, the Malvern method was used for the measurement of the particle size distribution.

The coatings were applied to the substrates using methods such as VPS, APS and HVOF, the substrates being Advanced CMSX-4 Ni based superalloys. The thickness of the layers varied between 100 nm to 400 μm. A sandwich two-layer VPS structure (Al-Ni-Ru D phases) + (Al-Ni-Ru B2 structure-based alloy of a composition Al ₅₀ Ni ₄₀ Ru ₁₀ ) was also constructed. The corresponding measurements are in the 6 as well as recordings in 7 shown. The porosity of the coatings was determined using the AnalySis software package (Soft Imaging System GmbH, Germany) using SEM images. The results are summarized in Table 4.

Table 4. Measured porosity and hardness of coated QC materials

• 1. Zeiss Axioplan Microscope für die Aufnahme eines optischen Bildes.
• 2. Panasonic WV CD 50, CCD Kamera zur Aufnahme des Bildes.
• 3. SONY Monitor für das Display des digitalisierten Bildes.
• 4. ANTON PAAR MHT-4, Rechner zur Berechnung der Werte der Mikrohärte aus der Eingangslast und den gemessenen Diagonalen.

The devices for measuring the microhardness were as follows:

• 1. Zeiss Axioplan Microscope for taking an optical image.
• 2. Panasonic WV CD 50, CCD camera to take the picture.
• 3. SONY monitor for the display of the digitized image.
• 4. ANTON PAIR MHT-4, computer for calculating the values of the microhardness from the input load and the measured diagonals.

to Examination of the coatings was XRD (x-ray diffraction), SEM (Scanning electron microscopy), EDS (electron diffraction spectroscopy), EPMA (Electron Probe Micro Analysis) and RW-WDX (X-ray fluorescence spectrometry, Philips PW-2400) procedures were used.

It has been shown that the coatings (i) have a decagonal structure, (ii) are dense, (iii) are hard enough and (iv) have good adhesion to the superalloy substrate ( 6 . 7 ).

Claims (27)

Connection of the nominal composition: Al _w Ni _x Ru _y M _z wherein M is at least one of Ir, Pt, Rh, Pd, Cr, V, W, Mo, Nb, Ta, Ti, Hf Zr, Re, Fe, Co, Y, rare earth, Si, B groups , and where w = 68 - 75.0 <x ≦ 25, 0 <y ≦ 25.0 <z ≦ 20 wherein at least 30% by mass of the compound is present as quasicrystalline structure or as approximant. Connection according to claim 1, characterized in that w = 71-74. Connection according to one of the preceding claims, characterized in that x = 10 - 20. Connection according to one of the preceding claims, characterized in that y = 7 - 15. Connection according to one of the preceding claims, characterized in that 1 <z ≤ 10. A compound according to any one of the preceding claims, characterized marked that if M = Co, then z ≤ 15; if M = Fe, then z ≤ 10; if M selected is from the group: Ir, Pt, Rh, Pd or a mixture thereof, then z ≤ 15, preferably z ≤ 10; if M selected is from the group Cr, V, W, Mo, Nb, Ta, Ti, Hf, Zr, Re, or one Mixture thereof, then z ≤ 5, preferably z ≤ 2; if M selected is from the group Y, Si, B or a mixture thereof, then z ≤ 3, preferably z ≤ 1. Compound according to one of the preceding claims, characterized by a nominal composition of one of the following formulas: Al ₇₂ Ni ₁₁ Ru ₁₂ Ir ₅ ; Al ₇₄ Ni ₁₁ Ru ₁₀ Ir ₅ , or a mixture of them Compound according to one of the preceding claims, characterized by a nominal composition of one of the following formulas: al 72 Ni 11 Ru 12 Ir 5 . wherein a decagonal phase based on Al-Ni-Ru-Ir and an approximante phase of the general composition Al ₁₃ Ru ₄ and an intermetallic phase of the general composition Al ₃ Ni ₂ . A compound according to any one of the preceding claims by a solidus temperature of the range 1000-1400 ° C, preferably ≤ 1070 ° C. A compound according to any one of the preceding claims by a parabolic oxidation behavior at a temperature up to 1100 ° C. Compound according to one of the preceding claims, characterized by a thermal conductivity which is lower than 14 Wm ^-1 K ^-1 at room temperature, preferably lower than 6 Wm ^-1 K ^-1 at room temperature. Compound according to one of the preceding claims, characterized by a coefficient of thermal expansion (CTE) of 10-20 × 10 ^-6 K ^-1 , preferably 14-17 × 10 ^-6 K ^-1 in a temperature range from room temperature to 1000 ° C. Coating of a compound according to a of the preceding claims. Layer structure, characterized in that on a substrate, in particular a metallic material or a Superalloy, a coating according to claim 13, in particular as a surface coating, is applied. Layer structure according to claim 14, characterized that between the substrate and the quasicrystalline coating at least one acting as a diffusion barrier, in particular for Al, acting Intermediate layer is arranged. Layer structure according to one of claims 14 or 15, characterized in that the coating based on a A compound according to any one of the claims 1-12 one Thickness of 200-1000 μm, in particular on a superalloy substrate based on Ni or Co or Fe. Layer structure according to one of claims 14-16, characterized characterized in that the intermediate layer is a layer from a pure, especially highly melting Metal as particularly preferably Ru, Ir, Re, Pt, etc. acts. Layer structure according to one of claims 14-17, characterized characterized in that the intermediate layer is a layer from a solid solution from a supreme melting Metal, such as in particular preferably Ru, Ir, Re, Pt, etc., with Al-Ni-Ru-M B2 structure-based intermetallic compounds, where M is one of or more of the elements of both the substrate and the surface coating wherein the intermetallic compound is preferably 26 to 60 atomic% Contains Al, and wherein such an intermediate layer is preferably a melting temperature which has at least 400 ° C is above the operating temperature of the coating. Layer structure according to one of claims 14-18, characterized characterized in that the intermediate layer one or more ceramic Has phases. Layer structure respectively coating after one the claims 13-19 characterized in that the layer structure or the coating on a ceramic thermal barrier coating is arranged, wherein the layer structure respectively the coating particularly preferably has a thickness of 50-300 microns. Layer structure according to one of the preceding claims, characterized characterized in that the ceramic thermal barrier coating yttrium stabilized Contains zirconium. Process for producing a coating according to Claim 13 and a layer structure according to any one of claims 14-21, characterized characterized in that the compound according to any one of claims 1-12 below Use of thermal spray methods such as preferably APS, electroplating, Vapor deposition such as EB-PVD is applied, preferably followed from an aluminizing process. Method according to claim 22, characterized in that that the material is tempered, the annealing preferably before spraying or pulverization. Use of a compound according to any one of claims 1 to 13 preferably as a coating or layer structure according to a the claims 14 to 21 as material for a component which is exposed to high temperatures, and which especially hot gases is exposed respectively from hot Gases flow around becomes. Use of a compound according to claim 24, characterized characterized in that it is a component of a gas turbine or a compressor, more preferably a blade or guide vane of a gas turbine or a compressor. Use according to one of claims 24 or 25, characterized that the compound is particularly preferred as the coating is present directly exposed to the hot gases surface, where appropriate below the coating another functional layer in particular for adhesion or for further barrier action, in particular as a diffusion barrier. Use according to one of claims 24-26, characterized that the coating has a thickness of in the range of 10-400 microns, in particular preferably in the range of 100 to 200 microns.