EP0504048A1 - Wire for coating by torch spraying and its use for depositing a quasi crystalline phase on a substrate - Google Patents

Abstract

The wire (1) comprises a core comprising an organic binder and a powder or a mixture of powders capable of forming a quasicrystalline alloy, this core being surrounded by a sheath of organic material. It thus enables a quasicrystalline alloy to be deposited on a substrate, this alloy being produced in the flame (3) of a spraying device, from commercial powders of the constituents of the quasicrystalline alloy. <IMAGE>

Description

The present invention relates to a bead for coating with a blowtorch projection.

More precisely, it relates to a bead which makes it possible to deposit on a substrate surface coatings of quasi-crystalline alloy, that is to say of alloy having a specific crystallographic structure which results in the presence of at least 30% in mass of an almost crystalline phase.

Aluminum alloys of this type are described, for example, in document EP-A-0 356 287.

• 1) les phases présentant des symétries de rotation normalement incompatibles avec la symétrie de translation, c'est-à-dire des symétries d'axe de rotation d'ordre 5, 8, 10 et 12, ces symétries étant révélées par la diffraction du rayonnement. A titre d'exemple, on peut citer la phase icosaédrique de groupe pontuel m $\overline{\text{3}}$
  
  $\overline{\text{5}}$
  
  (cf. D. Shechtman, I. Blech, D. Gratias, J.W. Cahn, Metallic Phase with Long-Range Orientational Order and No Translational Symmetry, Physical Review Letters, Vol. 53, n° 20, 1984, pages 1951-1953) et la phase décagonale de groupe ponctuel 10/mmm (cf. L. Bendersky, Quasicrystal with One Dimensional Translational Symmetry and a Tenfold Rotation Axis, Physical Review Letters, Vol. 55, n° 14, 1985, pages 1461-1463). Le diagramme de diffraction des rayons X d'une phase décagonale vraie a été publié dans "Diffraction approach to the structure of decagonal quasi crystals, J.M. Dubois, C. Janot, J. Pannetier, A. Pianelli, Physics Letters A 117-8 (1986) 421-427".
• 2) les phases approximantes ou composés approximants qui sont des cristaux vrais dans la mesure où leur structure cristallographique reste compatible avec la symétrie de translation, mais qui présentent, dans le cliché de diffraction d'électrons, des figures de diffraction dont la symétrie est proche des axes de rotation 5, 8, 10 ou 12.

In the present invention, the expression "quasi-crystalline phase" includes

• 1) the phases having rotation symmetries normally incompatible with the translation symmetry, that is to say symmetries of axis of rotation of order 5, 8, 10 and 12, these symmetries being revealed by the diffraction of the radiation. As an example, we can cite the icosahedral phase of the pontial group m $\overline{\text{3}}$
  
  $\overline{\text{5}}$
  
  (cf. D. Shechtman, I. Blech, D. Gratias, JW Cahn, Metallic Phase with Long-Range Orientational Order and No Translational Symmetry, Physical Review Letters, Vol. 53, n ° 20, 1984, pages 1951-1953) and the decagonal phase of the point group 10 / mmm (cf. L. Bendersky, Quasicrystal with One Dimensional Translational Symmetry and a Tenfold Rotation Axis, Physical Review Letters, Vol. 55, n ° 14, 1985, pages 1461-1463). The diffraction diagram of X-rays of a true decagonal phase was published in "Diffraction approach to the structure of decagonal quasi crystals, JM Dubois, C. Janot, J. Pannetier, A. Pianelli, Physics Letters A 117-8 (1986) 421-427 ".
• 2) the approximate phases or approximate compounds which are true crystals insofar as their crystallographic structure remains compatible with the translational symmetry, but which present, in the electron diffraction plate, diffraction figures whose symmetry is close axes of rotation 5, 8, 10 or 12.

Among these phases, there may be mentioned by way of example the orthorhombic phase O₁, characteristic of an aluminum alloy having the atomic composition Al₆₅Cu₂₀Fe₁₀Cr₅ belonging to the alloy compositions described in document EP-A- 0 356 287, the mesh parameters are: a₀ (1) = 2.366, b₀ (1) = 1.267, c₀ (1) = 3.252 in nanometers. This orthorhombic phase O₁ is said to be approximate to the decagonal phase. It is also so close to it that it is not possible to distinguish its X-ray diffraction pattern from that of the decagonal phase.

We can also cite the rhombohedral phase with parameters a _r = 3.208nm, γ = 36 °, present in the alloys of composition close to Al₆₄Cu₂₄Fe₁₂ in number of atoms (M. Audier and P. Guyot, Microcrystalline AlFeCu Phase of Pseudo Icosahedral Symmetry , in Quasicrystals, eds. MV Jaric and S. Lundqvist, World Scientific, Singapore, 1989).

This phase is an approximate phase of the icosahedral phase.

We can also cite O₂ and O₃ orthorhombic phases with respective parameters a₀ (2) = 3.83; b₀ (2) = 0.41; c₀ (2) = 5.26 and a₀ (3) = 3.25; b₀ (3) = 0.41; c₀ (3) = 9.8 in nanometers, present in an alloy of composition Al₆₃Cu _17.5 Co _17.5 Si₂ in number of atoms or also the orthorhombic phase 0₄ of parameters a₀ (4) = 1.46; b₀ (4) = 1.23; c₀ (4) = 1.24 in nanometers, which is formed in the alloy of composition Al₆₃Cu₈Fe₁₂Cr₁₂ in number of atoms.

One can also cite a phase C, of cubic structure, very often observed in coexistence with the approximate or quasi-crystalline phases true. This phase, which forms in certain Al-Cu-Fe and Al-Cu-Fe-Cr alloys, consists of a super-structure, by chemical effect of the alloying elements compared to the aluminum sites, of a phase Cs-Cl type structure and network parameter a₁ = 0.297nm.

A diffraction diagram of this cubic phase has been published (C. Dong, JM Dubois, M. de Boissieu, C. Janot; Neutron diffraction study of the peritectic growth of the Al₆₅Cu₂₀Fe₁₅ icosahedral quasi crystal; J. Phys. Condensed Matter, 2 (1990), 6339-6360) for a sample of pure cubic phase and of composition Al₆₅Cu₂₀Fe₁₅ in number of atoms.

(à 4,5% près) et c_H = $\text{3}\sqrt{\text{3}}$

a₁/2 (à 2,5% près). Cette phase est isotype d'une phase hexagonale, notée Φ AlMn, découverte dans des alliages Al-Mn contenant 40% en poids de Mn (M.A. Taylor, Intermetallic phases in the Aluminium-Manganese Binary System, Acta Metallurgica 8 (1960) 256).One can also cite a phase H of hexagonal structure which derives directly from phase C as demonstrated by the epitaxy relationships observed by electron microscopy between crystals of phases C and H and the simple relationships which connect the parameters of the crystal lattices, namely a _H = $$\text{3}\sqrt{\text{2}}\frac{\text{a₁}}{\sqrt{\text{3}}}$$

(to within 4.5%) and c _H = $\text{3}\sqrt{\text{3}}$

a₁ / 2 (to within 2.5%). This phase is isotype of a hexagonal phase, noted Φ AlMn, discovered in Al-Mn alloys containing 40% by weight of Mn (MA Taylor, Intermetallic phases in the Aluminum-Manganese Binary System, Acta Metallurgica 8 (1960) 256).

The cubic phase, its superstructures and the phases derived therefrom, constitute a class of approximate phases of the quasi-crystalline phases of neighboring compositions.

In addition to their particular crystallographic structure, the alloys comprising these quasi-crystalline phases have specific properties which make them particularly advantageous in the form of surface hardening or protective coatings on various substrates.

Indeed, these alloys have good hardness and friction properties as well as good stability at temperatures above 300 ° C.

Also, they can be used in areas where good abrasion, scratch, impact, erosion and cavitation resistance are sought, as well as protection against oxidation and corrosion. . Other properties such as, for example, their high electrical resistance or even their thermal conduction properties can be usefully exploited in heating devices, including by electromagnetic coupling, or as a thermal barrier.

Until now, to use these quasi-crystalline alloys in the form of coating on a substrate, we first prepared the quasi-crystalline alloy from the various elements, then a powder of this alloy was formed, namely by grinding, or by atomization, and it was then projected onto the substrate using for example a plasma torch.

Although this technique is satisfactory, it has the disadvantage of being expensive when the quantities of quasi-crystalline alloy to be sprayed are low, since it is necessary to have a powder of this alloy manufactured beforehand, while many compositions of 'quasi-crystalline alloy can be considered.

The subject of the present invention is precisely a bead which can be used for forming by blowtorch projection coatings of quasi-crystalline alloy, which makes it possible to avoid this prior operation of manufacturing the alloy and is suitable for producing coatings of quasi-crystalline alloy of any composition fixed in advance.

According to the invention, the bead for coating with a blowtorch projection comprises a core comprising an organic binder and a powder or a mixture of powders capable of forming a quasi-crystalline alloy, this core being surrounded by a sheath of organic material.

Advantageously, the core of the bead additionally contains a mineral binder which makes it possible, during the spraying operation, to bind the powder particles together until their complete melting.

By way of example of a mineral binder, mention may be made of refractory oxide fibers such as alumina fibers.

This cord structure is very advantageous since it is possible to choose the organic binder and the sheath material in an appropriate manner in order to obtain a flexible cord, which makes it possible to continuously supply a projection torch.

In addition, the fact of being able to use in this bead a mixture of powders capable of forming a quasi-crystalline alloy makes it possible to produce any alloy composition by appropriately dosing the quantities of powders placed in the core.

Thus, with the cord of the invention, the production of coatings of quasi-crystalline alloys having various compositions is no longer expensive and can be carried out on demand.

In this bead, the organic binder and the organic material of the sheath are chosen so that they can be easily removed in the torch during the spraying operation, for example by combustion.

By way of example of an organic binder and of organic material which can be used, mention may be made of cellulose derivatives such as methylcellulose, hydroxymethylcellulose, hydroxyethylmethylcellulose and carboxymethylcellulose, and polymers such as polyvinyl alcohol and polymethacrylic acid.

In some cases, the core of the cord comprises water, and / or an organic plasticizer, capable of being easily removed during the spraying operation, for example by evaporation and / or calcination.

By way of example of plasticizer, mention may be made of glycerin, ethylene glycol and triethanolamine. The proportion by weight of organic binder in the core generally does not exceed 4%.

When the core contains an inorganic binder, its content is preferably less than 6% by weight.

• X représente au moins un élément choisi parmi Cu et Co,
• M représente un ou plusieurs éléments du groupe comprenant Fe, Cr, Mn, Ni, Ru, Os, Mo, V, Mg, Zn, Ga et Pd.
• N représente un ou plusieurs éléments du groupe comprenant W, Ti, Zr, Hf, Rh, Nb, Ta, Y, Si, Ge et les terres rares,
• I représente une ou plusieurs impuretés d'alliage,
• a, b, c, d, e et f représentent des pourcentages atomiques tels qu'ils satisfont les relations suivantes :

$$\text{48≦a<92}$$

$$\text{0<b≦30}$$

$$\text{0≦c≦5}$$

$$\text{8≦d≦30}$$

$$\text{0≦e≦4}$$

$$\text{0≦f≦2}$$

$$\text{a+b+c+d+e+f=100}$$

$$\text{b+d+e≦45.}$$

According to a first embodiment of the cord of the invention, the core comprises a single powder capable of forming a quasi-crystalline alloy, this powder can be an alloy powder of composition:

Al _a X _b (BC) _c M _d N _e I _f

in which

• X represents at least one element chosen from Cu and Co,
• M represents one or more elements of the group comprising Fe, Cr, Mn, Ni, Ru, Os, Mo, V, Mg, Zn, Ga and Pd.
• N represents one or more elements of the group comprising W, Ti, Zr, Hf, Rh, Nb, Ta, Y, Si, Ge and the rare earths,
• I represents one or more alloy impurities,
• a, b, c, d, e and f represent atomic percentages such that they satisfy the following relationships:

$$\text{48 ≦ a <92}$$

$$\text{0 <b ≦ 30}$$

$$\text{0 ≦ c ≦ 5}$$

$$\text{8 ≦ d ≦ 30}$$

$$\text{0 ≦ e ≦ 4}$$

$$\text{0 ≦ f ≦ 2}$$

$$\text{a + b + c + d + e + f = 100}$$

$$\text{b + d + e ≦ 45.}$$

This embodiment of the cord of the invention can be used in particular when the quantities of quasi-crystalline alloy to be projected are large and justify the prior preparation of an alloy powder.

In this case, however, the blowtorch spraying operation generally leads to the production of an almost alloy coating. crystalline not having exactly the same composition as the alloy of the powder, but the properties of a quasi-crystalline deposit are nevertheless retained.

$$\text{0<b≦30}$$

$$\text{0≦c≦5}$$

$$\text{8≦d≦30}$$

$$\text{0≦e≦4}$$

$$\text{0≦f≦2}$$

$$\text{a+b+c+d+e+f=100}$$

$$\text{b+d+e≦45}$$

According to a second embodiment of the cord of the invention, the core comprises a mixture of powders capable of forming a quasi-crystalline alloy, for example a mixture of powders of the elements Al, X, B, C, M, N and I with X representing at least one element chosen from Cu and Co, M representing one or more elements of the group comprising Fe, Cr, Mm, Ni, Ru, Os, Mo, V Mg, Zn, Ga and Pd, N representing one or more elements of the group comprising W, Ti, Zr, Hf, Rh, Nb, Ta, Y, Si, Ge and the rare earths, and I representing one or more alloy impurities,
in proportions such that the mixture of powders corresponds to the composition of formula:

Al _a X _b (B, C) _c M _d N _e I _f

in which X, M, N and I have the meaning given above, and a, b, c, d, e and f represent atomic percentages such that they satisfy the following relationships: $$\text{48 ≦ a <92}$$

$$\text{0 <b ≦ 30}$$

$$\text{0 ≦ c ≦ 5}$$

$$\text{8 ≦ d ≦ 30}$$

$$\text{0 ≦ e ≦ 4}$$

$$\text{0 ≦ f ≦ 2}$$

$$\text{a + b + c + d + e + f = 100}$$

$$\text{b + d + e ≦ 45}$$

This second embodiment of the cord of the invention is much more interesting because it makes it easy to manufacture cords for the projection of quasi-crystalline alloys of compositions very varied. Indeed, it suffices to use in this case commercial powders corresponding to the desired elements to produce the core of the bead and to judiciously dose these powders to obtain the desired alloy composition.

In this second embodiment of the cord of the invention, it is also possible to provide at least two elements of the alloy in the form of a combination of these elements, for example in the form of pre-alloyed powder.

The projection cords described above can be prepared by conventional methods, in particular by co-forming two pastes, one of which constitutes the core and the other of which is intended to form the external sheath. A process of this type is described in particular in document FR-A-1 443 142.

According to an alternative embodiment of the invention, the bead for coating with a blowtorch projection comprises a core made of a mixture of inorganic powders and a sheath of inorganic material, the powders of the mixture and the sheath consisting of one or more elements chosen from Al, X, B, C, M, N and I with X representing at least one element chosen from Cu and Co, M representing one or more elements from the group comprising Fe, Cr, Mn, Ni, Ru, Os, Mo, V, Mg, Zn, Ga and Pd, N representing one or more elements of the group comprising W, Ti, Zr, Hf, Rh, Nb, Ta, Y, Si, Ge and the rare earths, and I representing one or several alloy impurities, in proportions such that the assembly (sheath + powder mixture) corresponds to an almost crystalline alloy composition.

In this case, the composition of quasi-crystalline alloys can also correspond to the formula Al _a X _b (B, C) _c M _d N _e I _f in which X, M, N, I, a, b, c, d , e and f have the meanings given above.

In this variant embodiment of the invention, it is possible in particular to produce the steel, Al, Cu or Ni sheath and thus obtain a flexible cored wire also suitable for feeding a torch.

The present invention also relates to a method of depositing on a substrate a coating of quasi-crystalline alloy, which consists in using a spray gun with an oxy-gas flame and / or electric arc or plasma and in supplying this gun with by means of a projection bead as described above, so as to project onto the substrate the almost crystalline alloy obtained by reaction in the flame of the constituents of the bead.

The projection cords of the invention are very advantageous in this process because they make it possible to introduce into the core of the flame of a thermal projection device, all of the elements constituting a quasi-crystalline alloy and to ensure a residence time of these elements inside the flame sufficient to guarantee a complete reaction and the formation of a quasi-crystalline alloy.

The quasi-crystalline alloy thus produced is sprayed with feed gases from the projection device in the form of finely divided droplets on the substrate. When the core of the cord further comprises mineral fibers, for example alumina fibers, these are also projected into the coating formed on the substrate. On the other hand, the organic binder and the sheath of the bead are vaporized during the spraying and they do not intervene either in the reactions of formation of the alloy, or in the coating.

This method of projecting quasi-crystalline alloys has several advantages over the prior art thermal spraying techniques which used powder torches. First of all, it makes it possible to dispense with the operation of atomizing a quasi-crystalline powder of specific composition to replace it with a much simpler operation which consists in mixing common powders readily available to form a paste. In addition, it allows the use of simpler projection devices and wide distribution. Finally, it offers the possibility of composing the mixture of powders at will and consequently of obtaining any desired alloy composition.

The deposits of quasi-crystalline alloy obtained by this process have an increased hardness and improved coefficients of friction compared to many deposits of the current art. Also, these quasi-crystalline deposits are particularly indicated in any tribological application consisting in reinforcing a metal surface of an iron-based alloy, aluminum-based, copper-based or nickel-based.

It is also possible to use the quasi-crystalline deposits of the invention for the production of metal sublayers with a view to metal-metal, metal-ceramic or metal-oxide bonds whose adhesion strength is remarkable. These quasi-crystalline deposits can also be used as bonding layers between a ceramic layer and a layer. oxide.

• la figure 1 est une représentation schématique d'un dispositif de projection utilisable dans l'invention, et
• les figures 2 à 16 sont des diagrammes de diffraction de rayons X caractérisant les alliages quasi cristallins obtenus par projection de cordons conformes à l'invention.

Other characteristics and advantages of the invention will appear better on reading the following description of embodiments, of course given by way of illustration and not limitation, with reference to the appended drawing in which

• FIG. 1 is a schematic representation of a projection device usable in the invention, and
• Figures 2 to 16 are X-ray diffraction diagrams characterizing the quasi-crystalline alloys obtained by projection of beads according to the invention.

In Figure 1, there is shown very schematically, the end of a projection gun using the projection cord of the invention.

In this gun, the projection cord 1 of the invention is introduced into an oxy-gas flame 3 supplied with combustion gas through the channels 5. In this flame 3, the end 1a of the cord which is melted by the flame, reacts in this flame to form the quasi-crystalline alloy and the liquid alloy obtained is sprayed by a gas under pressure, for example by air, introduced by the conduits 7, in the form of droplets which are projected onto a substrate .

In a gun of this type, the combustion gas can be a mixture of hydrogen, acetylene or propane with oxygen and the gas circulating in the pipes 7 can be a jet of pressurized air.

The following examples illustrate the production of compliant projection cords to the invention and their use for producing deposits of quasi-crystalline alloys on mild steel substrates.

Example 1.

In this example, the first embodiment of the invention is used to prepare a projection bead from a quasi-crystalline alloy powder obtained by grinding, in a mixer with concentric rollers of carburetted steel, small ingots of '' a quasi-crystalline alloy having the atomic composition:

Al _62.8 Cu _19.5 Fe _8.5 Cr _9.1 Mn _0.1

• 96% en poids de la poudre d'alliage obtenue par broyage ayant une granulométrie de 20µm à 150µm,
• 4% de fibres de boehmite, et
• 4% de liant organique constitué par de l'hydroxyéthylméthylcellulose.

To prepare the bead, mix thoroughly in a kneader

• 96% by weight of the alloy powder obtained by grinding having a particle size of 20 μm to 150 μm,
• 4% boehmite fiber, and
• 4% organic binder consisting of hydroxyethylmethylcellulose.

From the mixture obtained, a first paste is prepared by adding the sufficient amount of water, then vigorous kneading for one hour.

A second paste is then prepared for use in forming the sheath by kneading the same organic binder as that used for the preparation of the first paste with the sufficient amount of water.

A co-shaping of these two pastes is then carried out in a press to obtain a flexible bead of 4.75mm of external diameter 60m in length having a sheath thickness of 0.012mm.

In Figure 2, the X-ray diffraction diagram at a wavelength of 0.17889nm of the quasi-crystalline alloy of the starting powder. This diagram demonstrates the presence of the decagonal phases C, O₁ and O₃.

Example 2.

In this example, the same procedure is followed as in Example 1 to prepare a projection bead from a quasi-crystalline alloy powder of formula:

Al _65.2 Cu _18.4 Fe _8.2 Cr _8.2

but in this case, one starts from a powder obtained by spraying with an argon jet, having a particle size of 20 to 150 μm.

The X-ray diffraction diagram of the starting alloy is given in Figure 3. It demonstrates the presence in the starting powder of the decagonal phases C, O₁ and O₃.

Example 3.

In this example, the same procedure is followed as in Example 2, to prepare a projection bead in accordance with the first embodiment of the invention, but we start with a quasi-crystalline alloy powder of formula:

Al₇₀Cu₉Fe _10.5 Cr _10.5 .

also obtained by atomization, having a particle size of 20 to 150 μm.

FIG. 4 represents the X-ray diffraction diagram of the starting alloy and demonstrates the presence of the decagonal phases C, O₁ and O₃.

Examples 4 to 9.

In these examples, the second embodiment of the cord of the invention is used, that is to say that the core of the cord is prepared, from powders of the constituents taken separately having the characteristics given in table 1 which follows.

For these preparations, the same procedure is followed as in Example 1, except that the first paste is prepared from a mixture of powders of the various constituents in proportions such that they correspond to the atomic composition given in Table 2, the percentages by weight of powder, fibers and binder being the same as in Example 1. The finely divided aluminum powder was first coated with stearic acid to avoid its oxidation at room temperature.

The cords obtained also have an external diameter of 4.75mm and a sheath thickness of 0.012mm.

Example 10.

In this example, a projection bead corresponding to the variant embodiment of the invention is prepared. In this case, a low-carbon steel sheath 18 mm wide and 0.3 mm thick is used and a mixture of aluminum, copper, iron and chromium powders having on this steel strip having the characteristics given in table 1 to obtain a mixture in which the powder + sheath assembly corresponds to the composition:

Al _65.3 Cu _18.4 Fe _8.2 Cr _8.1 .

The strip is then rolled by mechanical forming to obtain a wire with an external diameter of 4.8mm.

Examples 11 to 29.

• vitesse d'avancement du cordon de 300mm/min ou 1600mm/min, ce qui conduit à des taux d'alimentation massique en poudre du chalumeau proches de 600g/h et de 3,1kg/h, respectivement
• gaz de combustion : hydrogène, acétylène ou propane, avec de l'oxygène ; et
• débits gaz de combustion/O₂ qui varient selon les exemples ; et
• distance de l'origine de la buse du pistolet au substrat : 80 ou 150mm.

In these examples, the projection cords prepared in Examples 1 to 10 are used to make coatings of quasi-crystalline alloys using a wire torch such as than that shown in Figure 1, and operating under the following conditions:

• advancement speed of the bead of 300mm / min or 1600mm / min, which leads to mass powder feed rates of the torch close to 600g / h and 3.1kg / h, respectively
• combustion gases: hydrogen, acetylene or propane, with oxygen; and
• combustion gas / O₂ flow rates which vary according to the examples; and
• distance from the origin of the gun nozzle to the substrate: 80 or 150mm.

In all cases, square platelets of mild steel with a side of 50mm and a thickness of 2mm are used as substrate, which have been previously etched with a jet of corundum.

The deposition conditions used for each example are given in table 3.

After this deposition, the coatings obtained by X-ray diffraction at the wavelength of 0.17889 nm are checked to verify that they correspond to quasi-crystalline alloys.

In Table 3, the quasi-crystalline phases identified in each example and their mass fractions in the coating are reported without taking into account the alumina deposited from the bead.

In view of this table, it can be seen that the projection beads of the invention make it possible to easily obtain the deposition of quasi-crystalline alloys.

FIGS. 5 to 12 are the X-ray diffraction diagrams obtained with the deposits of Examples 11, 12, 14-18 and 20.

In FIG. 5 which relates to Example 11, it can be seen that the diagram is characteristic of the cubic phase C, the diffraction lines of which are identified by C-100, C-110, C-111, C-200, C -210 and C-220, the figures following the letter C corresponding to the Miller indices of the lines.

The other lines which are marked gamma correspond to the aluminum oxide introduced into the deposit from the alumina fibers present in the core of the cord.

• exemple 12 (figure 6),
• exemple 14 (figure 7),
• exemple 15 (figure 8),
• exemple 16 (figure 9),
• exemple 17 (figure 10),
• exemple 18 (figure 11), et
• exemple 20 (figure 12).

FIGS. 6 to 12, the scales of which are not identical to those of FIG. 5, represent the X-ray diffraction diagrams of the deposits obtained in the following examples:

• example 12 (figure 6),
• example 14 (figure 7),
• example 15 (figure 8),
• example 16 (figure 9),
• example 17 (figure 10),
• example 18 (figure 11), and
• Example 20 (Figure 12).

• les diagrammes des figures 6, 8, 9 et 11 sont également caractéristiques de la phase cristalline C,
• la figure 7 est caractéristique des phases cristallines C+H+O₁, et
• les figures 10 et 12 sont caractéristiques des phases cristallines C+H.

In view of these figures, we see that

• the diagrams of FIGS. 6, 8, 9 and 11 are also characteristic of the crystalline phase C,
• FIG. 7 is characteristic of the crystalline phases C + H + O₁, and
• Figures 10 and 12 are characteristic of the crystal phases C + H.

If we compare the X-ray diffraction diagrams of Figures 2, 3 and 4 with those of Figures 5, 6 and 7, respectively, we notice that these latter diagrams are slightly different but that they correspond to an almost crystalline alloy little different from the starting alloy.

In view of Table 3, it is also noted that the rate of quasi-crystalline phase produced as well as to a large extent the nature of these phases does not depend on the deposition parameters, which guarantees the ease of implementation of the process of the present invention.

Example 30.

In this example, the thermal stability of the deposits obtained with the beads of the invention is checked.

For this purpose, these deposits are subjected to two types of heat treatment which are either the isothermal maintenance in secondary vacuum, in a sealed quartz bulb, or the isothermal maintenance in air. These treatments are applied to samples in the form of 1x5 cm plates which have been cut with a diamond saw from mild steel substrates coated with quasi-cristatlin alloy obtained in Examples 11, 15 and 20.

At the end of each heat treatment, the sample is cooled to room temperature by natural air convection. It is then examined by X-ray diffraction. Given the wavelength used (0.17889nm), this technique makes it possible to study the coating materials over a depth of a few micrometers from the exposed surface, which allows to detect modifications which would be due to a surface oxidation.

The results obtained showed that the quasi-crystalline coatings obtained from the beads of the invention were particularly stable.

The processing conditions and the samples tested are given in Table 4 which follows.

FIGS. 13 to 16 are X-ray diffraction diagrams obtained on the samples subjected to the heat treatment.

If we compare the diffraction diagrams of Figures 13, 14, 15 and 16 respectively with the diagrams of Figures 5, 8 and 12, we notice that these diagrams are not modified.

Thus, the quasi-crystalline coatings obtained from the projection cords of the invention are particularly stable. Indeed, no change in structure, which would be revealed by changes in the relative intensity of the diffraction peaks or by the appearance of new lines, is detectable after treatment. Likewise, maintaining the temperature in air, including at 750 ° C., does not increase the intensity of the lines corresponding to the alumina, nor does it give rise to lines characteristic of another oxide.

The coating materials produced from the beads of the invention therefore resist oxidation particularly well, an advantageous property which is added to their great thermal stability.

Example 36.

In this example, the hardness of the coatings of quasi-crystalline alloys obtained in Examples 12, 14 and 24 to 28 is determined.

For this purpose, a portion of the coated substrate wafers obtained in these examples is cut with a diamond saw to take a 40 × 10 mm² test piece. This specimen is then coated with a resin for metallographic use, then it is polished finely for observation with an optical microscope, the specimen having been placed in the coating so that its polished section makes an angle of 40 to 50 °. relative to its surface.

The Vickers hardness is then measured on this polished section of the test piece using a Volpert microdurometer actuated by a load of 400g. The average values obtained from at least ten fingerprints by deposit are given in table 5 appended.

By way of comparison, this table gives the Vickers hardness values also measured under a load of 400 g for quasi-crystalline alloys of the same composition in the form of ingots. This comparison confirms that the projection cords of the invention lead to coatings of high hardness, equivalent to that of the alloys produced in the form of ingots, and this whatever the projection bead used, since the hardnesses are also good when a cord is used, the core of which consists of a mixture of powders of the elements of the almost crystalline alloy.

Example 37.

In this example, the tribological properties of the coatings obtained from the beads of the invention are characterized by determining their coefficient of friction μ which is equal to F _t (N) / F _n (N), that is to say to the relationship between force of resistance F _t in advance of an indenter to which a normal force F _n is applied, both being expressed in Newton.

To measure this coefficient, a CSEM tester (of the pawn / disc type) is used, fitted either with a Vickers diamond indenter or with a Brinell ball made of tool steel 100C6, 1.58mm in diameter. A sample of the steel substrates coated with quasi-crystalline alloy obtained in Examples 12, 14 and 24 to 28 is placed horizontally on the tester, and they are rotated at a uniform speed of one revolution per minute. The indenter is applied with a constant normal force F _n of 5 Newton and a circular stripe with a diameter of 18mm (in the case of the diamond indentor) or 25mm (in the case of the steel Brinell ball). In the case of diamonds, only the first stripe was retained.

The coefficient of friction is determined from the measurement of the resistance force, measured tangentially to the path of the indenter, which therefore includes the cumulative effects of plowing the coating and of the true friction force.

In the case of the Brinell ball, F _t is measured during the first scratch, then the test is continued for 5 additional turns so that the steel indentor finishes digging its groove in the coating. The coefficient of friction is then measured during the fifth round, which then excludes the contribution to friction due to the tabouring of the groove. The coefficient of friction also incorporates the effect which may result from the transfer of material from the coating towards the indenter, because a new ball is used for each test.

It has been noted that this effect is not systematically observed during an examination of the surface of the bead by light microscopy after the test.

On the other hand, a significant increase in the friction force is noted when the porosity of the deposit is high. Indeed, in this case, the displacement of the indentor causes the compaction of the underlying coating material and consequently increases, during the first passages, the contact surface between the indentor and the material and therefore the force resistance to movement of the indenter.

The results obtained are given in Table 6.

In this table, the values of the coefficients of friction obtained in the case of two deposits of 1mm thick made on mild steel substrates using a plasma torch using alloy powders have also been given. quasi-crystalline starting materials used in Examples 2 and 3.

In view of these results, it is noted that the coefficients of friction obtained by projecting the coatings from the beads of the invention are equivalent to the coefficients of friction obtained when the coating is carried out by depositing the alloy by means of a plasma torch.

Example 38.

In this example, the thermal and electrical properties of the quasi-crystalline alloy coating obtained in Example 12, which has a thickness of 3 mm, are determined.

The thermal conductivity is first evaluated using a circuit for measuring the thermal diffusivity.

For this test, the coating of the substrate is first separated by mechanical machining of the latter, then a sample of cylindrical shape 3 mm thick and 10 mm in diameter taken from the coating is irradiated, using a laser beam of energy equal to 20J and 5.10⁻⁶s of pulse duration. The temperature rise which is established on the opposite side of the sample as a function of time is detected by means of an infrared sensor. We then deduce from this measurement the thermal diffusivity α which is related to the thermal conductivity K by the relation K = αC _p d where C _p is the specific heat of the alloy and d its specific mass.

The specific heat was measured at room temperature using a SETARAM scanning calorimeter and the specific mass was obtained by weighing, relative to the volume of the sample.

• α = 1,3.10⁻⁶m²/s
• Cp=600J/kgK
• d=4300kg/m³
• K=3,3W/mK.

The following results were obtained:

• α = 1,3.10⁻⁶m² / s
• Cp = 600J / kgK
• d = 4300kg / m³
• K = 3.3W / mK.

To carry out the electrical measurements, a sample of dimension 1x1 × 10 mm was cut from the quasi-crystalline alloy coating sample of Example 12 separated from its substrate, using an electrolytic saw. The electrical resistivity of this test piece was then measured at room temperature by the so-called 4-point method, using a constant measuring current of 10mA and measuring the voltage at internal electrode terminals with a high-precision nanovoltmeter.

There was thus obtained an electrical resistivity of 3 ohms / meter, or an electrical conductivity of 0.33 ohm⁻¹m⁻¹.

The values of thermal conductivity, on the one hand, and of electrical conductivity, on the other hand, are particularly low for a material which moreover has essentially metallic characteristics.

Also, the deposits of quasi-crystalline alloys of the present invention are particularly interesting for many applications, for example for the realization of thermal barriers, insulation, heating by Joule effect or heating by electromagnetic induction.

Claims (12)

Cord for coating with a blowtorch projection, characterized in that it comprises a core comprising an organic binder and a powder or mixture of powders capable of forming a quasi-crystalline alloy, this core being surrounded by a sheath of organic material. Cord according to claim 1, characterized in that the core additionally contains a mineral binder. Cord according to claim 2, characterized in that the mineral binder consists of alumina fibers. Cord according to any one of claims 1 to 3, characterized in that the powder capable of forming a quasi-crystalline alloy is an alloy powder of composition:

Al _a X _b (B, C) _c M _d N _e I _f

in which - X represents at least one element chosen from Cu and Co, M represents one or more elements of the group comprising Fe, Cr, Mn, Ni, Ru, Os, Mo, V, Mg, Zn, Ga and Pd, N represents one or more elements of the group comprising W, Ti, Zr, Hf, Rh, Nb, Ta, Y, Si, Ge and the rare earths, - I represents one or more alloy impurities, and - a, b, c, d, e and f represent atomic percentages such that they satisfy the following relationships: $$\text{48 ≦ a <92}$$

$$\text{0 <b ≦ 30}$$

$$\text{0 ≦ c ≦ 5}$$

$$\text{8 ≦ d ≦ 30}$$

$$\text{0 ≦ e ≦ 4}$$

$$\text{0 ≦ f ≦ 2}$$

$$\text{a + b + c + d + e + f = 100}$$

$$\text{b + d + e ≦ 45.}$$

Cord according to any one of Claims 1 to 3, characterized in that the mixture of powders capable of forming a quasi-crystalline alloy is a mixture of powders of the elements Al, X, B, C, M, N, and I with X representing at least one element chosen from Cu and Co, M representing one or more elements of the group comprising Fe, Cr, Mn, Ni, Ru, Os, Mo, V, Mg, Zn, Ga and Pd, N representing one or more elements from the group comprising W, Ti, Zr, Hf, Rh, Nb, Ta, Y, Si, Ge and the rare earths, and I representing one or more alloy impurities,
in proportions such that the mixture of powders corresponds to the composition of formula:

Al _a X _b (B, C) _c M _d N _e I _f

in which X, M, N and I have the meaning given above, and a, b, c, d, e and f represent atomic percentages such that they satisfy the following relationships: $$\text{48 ≦ a <92}$$

$$\text{0 <b ≦ 30}$$

$$\text{0 ≦ c ≦ 5}$$

$$\text{8 ≦ d ≦ 30}$$

$$\text{0 ≦ e ≦ 4}$$

$$\text{0 ≦ f ≦ 2}$$

$$\text{a + b + c + d + e + f = 100}$$

$$\text{b + d + e ≦ 45}$$

Cord according to claim 5, characterized in that at least two elements of the composition are present in the mixture of powders in the form of a combination of these. Cord according to any one of claims 1 to 6, characterized in that the sheath and the organic binder consist of a cellulose derivative chosen from methylcellulose, hydroxymethylcellulose, hydroxyethylmethylcellulose and carboxymethylcellulose. Cord according to any one of claims 1 to 7, characterized in that the core further comprises water and / or an organic plasticizer. Cord for coating with a blowtorch projection, characterized in that it comprises a core consisting of a mixture of inorganic powders and a sheath of inorganic material, the powders of the mixture and the sheath consisting of one or more elements chosen from Al , X, B, C, M, N and I with X representing at least one element chosen from Cu and Co, M representing one or more elements from the group comprising Fe, Cr, Mn, Ni, Ru, Os, Mo, V, Mg, Zn, Ga and Pd, N representing one or more elements of the group comprising W, Ti, Zr, Hf, Rh, Nb, Ta, Y, Si, Ge and the rare earths, and I representing one or more impurities of alloy, in proportions such that the assembly (sheath + mixture of powders) corresponds to an almost crystalline alloy composition. Cord according to claim 9, characterized in that the quasi-crystalline alloy composition corresponds to the formula:

Al _a X _b (B, C) _c M _d N _e I _f

in which X, M, N and I have the meaning given above and a, b, c, d, e and f represent atomic percentages such that they satisfy the following relationships: $$\text{48 ≦ a <92}$$

$$\text{0 <b ≦ 30}$$

$$\text{0 ≦ c ≦ 5}$$

$$\text{8 ≦ d ≦ 30}$$

$$\text{0 ≦ e ≦ 4}$$

$$\text{0 ≦ f ≦ 2}$$

$$\text{a + b + c + d + e + f = 100}$$

$$\text{b + d + e <45.}$$

Cord according to claim 10, characterized in that the sheath is made of steel, aluminum, copper or nickel. Process for depositing on a substrate a coating of quasi-crystalline alloy, characterized in that it consists in using a spray gun with oxy-gas flame and / or electric arc or plasma and in supplying this gun by means of a bead according to any one of claims 1 to 12, so as to project onto the substrate the quasi-crystalline alloy obtained by reaction in the flame of the constituents of the bead.

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