Method for coating a substrate surface and coated product

1 187110/2

Method for coating a substrate surface and coated product

The present invention relates to a method of applying coatings which contain only small amounts of gaseous impurities, in particular oxygen.

The application of refractory metal coatings to surfaces exhibits numerous problems.

In conventional processes, the metal is completely or partially melted in most cases, as a result of which the metals readily oxidise or absorb other gaseous impurities.For this reason, conventional processes such asdeposition-welding and plasma spraying must be carried outunder a protecting gas or in vacuo.

In such cases, the outlay in terms of apparatus is high, the size of the components is limited, and the content ofgaseous impurities is still unsatisfactory.

The pronounced introduction of heat transmitted into the object to be coated leads to a very high potential for distortion and means that these processes cannot be employed in the case of complex components, which often also contain constituents that melt at low temperatures.

Complex components must therefore be taken apart before they are re-processed, with the result, in general, that re-processing is scarcely economical and only recycling ofthe material of the components (scrapping) is carried out.

Moreover, in the case of vacuum plasma spraying, tungsten and copper impurities, which originate from the electrodes WO 2006/117144 PCT/EP2006/003967 - 2 - used, are introduced into the coating, which is generallyundesirable. In the case of, for example, the use oftantalum or niobium coatings for corrosion protection,such impurities reduce the protective effect of thecoating by the formation of so-called micro-galvaniccells.

Moreover, such processes are processes of melt metallurgy,which always involve the inherent disadvantages thereof,such as, for example, unidirectional grain growth. Thisoccurs in particular in laser processes, where a suitablepowder is applied to the surface and melted by means of alaser beam. A further problem is the porosity, which canbe observed in particular when a metal powder is firstapplied and is subsequently melted by means of a heatsource. Attempts have been made in WO 02/064287 to solvethese problems by merely melting on the powder particlesby means of an energy beam, such as, for example, laserbeams, and sintering them. However, the results are notalways satisfactory and a high outlay in terms ofapparatus is required, and the problems associated withthe introduction of a reduced but nevertheless high amountof energy into a complex component remain. WO-A-03/106,051 discloses a method and an apparatus forlow pressure cold spraying. In this process a coating ofpowder particles is sprayed in a gas substantially atambient temperatures onto a workpiece. The process isconducted in a low ambient pressure environment which isless than atmospheric pressure to accelerate the sprayed_ WO 2006/117144 PCT/EP2006/003967 - 3 - powder particles. With this process a coating of a powderis formed on a workpiece. EP-A-1,382,720 discloses another method and apparatus forlow pressure cold spraying. In this process the target tobe coated and the cold spray gun are located within avacuum chamber at pressures below 80 kPa. With thisprocess a workpiece is coated with a powder.

In view of this prior art it was therefore the object, toprovide a novel process for coating substrates which isdistinguished by the introduction of a'small amount ofenergy, a low outlay in terms of apparatus and broadapplicability for different carrier materials and coatingmaterials, and wherein the metal to be applied is notmelted on during processing.

Another object of this invention was the provision of anovel process for preparing dense and corrosion resistantcoatings, especially tantalum coatings, which possess lowcontent of impurities, preferably low content of oxygenand nitrogen impurities, which coatings are highlyqualified for use as corrosion protective layer,especially in equipment of chemical plants.

The object of the present invention is achieved byapplying a desired refractory metal to the desired surfaceby a method as claimed in claim 1.

There are generally suitable for this purpose processes inwhich, in contrast to the conventional processes of WO 2006/117144 PCT/EP2006/003967

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thermal spraying {flame, plasma, high-velocity flame, arc,vacuum plasma, low-pressure plasma spraying) and ofdeposition-welding, there is no melting on of the coatingmaterial, caused by thermal energy produced in the coating 5 apparatus. Contact with a flame or hot combustion gases isto be avoided, because these can cause oxidation of thepowder particles and hence the oxygen content in theresulting coatings rises. 10 These processes are known to the person skilled in the artas, for example, cold gas spraying, cold spray processes,cold gas dynamic spraying, kinetic spraying and aredescribed, for example, in EP-A-484533. Also suitableaccording to the invention is the process described in 15 patent DE-A-10253794 .

The so-called cold spray process or the kinetic sprayprocess are particularly suitable for the method accordingto the invention; the cold spray process, which is 20 described in EP-A-484533, is especially suitable, and thisspecification is incorporated herein by reference.

Accordingly, there is advantageously employed a method forapplying coatings to surfaces, wherein a gas flow forms a 25 gas-powder mixture with a powder of a material selectedfrom the group consisting of niobium, tantalum, tungsten,molybdenum, titanium, zirconium, mixtures of at least twothereof or their alloys with one another or with othermetals, the powder has a particle size of from 0.5 to 150 30 μτη, wherein a supersonic speed is imparted to the gas flowand a jet of supersonic speed is formed, which ensures a WO 2006/117144 PCT/EP2006/003967 - 5 - speed of the powder in the gas-powder mixture of from 300to 2000 m/s, preferably from 300 to 1200 m/s, and the jetis directed onto the surface of an object.

The metal powder particles striking the surface of theobject form a coating, the particles being deformed veryconsiderably.

The powder particles are advantageously present in the jetin an amount that ensures a flow rate density of theparticles of from 0.01 to 200 g/s cm2, preferably 0.01 to100 g/s cm2, very preferably 0.01 g/s cm2 to 20 g/s cm2, ormost preferred from 0.05 g/s cm2 to 17 g/s cm2.

The flow rate density is calculated according to theformula F = m/(n/4*D2) where F = flow rate density, D =nozzle cross-section, m - powder feed rate. A powder feedrate of, for example, 70 g/min = 1.1667 g/s is a typicalexample of a powder feed rate.

At low D values of below 2 mm values of markedly greaterthan 20 g/s cm2 can be achieved. In this case F can easilyassume values 50 g/s cm2 or even higher at higher powderdelivery rates.

As the gas with which the metal powder forms a gas-powdermixture there is generally used an inert gas such asargon, neon, helium, nitrogen or mixtures of two or morethereof. In particular cases, air may also be used. Ifsafety regulations are met also use of hydrogen ormixtures of hydrogen with other gases can be used. WO 2006/117144 PCT/EP2006/003967

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In a preferred version of the process the sprayingcomprises the steps of: - providing a spraying orifice adjacent a surface to be 5 coated by spraying; - providing to the spraying orifice a powder of aparticulate material chosen from the group consistingof niobium, tantalum, tungsten, molybdenum, titanium,zirconium, mixtures of at least two thereof or alloys 10 thereof with one another or other metals, the powder having a particle size of 0.5 to 150 pm, said powderbeing under pressure; - providing an inert gas under pressure to the sprayingorifice to establish a static pressure at the 15 spraying orifice and providing a spray of said particulate material and gas onto the surface to becoated; and locating the spraying orifice in a region of lowambient pressure which is less than 1 atmosphere and 20 which is substantially less than the static pressure at the spraying orifice to provide substantialacceleration of the spray of said particulatematerial and gas onto said surface to be coated. 25 In another preferred version of the process the sprayingis performed with a cold spray gun and the target to becoated and the cold spray gun are located within a vacuumchamber at pressures below 80 kPa, preferably between 0.1_and 50 kPa, and most preferred between 2 and 10 kPa. 30 Further advantageous embodiments can be found in theclaims. WO 2006/117144 PCT/EP2006/003967

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In general, the refractory metal has a purity of 99% ormore, such as 99.¾% or 99.7% or 99.9%. 5 According to the invention, the refractory metal advantageously has a purity of at least 99.95%, based onmetallic impurities, especially of at least 99.995% or ofat least 99.999%, in particular of at least 99.9995%.

If an alloy is used instead of a single refractory metal, 10 then at least the refractory metal, but preferably the alloy as a whole, has that purity, so that a correspondinghighly pure coating can be produced.

In addition, the metal powder has an oxygen content of 15 less than 1000 ppm oxygen, or less than 500, or less than300, in particular an oxygen content of less than 100 ppm.

Particularly suitable refractory metal powders have apurity of at least 99.7%, advantageously of at least 20 99.9%, in particular 99.95%, and a content of less than 1000 ppm oxygen, or less than 500 ppm oxygen, or less than300 ppm oxygen, in particular an oxygen content of lessthan 100 ppm. 25 Particularly suitable refractory metal powders have apurity of at least 99.95%, in particular of at least99.995%, and a content of less than 1000 ppm oxygen, orless than 500 ppm oxygen, or less than 300 ppm oxygen, inparticular an oxygen content of less than 100 ppm. 30 Particularly suitable refractory metal powders have apurity of at least 99.999%, in particular of at least WO 2006/117144 PCT/EP2006/003967

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99.9995%, and a content of less than 1000 ppm oxygen, orless than 500 ppm oxygen, or less than 300 ppm oxygen, inparticular an oxygen content of less than 100 ppm. 5 In all the above-mentioned powders, the total content ofother non-metallic impurities, such as carbon, nitrogen orhydrogen, should advantageously be less than 500 ppm,preferably less than 150 ppm. 10 In particular, the oxygen content is advantageously 50 ppmor less, the nitrogen content is 25 ppm or less and thecarbon content is 25 ppm or less.

The content of metallic impurities is advantageously 500 15 ppm or less, preferably 100 ppm or less and most preferably 50 ppm or less, in particular 10 ppm or less.

Suitable metal powders are, for example, many of therefractory metal powders which are also suitable for the 20 production of capacitors.

Such metal powders can be prepared by reduction ofrefractory metal compound with a reducing agent andpreferably subsequent deoxidation. Tungsten oxide or 25 molybdenum oxide, for example, is reduced in a stream ofhydrogen at elevated temperature. The preparation isdescribed, for example, in Schubert, Lassner, "Tungsten",Kluwer Academic/Plenum Publishers, New York, 1999 orBrauer, "Handbuch der Praparativen Anorganischen Chemie", 30 Ferdinand Enke Verlag Stuttgart, 1981, p 1530. WO 2006/117144 PCT/EP2006/003967 - 9 -

In the case of tantalum and niobium, the preparation is inmost cases carried out by reducing alkali heptafluoro-tantalates and earth alkaline metal heptafluoro-tantalatesor the oxides, such as, for example, sodium heptafluorotantalate, potassium heptafluorotantalate,sodium heptafluoroniobate or potassium heptafluoroniobate,with an alkali or alkaline earth metal. The reduction canbe carried out in a salt melt with the addition of, forexample, sodium, or in the gas phase, calcium or magnesiumvapour advantageously being used. It is also possible .tomix the refractory metal compound with the alkali oralkaline earth metal and heat the mixture. A hydrogenatmosphere may be advantageous. A large number of suitableprocesses is known to the person skilled in the art, asare process parameters from which suitable reactionconditions can be selected. Suitable processes aredescribed, for example, in US 4483819 and WO 98/37249.

After the reduction, deoxidation is preferably carriedout. This can be effected, for example, by mixing therefractory metal powder with Mg, Ca, Ba, La, Y or Ce andthen heating, or by heating the refractory metal in thepresence of a getter in an atmosphere that allows oxygento pass from the metal powder to the getter. Therefractory metal powder is in most cases then freed of thesalts of the deoxidising agent using an acid and water,and is dried.

It is advantageous if, when using metals to lower theoxygen content, the metallic impurities can be kept low. WO 2006/117144 PCT/EP2006/003967 - 10 - A further process for preparing pure powder having a lowoxygen content consists in reducing a refractory metalhydride using an alkaline earth metal as reducing agent,as disclosed, for example, in WO 01/12364 and EP-A-1200218.

The thickness of the coating is usually more than 0.01 mm.Preferred are layers with a thickness between 0.05 and 10mm, more preferred between 0.05 and 5 mm, still morepreferred between 0,05 and 1 mm, still more preferred,between 0,05 and 0.5 mm. The thickness may be higher aswell, for example from 3 to 50 mm, or from 5 to 45 mm, orfrom 8 to 40 mm, or from 10 to 30 mm or from 10 to 20 mmor 10 to 15 mm.

The purities and oxygen contents of the resulting coatingsshould deviate not more than 50 % and preferably not morethan 20% from those of the powder.

Advantageously, this can be achieved by coating thesubstrate surface under an inert gas. Argon isadvantageously used as the inert gas because, owing to itshigher density than air, it tends to cover the object tobe coated and to remain present, in particular when thesurface to be coated is located in a vessel which preventsthe argon from escaping or flowing away and more argon iscontinuously added.

The coatings applied according to the invention have ahigh purity and a low oxygen content. Advantageously,these coatings have an oxygen content of less than WO 2006/117144 PCT/EP2006/003967 - 11 - 1000 ppm oxygen, or less than 500, or less than 300, inparticular an oxygen content of less than 100 ppm.

The coatings usually exhibit compressive stress σ.

Usually, the compressive stress is about -1000 MPa to 0MPa, or from -700 MPa to 0 MPa, or from -500 MPa to 0 MPa,of from -400 MPa to 0 MPa or from -300 MPa to 0;

More specifically, the compressive stress is from -200 MPato -1000 MPa, or from -300 MPa to -700 MPa, or from -300MPa to -500 MPa.

In general, a lower oxygen content of the powder employedwill result in layers exhibiting lower compressive stress,e.g. a layer sprayed from powder having an oxygen contentof 1400 ppm will usually result in a layer exhibitingcompressive stress of about -970 ± 50 MPa MPa and a layersprayed from powder having an oxygen content of 270 ppmwill usually result in a layer exhibiting compressivestress of about -460 MPa ± 50 MPa, more preferably -400' MPa ± 50 MPa.

In contrast thereto, layers produced by plasma sprayingresult in layers exhibiting no compressive stress at all,but tensile stress.

In particular, these coatings have a purity of at least99.7%, advantageously of at least 99.9%, in particular ofat least 99.95%, and a content of less than 1000 ppmoxygen, or less than 500 ppm oxygen, or less than 300 ppmoxygen, in particular an oxygen content of less than100 ppm. WO 2006/117144 PCT/EP2006/003967 - 12 -

In particular, these coatings have a purity of at least99.95%, in particular of at least 99.995%, and a contentof less than 1000 ppm oxygen, or less than 500 ppm oxygen,or less than 300 ppm oxygen, in particular an oxygen 5 content of less than 100 ppm.

In particular, these coatings have a purity of 99.999%, inparticular of at least 99.9995%, and a content of lessthan 1000 ppm oxygen, or less than 500 ppm oxygen, or less 10 than 300 ppm oxygen, in particular an oxygen content ofless than 100 ppm.

The coatings according to the invention have a totalcontent of other non-metallic impurities, such as carbon, 15 nitrogen or hydrogen, which is advantageously below 500ppm and most preferably below 150 ppm.

The applied coating has a content of gaseous impuritieswhich differs by not more than 50%, or not more than 20%, 20 or not more than 10%, or not more than 5%, or not morethan 1%, from the content of the starting powder withwhich this coating was produced. The term "differs" is tqbe understood as meaning in particular an increase; theresulting coatings should, therefore, advantageously have 25 a content of gaseous impurities that is not more than 50%greater than the content of the starting powder.

The applied coating preferably has an oxygen content whichdiffers by not more than 5%, in particular not more than 30 1%, from the oxygen content of the starting powder. WO 2006/117144 PCT/EP2006/003967 .1

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The coatings according to the invention preferably have atotal content of other non-metallic impurities, such ascarbon, nitrogen or hydrogen, which is advantageously lessthan 500 ppm and most preferably less than 150 ppm. With 5 the process of this invention layers with higher impuritycontents can also be produced.

In particular, the oxygen content is advantageously 50 ppmor less, the nitrogen content is 25 ppm or less and the 10 carbon content is 25 ppm or less.

The content of metallic impurities is advantageously50 ppm or less, in particular 10 ppm or less. 15 In an advantageous embodiment, the coatings additionallyhave a density of at least 97%, preferably greater than98%, in particular greater than 99% or 99.5%. 97 % densityof a layer means that the layer has a density of 97 % ofthe bulk material. The density of the coating is here a 20 measure of the closed nature and porosity of the coating. A closed, substantially pore-free coating always has adensity of more than 99.5%. The density can be determinedeither by image analysis of a cross-sectional image(ground section) of such a coating, or alternatively by 25 helium pycnometry. The latter method is less preferred because, in the case of very dense coatings, pores presentin coatings that are more remote from the surface are notdetected and a lower porosity is accordingly measured thanactually exists. By means of image analysis, the density 30 can be determined by first determining the total area ofthe coating to be investigated in the image area of the WO 2006/117144 PCT/EP2006/003967 - 14 - microscope and relating this area to the areas of thepores. In this method, pores that are located far from thesurface and close to the interface with the substrate arealso detected. A high density of at least 97%, preferablygreater than 98%, in particular greater than 99% or 99.5%,is important in many coating processes.

The coatings show high mechanical strength which is causedby their high density and by the high deformation of theparticles. In the case of tantalum, therefore, thestrengths are at least 80 MPa more preferably at least 100MPa, most preferably at least 140 MPa when nitrogen isused as the gas with which the metal powder forms a gas-powder mixture. If helium is used, the strength usually isat least 150 MPa, preferably at least 170 MPa, mostpreferably at least 200 MPa and very most preferredgreater than 250 MPa.

Although the coatings according to the invention show highdensities and low porosities, the coatings have amorphology clearly showing it was created from discreteparticles. Examples can be seen,· for example, in Figures 1to 7. In this way the coatings according to the inventioncan be distinguished over coatings obtained by othermethods, like coatings obtained by galvanic processes. Thecharacteristic appearance also allows distinguishing ofcoatings according to the invention from coatings obtainedby plasma spraying.

The articles to be coated with the process of thisinvention are not limited. Generally all articles which WO 2006/117144 PCT/EP2006/003967 need a coating, preferably a corrosion protective coating,can be used. These articles may be .made of metal and/or ofceramic material and/or of plastic material or maycomprise components from these materials. Preferably_ 5 surfaces of materials are coated which are subject toremoval of material, for example by wear, corrosion,oxidation, etching, machining or other stress.

Preferably surfaces of materials are coated with the10 process of this invention which are used in corroding surroundings, for example in chemical processes in medicaldevices or in implants. Examples of apparatus orcomponents to be coated are components used in chemicalplants or in laboratories or in medical devices or as 15 implants, such as reaction and mixing vessels, stirrers,blind flanges, thermowells, birsting disks, birsting diskholders, heat exchangers (shell and tubes), pipings,valves, valve bodies and pump parts. 20 Preferably articles are coated with the process of thisinvention which are no sputter targets or X-ray anodes.

The coatings prepared with the process of this inventionpreferably are used in .corrosion protection. 25

The present invention therefore relates also to articlesmade of metal and/or of ceramic material and/or of plasticmaterial containing at least one coatings composed of therefractory metals niobium, tantalum, tungsten, molybdenum, 30 titanium zirconium or mixtures of two or more thereof or WO 2006/117144 PCT/EP2006/003967 &lt;1 - 16 - alloys of two or more thereof or alloys with other metals,which coatings have the above-mentioned properties.

Such coatings are in particular coatings of tantalum or5 niobium.

Preferably layers of tungsten, molybdenum, titaniumzirconium or mixtures of two or more thereof or alloys oftwo or more thereof or alloys with other metals, very 10 preferably layers of tantalum or niobium, are applied bycold spraying to the surface of a substrate to be coated.Surprisingly it has been found that with said powders orpowder mixtures, preferably with tantalum and niobiumpowders, possessing a reduced oxygen content, for example 15 an oxygen content below 1000 ppm, there can be producedcold sprayed layers with very high deposition rates ofmore than 90 %. In said cold sprayed layers the oxygencontent of the metal is nearly unchanged compared to theoxygen content of the powders. These cold sprayed layers 20 show considerably higher densities than layers produced byplasma spraying or by vacuum spraying. Furthermore, thesecold sprayed layers can be produced without any or withsmall texture, depending on powder properties and coatingparameters. These cold sprayed layers are also 'object of 25 this invention.

Suitable metal powders for use in the methods according tothe invention are also metal powders that consist ofalloys, pseudo alloys and powder mixtures of refractory 30 metals with suitable non-refractory metals. WO 2006/117144 PCT/EP2006/003967 - 17 -

It is thereby possible to coat surfaces of substrates madeof the same alloy or pseudo alloy.

These include especially alloys, pseudo alloys or powdermixtures of a refractory metal selected from the group.consisting of niobium, tantalum, tungsten, molybdenum,titanium, zirconium or mixtures of two or more thereof,with a metal selected from the group cobalt, nickel,rhodium, palladium, platinum, copper, silver and gold.

Such powders belong to the prior art, are known inprinciple to the person skilled in the art and aredescribed, for example, in EP-A-774315 and EP-A-1138420.

They can be prepared by conventional processes; forexample, powder mixtures are obtainable by homogenouslymixing pre-prepared metal powders, it being possible forthe mixing to be carried out on the one hand before use inthe method according to the invention or alternativelyduring production of .the gas-powder mixture. Alloy powdersare in most cases obtainable by melting and mixing thealloying partners. According to the invention there may beused as alloy powders also so-called pre-alloyed powders.These are powders which are produced by mixing compoundssuch as, for example, salts, oxides and/or hydrides of thealloying partners and then reducing them, so that intimatemixtures of the metals in question are obtained. It isadditionally possible according to the invention to usepseudo alloys. Pseudo alloys are understood as beingmaterials which are obtained not by conventional meltmetallurgy but, for example, by grinding, sintering orinfiltration. WO 2006/117144 PCT/EP2006/003967

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Known materials are, for example, tungsten/copper alloysor tungsten/copper mixtures, the properties of which areknown and are listed here by way of example:

Type Density (g/cm3) HB (MPa) Electrical conductivity (% IACS) Thermal expansion coefficient (ppm/K) Thermal conductivity (W/m.K) WCulO 16.8-17.2 £2550 &gt; 27 6.5 170-180 •WCulS 16.3 7.0 190-200 WCu20 15.2-15.6 £2160 &gt; 34 8.3 200-220 WCu25 14.5-15.0 £1940 &gt; 38 9.0 220-250 WCu30 13.8-14.4 £1720 &gt; 42

Also known are molybdenum-copper alloys or molybdenium / 'copper mixtures in the same ratios as indicated above. 10 Also known are molybdenum-silver alloys or molybdenium/silver mixtures which contain, for example, 10, 40 or 65wt.% molybdenum.

Also known are tungsten-silver alloys or tungsten /silver 15 mixtures which contain, for example, 10, 40 or 65 wt.%tungsten.

These can be used, for example, in heat pipes, coolingbodies or, in general, in temperature management systems. 20

It is also possible to use tungsten-rhenium alloys ormixtures, or the metal powder is an alloy having thefollowing composition: WO 2006/117144 PCT/EP2OO6/0O3967 19 - from 94 to 99 wt.%, preferably from 95 to 97 wt.%,molybdenum, from 1 to 6 wt.%, preferably from 2 to 4 wt.%,niobium, from 0.05 to 1 wt.%, preferably from 0.05 to0.02 wt.%, zirconium. 5

These alloys, like pure refractory metal powders having apurity of at least 99.95 %, can be used in the recyclingor production of sputter targets by means of cold gasspraying. 10

Suitable materials for the methods according to theinvention are listed in Tables 1 to 15. Individualmaterials are designated with the number of the tablefollowed by the number of the combination of components 15 and the amount of the non-refractory metal as in Table 1.For example, material 22.005 is a material described inTable 22, the precise composition being defined with thenon-refractory metal and the amount thereof as listed inTable 1, position no. 5. 20

Suitable niobium alloys are listed in Table 1.

Table 1

No. Refractory metal Non-refractory metal Amount of non-refractory metal(wt.%) 1.001 Niobium Cobalt 2-5 1.002 Niobium Nickel 2-5 1.003 Niobium Rhodium 2-5 1.004 Niobium Palladium 2-5 1.005 Niobium Platinum 2-5 1.006 Niobium Copper 2-5 1.007 Niobium Silver 2-5 1.008 Niobium Gold 2-5 1.009 Niobium Cobalt 5-10 1.010 Niobium Nickel 5 -10 1.011 Niobium Rhodium 5-10 WO 2006/117144 PCT/EP2006/003967

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1.012 Niobium Palladium 5-10 1.013 Niobium Platinum 5-10 1.014 Niobium Copper 5-10 1.015 Niobium Silver 5-10 1.016 Niobium Gold 5-10 1.017 Niobium Cobalt 10-15 1.018 Niobium Nickel 10-15 1.019 Niobium Rhodium 10-15 1.020 Niobium Palladium 10-15 1.021· Niobium Platinum 10-15 1.022 Niobium Copper 10-15 1.023 Niobium Silver 10-15 1.024 Niobium Gold 10-15 1.025 Niobium Cobalt 15-20 1.026 Niobium Nickel 15-20 1.027 Niobium Rhodium 15-20 1.028 Niobium Palladium 15-20 1.029 Niobium Platinum 15-20 1.030 Niobium Copper 15-20 1.031 Niobium Silver 15-20 1.032 Niobium Gold 15-20 1.033 Niobium Cobalt 20-25 1.034 Niobium Nickel 20-25 1.035 Niobium Rhodium 20-25 1.036 Niobium Palladium 20-25 1.037 Niobium Platinum 20-25 1.038 Niobium Copper 20-25 1.039 Niobium Silver 20-25 1.040 Niobium Gold 20-25 1.041 Niobium Cobalt 25-30 1.042 Niobium Nickel 25-30 1.043 Niobium Rhodium 25-30 1.044 Niobium Palladium 25-30 1.045 Niobium Platinum 25-30 1.046 Niobium Copper 25-30 1.047 Niobium Silver 25-30 1.048 Niobium Gold 25-30

Table 2: Table 2 consists of 48 alloys, the refractorymetal being tantalum instead of niobium and the non-refractory metal and the amount thereof in wt.% being as 5 indicated in Table 1.

Table 3: Table 3 consists of 48 alloys, the refractorymetal being tungsten instead of niobium and the non-refractory metal and the amount thereof in wt.% being as 10 indicated in Table 1. WO 2006/117144 PCT/EP2006/003967

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Table 4: Table 4 consists of 48 alloys, the refractorymetal being molybdenum instead of niobium and the non-refractory metal and the amount thereof in wt. % being as 5 indicated in Table 1.

Table 5: Table 5 consists of 48 alloys, the refractorymetal being titanium instead of niobium and the non-refractory metal and the amount thereof in wt. % being as 10 indicated in Table 1.

Table 6: Table 6 consists of 48 pseudo alloys, therefractory metal being tantalum instead of niobium and thenon-refractory metal and the amount thereof in wt.% being 15 as indicated in Table 1.

Table 7: Table 7 consists of 48 pseudo alloys, therefractory metal being tungsten instead of niobium and thenon-refractory metal and the amount thereof in wt.% being 20 as indicated in Table 1.

Table 8: Table 8 consists of 48 pseudo alloys, therefractory metal being molybdenum instead of niobium andthe non-refractory metal and the amount thereof in wt.% 25 being as indicated in Table 1.

Table 9: Table 9 consists of 48 pseudo alloys, therefractory metal being titanium instead of niobium and thenon-refractory metal and the amount thereof in wt.% being 30 as indicated in Table 1. WO 2006/117144 PCT/EP2006/003967

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Table 10: Table 10 consists of 48 powder mixtures, therefractory metal being tantalum instead of niobium and thenon-refractory metal and the amount thereof in wt. % beingas indicated in Table 1. 5

Table 11: Table 11 consists of 48 powder mixtures,. therefractory metal being tungsten instead of niobium and thenon-refractory metal and the amount thereof in wt.% beingas indicated in Table 1. 10

Table 12: Table 12 consists of 48 powder mixtures, therefractory metal being molybdenum instead of niobium andthe non-refractory metal and the amount thereof in wt.%being as indicated in Table 1. 15

Table 13: Table 13 consists of 48 powder mixtures, therefractory metal being titanium instead of niobium and thenon-refractory metal and the amount thereof in wt.% beingas indicated in Table 1. 20

Table 14: Table 14 consists of 48 pseudo alloys, therefractory metal being niobium and the non-refractorymetal and the amount thereof in wt.% being as indicated inTable 1. 25

Table 15: Table 15 consists of 48 powder mixtures, therefractory metal being niobium and non-refractory metaland the amount thereof in wt.% being as indicated inTable 1. 30 WO 2006/117144 PCT/EP2006/003967

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Also suitable for use in the methods according to theinvention are metal powders which consist of alloys,pseudo alloys and powder mixtures of different refractorymetals with one another. 5 For example, alloys of molybdenum and titanium in a ratioof 50:50 atomic percent or alloys of tungsten and titaniumin an amount of about 90:10 wt.% are known and aresuitable for use in the methods according to the invention. In principle, however, all alloys of the10 refractory metals with one another are suitable for use in the methods according to the invention.

Binary alloys, pseudo alloys and powder mixtures ofrefractory metals that are suitable for the methods 15 according to the invention are listed in Tables 16 to 36.Individual materials are designated with the number of thetable followed by the number of the combination ofcomponents as in Table 16. For example, material 22.005 isa material described in Table 22, the precise composition 20 being defined by the refractory metals, which are listedin Table 16, position no. 5, and the amount as listed inTable 22.

Component 1 Component 2 16.001 Nb Ta 16.002 Nb W 16.003 Nb MO 16.004 Nb Ti 16.005 Ta Nb 16.006 Ta W WO 2006/117144 PCT/EP20Q6/003967

<img img-format="tif" img-content="drawing" file="IL187110AD000211.tif" id="idf0011" />

- 24 - 16.007 Ta Mo 16.008 Ta Ti 16.009 W Ta 16.010 w Nb 16.011 w Mo 16.012 w Ti 16.013 Mo Ta 16.014 Mo Nb 16.015 Mo W 16.016 Mo Ti 16.017 Ti Ta 16.018 Ti Nb 16.019 Ti W 16.020 Ti Mo

Table 1Ί: Table 17 consists of 20 alloys, pseudo alloysand powder mixtures according to Table 16, component 1being present in an amount of 2-5 wt.%, component 2 being 5 present in an amount ad 100 wt.% and the individualpartners in the mixture being as listed in Table 16.

Table 18: Table 18 consists of 20 alloys, pseudo alloysand powder mixtures according to Table 16, component 1 10 being present in an amount of 5-10 wt.%, component 2 beingpresent in an amount ad 100 wt.% and the individualpartners in the mixture being listed in Table 16.

Table 19: Table 19 consists of 20 alloys, pseudo alloys 15 and powder mixtures according to Table 16, component 1 being present in an amount of 10-15 wt.%, component 2 WO 2006/117144 PCT/EP2006/003967

<img img-format="tif" img-content="drawing" file="IL187110AD000212.tif" id="idf0012" />

- 25 - being present in an amount ad 100 wt.% and the individual partners in the mixture being as listed in Table 16.

Table 20: Table 20 consists of 20 alloys, pseudo alloys5 and powder mixtures according to Table 16, component 1 being present in an amount of 15-20 wt.%, component 2being present in an amount ad 100 wt.% and the individualpartners in the mixture being as listed in Table 16. 10 Table 21: Table 21 consists of 20 alloys, pseudo alloysand powder mixtures according to Table 16, component 1being present in an amount of 20-25 wt.%, component 2being present in an amount ad 100 wt.% and the individualpartners in the mixture being as listed in Table 16. 15

Table 22: Table 22 consists of 20 alloys, pseudo alloysand powder mixtures according to Table 16, component 1being present in an amount of 25-30 wt.%, component 2being present in an amount ad 100 wt.% and the individual 20 partners in the mixture being as listed in Table 16.

Table 23: Table 23 consists of 20 alloys, pseudo alloysand powder mixtures . according to Table 16, component 1being present in an amount of 30-35 wt.%, component 2 25 being present in an amount ad 100 wt.% and the individualpartners in the mixture being as listed in Table 16.

Table 24: Table 24 consists of 20 alloys, pseudo alloys and powder mixtures according to Table 16, component 1 30 being present in an amount of 35-40 wt.%, component 2 WO 2006/117144 PCT/EP2006/003967

<img img-format="tif" img-content="drawing" file="IL187110AD000213.tif" id="idf0013" />

- 26 - being present in an amount ad 100 wt.% and the individual partners in the mixture being as listed in Table 16.

Table 25: Table 25 consists of 20 alloys, pseudo alloys5 and powder mixtures according to Table 16, component 1 being present in an amount of 40-45 wt.%, component 2being present in an amount ad 100 wt.% and the individualpartners in the mixture being as listed in Table 16. 10 Table 26: Table 26 consists of 20 alloys, pseudo alloysand powder mixtures according to Table 16, component 1being present in an amount of 45-50 wt.%, component 2being present in an amount ad 100 wt.% and the individualpartners in the mixture being as listed in Table 16. 15

Table 27: Table 27 consists of 20 alloys, pseudo alloysand powder mixtures according to Table 16, component 1being present in an amount of 50-55 wt.%, component 2being present in an amount ad 100 wt.% and the individual 20 partners in the mixture being as listed in Table 16.

Table 28: Table 28 consists of 20 alloys, pseudo alloysand powder mixtures according to Table 16, component 1being present in an amount of 55-60 wt.%, component 2 25 being present in an amount ad 100 wt.% and the individualpartners in the mixture being as listed in Table 16.

Table 29: Table 29 consists of 20 alloys, pseudo alloys and powder mixtures according to Table 16, component 1 30 being present in an amount of 60-65 wt.%, component 2 WO 2006/117144 PCT/EP2006/003967

<img img-format="tif" img-content="drawing" file="IL187110AD000214.tif" id="idf0014" />

- 27 - being present in an amount ad 100 wt.% and the individual partners in the mixture being as listed in Table 16.

Table 30: Table 30 consists of 20 alloys, pseudo alloys5 and powder mixtures according to Table 16, component 1 being present in an amount of 65-70 wt.%, component 2being present in an amount ad 100 wt.% and the individualpartners in the mixture being as listed in Table 16. 10 Table 31: Table 31 consists of 20 alloys, pseudo alloysand powder mixtures according to Table 16, component 1being present in an amount of 70-75 wt.%, component 2being present in an amount ad 100 wt.% and the individualpartners in the mixture being as listed in Table 16. 15

Table 32: Table 32 consists of 20 alloys, pseudo alloysand powder mixtures according to Table 16, component 1being present in an amount of 75-80 wt.%, component 2being present in an amount ad 100 wt.% and the individual 20 partners in the mixture being as listed in Table 16.

Table 33: Table 33 consists of 20 alloys, pseudo alloysand powder mixtures according to Table 16, component 1being present in an amount of 80-85 wt.%, component 2 25 being present in an amount ad 100 wt.% and the individualpartners in the mixture being as listed in Table 16.

Table 34: Table 34 consists of 20 alloys, pseudo alloys and powder mixtures according to Table 16, component 1 30 being present in an amount of 85-90 wt.%, component 2 WO 2006/117144 PCT/EP2006/003967

<img img-format="tif" img-content="drawing" file="IL187110AD000215.tif" id="idf0015" />

- 28 - being present in an amount ad 100 wt.% and the individual partners in the mixture being as listed in Table 16.

Table 35: Table 35 consists of 20 alloys, pseudo alloys5 and powder mixtures according .to Table 16, component 1 being present in an amount of 90-95 wt.%, component 2being present in an amount ad 100 wt.% and the individualpartners in the mixture being as listed in Table 16. 10 Table 36: Table 36 consists of 20 alloys, pseudo alloysand powder mixtures according to Table 16, component 1being present in an amount of 95-99 wt.%, component 2being present in an amount ad 100 wt.% and the individualpartners in the mixture being as listed in Table 16. 15

Examples

Preparation of a tantalum powder A tantalum hydride powder was mixed with 0.3 wt.% 20 magnesium and placed in a vacuum oven. The oven wasevacuated and filled with argon. The pressure was860 Torr, a stream of argon was maintained. The oventemperature was raised to 650°C in steps of 50°C and, aftera constant temperature had been established, was 25 maintained for four hours. The oven temperature was thenraised to 1000°C iri steps of 50°C and, after a constanttemperature had been established, was maintained for sixhours. At the end of this time, the oven was switched offand cooled to room temperature under argon. Magnesium and 30 the resulting compounds were removed in the conventionalmanner by acid washing. The resulting tantalum powder had WO 2006/117144 PCT/EP2006/003967

<img img-format="tif" img-content="drawing" file="IL187110AD000216.tif" id="idf0016" />

- 29 - a particle size of -100 mesh (&lt; 150 μπι) , an oxygen contentof 77 ppm and a specific BET surface area of 255 cm2/g.

Preparation of a titanium powder5 The procedure was as for the preparation of the tantalum powder. A titanium powder having an oxygen content of93 ppm was obtained.

Preparation of a pre-alloyed titanium/tantalum powder10 A mixture of tantalum hydride powder and titanium hydride powder in a molar ratio of 1:1 was prepared and was mixedwith 0.3 wt.% magnesium; the procedure as in-thepreparation of the tantalum powder was then followed. Atitanium/tantalum powder having an oxygen content of 15 89 ppm was obtained.

Production of coatings

Tantalum and niobium coatings were produced. The tantalum20 powder used was AMPERIT® 150.090 and the niobium powder used was AMPERIT® 160.090, both of which are commerciallyavailable materials from H.C. Starck GmbH in Goslar. Thecommercially available nozzle of the MOC 29 type from CGTGmbH in Ampfing was used. WO 2006/117144 PCT/EP2006/003967

<img img-format="tif" img-content="drawing" file="IL187110AD000217.tif" id="idf0017" />

- 30 -

Material Tantalum Tantalum Niobium Niobium Nozzle MOC 29 MOC 29 MOC 29 MOC 29 Determination of the feed rate at 0.52 Nm’/h: 3.0 rpm (g/30s / g/min) 35.5/71.0 35.5/71.0 14.7/29.4 14.7/29.4 4.0 rpm (g/30s / g/min) 19.8/39.6 19.8/39.6 Movement data: Spray speed / speed of the nozzle over the 20 / 333 20 / 333 20 / 333 20/333 substrate (m/min) (mm/s) Line feed (mm) 1.5 1.5 1.5 1.5 Spraying Interval (mm) 30 30 30 30 Process gas: Nitrogen Helium Nitrogen Hetium Pressure (bar) 30 28 30 28 Flow (Nm3/h) 65 190/He 161 60 190/He 161 Proportion of feed gas (%) 8 3 (N2&gt; 8 3 (N2) Powder feed Powder feed rate (g/min) 71 71 39.6 39.6 Number of passes 3 3 3 3 Substrates 1FTa 1FS 1FV 1FTa1FV2FS 2FS2FV1RS 2FS 2FV1RV 1FS 1RV1RS 1RV1RS 1RV 1RS Sheet thickness before (mm) 2.86 2.92 2.91 2.84 Sheet thickness after (mm) 3.38 3.44 3.35 3.36 Coating thickness, approx, (pm) *) 520.00 520.00 436.00 524.00 Porosity / Density 0.9%/99.1% 2.2% / 97.8%

Substrates: The substrates were placed in succession onthe specimen holder and coated under the indicated test 5 conditions. The substrate description is made up asfollows:

The number at the beginning indicates the number ofidentical substrates located next to one another. The 10 following letter indicates whether a flat specimen (F) ora round specimen (R, tube) was used. The following lettersindicate the material, Ta meaning tantalum, S meaning astructural steel, and V meaning a stainless steel(chromium-nickel steel). 15 WO 2006/117144 PCT/EP2006/003967 - 31 -

Very strong and dense coatings were obtained, whichexhibit low porosity and excellent adhesion to thesubstrates in question. The flow rate densities werebetween 11 and 21 g/sec*cm2.

Figures 1 to 10 show light microscope pictures of cross-sections of the resulting tantalum coatings. No inclusionsof copper or tungsten are detectable, as occurs withcorresponding layers produced by vacuum plasma spraying.The porosity determination was carried out automaticallyby the image analysis program ImageAccess.

Figure 1: Unetched cross-section of a tantalum coating,process gas helium

Figure 2: Unetched cross-section of a tantalum coating,process gas helium, overview picture with lowmagnification

Figure 3: Cross-section of a tantalum coating, etched withhydrofluoric acid, process gas helium, overview picturewith low magnification

Figure 4: Cross-section of a tantalum coating, etched withhydrofluoric acid, process gas helium

Figure 5: Image section used for porosity determination,cross-section of a tantalum coating, process gas heliumFigure 6: Cross-section of a tantalum coating, etched withhydrofluoric acid, interface with the substrate, processgas helium

Figure 7: Unetched cross-section of a tantalum coating,process gas nitrogen, overview picture with lowmagnification WO 2006/317144 PCT/EP2006/003967

<img img-format="tif" img-content="drawing" file="IL187110AD000218.tif" id="idf0018" />

Figure 8: Unetched cross-section of a tantalum coating,process gas nitrogen

Figure 9: Image section used for porosity determination,cross-section of a tantalum coating, process gas nitrogen 5 Figure 10: Unetched cross-section of a tantalum coating,process gas nitrogen, high magnification □'DDt'QTl PPtiZtt , cpnxan rwzn ατα pnow pnszn irn nr qaot ,Ρ’ηη ηχΰ- ηΏοΰΠΒ rw™ m&amp;amp;TOt np’ioz .zruwan tto mpnnn pmf? oxnmοιηπη Pi?

<img img-format="tif" img-content="drawing" file="IL187110AD000219.tif" id="idf0019" />

.(moit παΊηπ) erosion -too