Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C45/00—Amorphous alloys
  • C22C45/08—Amorphous alloys with aluminium as the major constituent
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/06—Alloys based on aluminium with magnesium as the next major constituent
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/12—Alloys based on aluminium with copper as the next major constituent

Definitions

• the present invention relates to alloys, the essential constituent of which is aluminum, the substrates coated with aluminum alloys, and their applications.
• metals or metal alloys for example aluminum alloys
• cooking utensils and appliances are known, anti-friction bearings, chassis or apparatus supports, various parts obtained by molding.
• most of these metals or metal alloys have drawbacks for certain applications, linked to their insufficient hardness and resistance to wear, and to their low resistance to corrosion, in particular in an alkaline medium.
• Various attempts have been made to obtain improved aluminum alloys.
• European patent 100287 describes a family of amorphous or microcrystalline alloys having improved hardness, usable as reinforcing elements of other materials or for obtaining surface coatings improving resistance to corrosion or to wear.
• a large number of the alloys described in this patent are not stable at temperatures above 200 ° C., and during a heat treatment, in particular the treatment to which they are subjected when deposited on a substrate, they change structure: return to the microcrystalline state in the case of essentially amorphous alloys, grain magnification for essential alloys-
• 35 talline or morphological induces a change in the physical characteristics of the material which essentially affects its density. This results in the appearance of micro-cracks, hence a brittleness, which adversely affects the mechanical stability of the materials.
• Thermal stability is an essential property for an alloy to be used as a thermal barrier.
• Thermal barriers are assemblies of one or more materials intended to limit the heat transfer to or from parts and components of equipment in many domestic or industrial devices. For example there may be mentioned the use 'of thermal barriers in the heating or cooking devices, irons at the attachment of the hot part of the carcass and thermal insulation; in cars, at several points such as the turbocharger, the exhaust pipe, the insulation of the passenger compartment, etc .; in aeronautics, for example on the rear of compressors and reactors.
• Thermal barriers are sometimes used in isolation in the form of a screen, but very often they are directly associated with the heat source or with the part to be protected for reasons of mechanical strength.
• mica sheets, ceramic plates, etc. are used in household utensils, adapting them by screwing or gluing, or sheets of agglomerated glass wool supported by a metal sheet.
• a particularly advantageous method for adding a thermal barrier to a part, in particular to a metallic part consists in depositing on a substrate the material constituting the barrier in the form of a layer of thickness determined by a thermal spraying technique such as plasma spraying. for example.
• thermal barrier with other materials also deposited in layers by thermal spraying.
• these other materials can be intended to ensure the protection of the barrier vis-à-vis external aggressions such as for example mechanical shocks, a corrosive medium, etc. or can serve as a sub-layer for bonding to the substrate.
• Mention may be made of alumina which has a specific mass lower than that of zirconia, a diffusivity and a specific heat greater than that of zirconia, but whose mechanical properties are not satisfactory. Mention may also be made of stainless steels and certain refractory steels which offer thermal insulation properties, but which have a high specific mass.
• the object of the present invention is to provide a family of alloys having high hardness and thermal stability, improved ductility and resistance to corrosion.
• the present invention thus relates to a new family of alloys, the essential constituent of which is aluminum.
• the invention also relates to the metallic coatings obtained from these alloys.
• Another object of the invention consists of the substrates coated with said alloys.
• M represents one or more elements chosen from Fe, Cr, Mn, Ni, Ru, Os, Mo, V, Mg, Zn, Pd;
• N represents one or more elements chosen from W, Ti, Zr, Hf, Rh, Nb, Ta, Y, Si, Ge, rare earths; I represents the inevitable processing impurities;
• the expression "quasi-crystal-line phase” includes: 1) the phases having rotation symmetries normally incompatible with 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.
• This orthorhombic phase 0 * ⁇ is said to be approximate to the decagonal phase. It is so close to it that it is not possible to distinguish its X-ray diffraction pattern from that of the decagonal phase.
• This phase is an approximate phase of the icosahedral phase.
• phase C with a cubic structure, very often observed in coexistence with the approximate phases. mantis or quasicrystalline true.
• This phase is isotype of a hexagonal phase, noted 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 quasicrystalline phases of neighboring compositions.
• alloys of the present invention mention may be made of those, hereinafter designated by (II), which have the above-mentioned atomic composition (I) in which 0 ⁇ b ⁇ 5, 0 ⁇ b ' ⁇ 22 and / or 0 ⁇ c ⁇ 5, and M represents Mn + Fe + Cr or Fe + Cr.
• These alloys (II) are more particularly intended for the coating of cooking utensils.
• alloys (VII) having composition (I) and which exhibit improved ductility are those for which c> 0, preferably 0 ⁇ c ⁇ 1, and / or 7 ⁇ b 1 ⁇ 14.
• the alloys of the present invention are distinguished from the alloys of the prior art, and in particular those of EP 356 287 by their copper content which is lower, or even zero. Alloys are therefore less sensitive to corrosion in an acid medium. In addition, the low copper content is more favorable for obtaining improved ductility by adding other elements such as B or C. In the alloys of the present invention, the copper can be replaced in whole or in part by cobalt. These alloys are therefore particularly advantageous with regard to hardness, ductility and resistance to corrosion both in an alkaline medium and in an acid medium in the range of intermediate pHs (5 ⁇ pH ⁇ 7). The combination of these different properties offers the alloys of the present invention a wide range of applications.
• the alloys of the present invention can for example be used as an anti-wear or reference surface coating or for the production of metal-metal or metal-ceramic joints. They are also suitable for all uses involving food contact.
• the alloys of the invention preferably those of the group
• VII can also be used for anti-shock surfaces.
• the alloys according to the invention of groups (III) and (V) are preferably used.
• the alloys of group (III) will preferably be used, whereas those of groups (III) and (IV) are particularly suitable for surfaces resistant to corrosion.
• the alloys of groups (III), (IV) and (VII) are particularly suitable for the production of anti-cavitation or anti-erosion surfaces.
• the materials of the present invention can be used to constitute thermal protection elements of a substrate, in the form of a thermal barrier or in the form of an undercoat of attachment for thermal barriers made of conventional materials. They have good thermal insulation properties, good mechanical properties, a low specific mass, good resistance to corrosion, especially to oxidation, and great ease of use.
• the quasicrystalline alloys of the present invention are therefore suitable substitutes for the replacement of many thermal barrier materials, and in particular of zirconia, with respect to which they have advantages of low specific mass, excellent mechanical properties in this which relates to hardness, improved resistance to wear, abrasion, scratching, as well as corrosion.
• the diffusivity of the materials constituting the thermal protection elements of the present invention is reduced when the porosity of the materials increases.
• the porosity of a quasi-crystalline alloy can be increased by an appropriate heat treatment.
• the materials constituting the thermal protection elements of the present invention may contain a small proportion of heat conducting particles, for example metallic aluminum crystals.
• the thermal conduction of the material will be dominated by the conduction properties of the matrix as long as the particles do not coalesce, that is to say as long as their volume proportion remains below the percolation threshold. For approximately spherical particles with a weakly distributed radius, this threshold is around 20%.
• This condition implies that the material constituting the thermal protection element contains at least 80% by volume of quasi-crystalline phases as defined above. Preferably, therefore, materials containing at least 80% of quasi-crystalline phase are used for their application as a thermal barrier.
• the thermal protection elements can be used as thermal barriers. Such temperature conditions correspond to most domestic or automotive applications. In addition, they have a great ability to resist the stresses due to the expansion of the support and their expansion coefficient is intermediate between that of metal alloys and that of insulating oxides.
• the quasicrystalline alloys constituting the thermal barriers can contain stabilizing elements chosen from W, Zr, Ti, Rh, Nb, Hf and Ta. The content of stabilizing element is less than or equal 2% by number of atoms.
• the thermal barriers of the present invention can be multi-layer barriers having an alternation of layers of materials which are good conductors of heat and layers of materials which are poor conductors which are alloys. almost crystalline.
• Such structures constitute, for example, abradable thermal barriers.
• the thermal protection elements of the present invention can be used as a bonding undercoat for a layer serving as a thermal barrier and constituted by a material. of the prior art such as zirconia. In these temperature ranges, the materials constituting the thermal protection elements of the present invention become super ⁇ plastic. They therefore correspond well to the conditions of use required for the production of a bonding sub-layer while being capable of participating themselves in the isolation of the substrate. Thus, the thermal protection elements of the present invention can be used up to a few tens of degrees from the melting point of the material from which they are made. This limit is around 950 ° C to 1200 ° C depending on the composition.
• the alloys according to the invention can be obtained by conventional metallurgical production processes, that is to say which comprise a slow cooling phase (ie ⁇ T / t less than a few hundred degrees).
• ingots can be obtained by melting separate metallic elements or pre-alloys in a graphite crucible brazed under a protective gas blanket (argon, nitrogen), a blanket flux used in conventional metallurgy ⁇ ration, or in a crucible kept under vacuum. It is also possible to use refractory ceramic or copper crucibles cooled by high frequency current heating.
• the preparation of the powders necessary for the metallization process can be carried out for example by mechanical grinding or by ato isation of the liquid alloy in a jet of argon according to a conventional technique.
• the alloying and atomizing operations can be carried out in sequence without requiring the casting of intermediate ingots.
• the alloys thus produced can be deposited in thin form, generally up to a few tens of micrometers, but also in thick form, up to several millimeters, by any metallization technique, including those which have already been mentioned.
• the alloys of the present invention can be used in the form of a surface coating by deposition from a pre-prepared ingot, or of ingots of the separate elements, taken as targets in a sputtering reactor, or also by vapor phase deposition. produced " by vacuum melting of the solid material. Other methods, for example those which employ sintering of agglomerated powder, can also be used.
• the coatings can also be obtained by thermal spraying, for example using an oxy-gas torch, a super-sonic torch or a plasma torch The thermal spray technique is particularly interesting for the development of thermal protection elements.
• the hardness of the alloys was determined using the WOLPERT V-Testor 2 durometer under loads of 30 and 400 grams.
• An estimate of the ductility of certain alloys was obtained by measuring the length of the cracks formed from the angles of the cavity under load of 400 grams. An average value of this length, as well as the hardness, was evaluated from at least 10 different fingerprints distributed on the sample. Another estimate of the ductility is based on the amplitude of the deformation produced before rupture during a compression test applied to a cylindrical specimen of 4.8 mm in diameter and 10 mm in height machined with perfectly parallel faces perpendicular to the cylinder axis. An INSTROM brand traction / compression machine was used.
• the electrical resistivity of the samples was measured at room temperature on cylindrical specimens 20 mm long and 4.8 mm in diameter.
• the conventional method known as 4 points was used, with a constant measuring current of 10 A.
• the voltage across the internal electrodes was measured with a high precision nanovoltmeter.
• a measurement was made as a function of the temperature using a specifically adapted oven.
• the melting temperatures of some alloys were determined on heating with a speed of 5 ° C / min by Differential Thermal Analysis on a SETARAM 2000C device.
• the crystallographic structure of the alloys was defined by analysis of their X-ray diffraction diagram and their electron diffraction diagrams.
• Example 1 Development of Quasicrystalline Alloys
• a series of alloys was produced by melting pure elements in a high frequency field under an argon atmosphere in a cooled copper crucible.
• the total mass thus produced was between 50 g and 100 g of alloy.
• the melting temperature which depends on the composition of the alloy, has always been found in the temperature range between 950 and 1200 a C.
• a cylindrical test tube full of 10 mm + 0.5 mm in diameter and a few centimeters in height was formed by aspiration of the molten metal in a quartz tube. The the cooling rate of this sample was close to 250 ° C per second.
• This sample was then cut with a diamond saw to shape the metallography and hardness specimens used in the examples below. Part of the test piece was fragmented for thermal stability tests and a crushed powder fraction for X-ray diffraction analysis of each alloy. A similar assembly was used to obtain the 4.8 mm diameter cylindrical samples intended for electrical resistivity. The cooling rate of the specimen was then close to 1000 ° C per second.
• Table 1 below gives the quasicrystalline phase content of the alloys according to the invention obtained, as well as the melting temperature of some of them.
• the X-ray diffraction patterns and the electron diffraction patterns were recorded for the quasicrystalline alloys listed in Table 1. Their study made it possible to determine the crystallographic nature of the phases present. This is how, for example, alloys 2, 5, 7, 8, 9, 19, 22 mainly have the O * phase. and the alloy 1 ma mainly phase C.
• the alloy 3 mainly contains phase H.
• the alloy 6 consists essentially of phase H, as well as a small fraction of phase C.
• the other alloys contain varying proportions of phases C, 0 * ⁇ , O 3 , O4 (and H for 23).
• a bath of one hundred (100) kilograms of an alloy producing a mass fraction of more than 95% of quasicrystalline phase has been developed.
• the nominal composition of the alloy was Al 6 7Cu9 f 5Fei 2 Cr * n ( 5 in number of atoms (alloy 39).
• tion was made from industrial metallic components, namely aluminum A5, a Cu-Al-Fe alloy containing 19.5% Al by weight, 58.5% Cu by weight and 21.5 % Fe by weight.
• These elements and alloys were introduced cold into a graphite crucible brazed with alumina. Their merger was carried out under a hedging flow which was maintained until the end of the operation.
• a high frequency generator of 125 k was used.
• the specific heat of the alloy was determined in the temperature range 20-80 "C with a SETARAM scanning calorimeter.
• the thermal diffusivity of a pellet of this alloy 15 mm thick and 32 mm in diameter was deduced from the temperature / time curve measured on one face of the patch, knowing that the opposite face, previously blackened, was irradiated by a laser flash of calibrated power and shape.
• the thermal conductivity is deduced from the two previous measurements, knowing the specific gravity of the alloy which has been measured by the Archimedes method by immersion in butyl phthalate maintained at 30 "C (+ 0.1 ° C) and found equal to 4.02 g / cm 3 . Comparative Example 3
• Thermal stability The thermal stability of some alloys of the present invention has been evaluated.
• the selected alloys were subjected to maintenance at different temperatures for periods ranging from a few hours to several tens of hours.
• Fragments extracted by breaking the ingots prepared according to Example 1 were placed in quartz ampoules sealed under secondary vacuum. The volume of these fragments was of the order of 0.25 cm 3 .
• the ampoules were placed in an oven previously heated to the treatment temperature. At the end of the treatment, they were cooled under vacuum to ambient temperature by natural convection in air or at a controlled speed. The fragments were then ground for X-ray diffraction examination. Electron diffraction examinations were also carried out.
• the experimental conditions of the heat treatments are summarized in table 3 below.
• the alloys of the present invention are thermally stable in the sense that their structure, as it is charac ⁇ terized by the appropriate diffraction figures, does not change essentially during isothermal heat treatments at temperatures which can reach the melting temperature of the alloys. In other words, the mass fraction of quasicrystalline phase present in the raw state of production does not decrease during temperature maintenance.
• Example 5 Oxidation resistance Samples in fragments identical to those described in Example 4 were subjected to heat treatments in an oven open to air, under conditions summarized in Table 4 below.
• Example 6 Morphology and Grain Size
• the alloys of the present invention are polycrystalline materials whose morphology has been studied by optical microscopy according to a conventional metallography technique.
• the 10 mm diameter pellets produced according to the method of Example 1 were finely polished and then attacked with an appropriate metallographic reagent.
• the metallographic images were photographed with an Olympus optical microscope, working in white light.
• the grain size observed is between a few micrometers and a few tens of micrometers.
• the same characterization method was applied to the samples treated with air in the temperature range 400 "C to 500 ° C as described in Table 4 of the example above. give in.
• the Vickers hardnesses of the alloys of the present invention and of certain alloys of the prior art were measured at room temperature on fragments of alloys produced according to the method of Example 1, coated in a resin for metallographic use, then finely polished. Two loads of the microdurometer, respectively 30g and 400g, were used. The results are given in Table 5 below.
• the Vickers hardnesses observed for the alloys of the present invention are particularly high in comparison with the Vickers hardnesses under load of 400 grams recorded for the alloys of the prior art prepared as in Example 3 (sample 41 to 46).
• the ductility of alloys with high hardness is relatively low.
• the alloys of the present invention containing cobalt have a higher ductility.
• additions for example of boron or carbon.
• compositions 41 to 46 and 40 are alloys of the prior art, the others are alloys according to the invention.
• the compositions of the prior art have an electrical resistivity at room temperature which is between a few ⁇ cm and a few tens of ⁇ cm.
• alloy 42 of composition Al ⁇ sCris in number of atoms which has a resistivity of 300 ⁇ cm. This value is to be compared with the presence of a rate of quasicrystalline phase fairly close, although lower, of 30% by mass. This state is however metastable and has only been achieved thanks to the high cooling rate which characterizes the method of preparation of the present test pieces.
• the characteristic values of the electrical resistivity of the alloys of the present invention are between 300 and 600 ⁇ cm.
• Such high values mean the quasicrystalline alloys of the present invention for any application where this property must be taken advantage of, such as, for example, Joule heating, resistors with high heat dissipation, electromagnetic coupling, possibly high frequency.
• an alloy representative of the family (III) has a low temperature coefficient of electrical resistivity (1 / p dp / dT).
• the relative variation of the electrical resistivity with the temperature of a test tube of alloy 2 was measured.
• This test tube was prepared from a tape 0.1 mm thick and 1.2 mm wide. produced by quenching the liquid alloy on a copper drum, the surface of which scrolled at a speed of 12 m / s (technique, known as melt spinning).
• the ingot brought to the liquid state had been prepared according to the method of example 1.
• the test piece was heated at a constant speed of 5 ° C./minute and kept in contact with four platinum wires according to the so-called measurement method. in four points.
• the difference between potential electrodes was 20 mm and the potential measurement carried out with a precision nanovoltmeter.
• a constant current of 10 A flowed through the test tube through the other two electrodes.
• the measuring device was kept under a protective argon flow in a suitable oven. It was found that the variation in resistance is linear, which demonstrates that no transformation of the sample takes place during the measurement or during the following heating cycle, in confirmation of the great thermal stability of the alloys (example 4).
• the temperature coefficient deduced from the curve (l / ⁇ (20 ° C)) (p (T) -p (20 ° C)) / ⁇ T is -3.10 - ***. This low value distinguishes the alloy for applications where it is preferable to keep the characteristics of the material within a narrow range as a function of the temperature, such as for example heating by electromagnetic induction.
• Example 9 Corrosion resistance The dissolution of certain alloys of the present invention in different media was measured as well as that of an alloy of the prior art.
• test tube 10 mm in diameter and 3 mm thick prepared according to the procedure of Example 1, was immersed for 30 h in a corrosive solution, at different temperatures. The solution was stirred for the duration of the immersion and kept at temperature by a thermostatically controlled bath. After 30 hours, the weight loss of each test piece was determined.
• the present invention provides alloys which have excellent corrosion resistance in an acid medium (No. 2, having a Cu content greater than 5 atomic%), or in a strongly alkaline medium (No. 3 and 6, having a cobalt content greater than 5 atomic%).
• the quasicrystalline alloys of the present invention combine several properties which designate them very particularly for many applications in the form of surface coatings: high hardness, low but not negligible ductility, thermal stability, high resistance to corrosion.
• high hardness low but not negligible ductility
• thermal stability high resistance to corrosion.
• these alloys retain these properties after they have been used as a surface coating. They then have a coefficient of friction remarkably weak which enriches the range of interesting properties already mentioned.
• An ingot of two kilograms of the alloy produced according to Example 2 was reduced to powder by grinding using a mill with carbide steel concentric rollers.
• the " powder thus obtained was sieved so as to retain only the fraction of grains whose size was between 25 ⁇ m minimum and 80 ⁇ m maximum.
• a deposit of 0.5 mm thick was then produced by spraying this powder onto a mild steel plate previously sandblasted. This spraying was carried out by means of a Metco flame torch fed by a mixture dosed with 63% hydrogen and 27% oxygen.
• Example 11 Thermal diffusivity at room temperature.
• the thermal diffusivity, the specific mass d and the specific heat Cp were determined in the vicinity of room temperature for several samples prepared according to Example 1 and one sample prepared according to Example 2.
• the samples prepared according to the method of 1 ' Example 1 are pellets 10 mm in diameter and 3 mm thick.
• the sample of Example 2 is a pellet 32 mm in diameter and 15 mm thick.
• test pieces The opposite faces of each pellet have been polished mechanically under water, taking great care to guarantee their parallelism.
• the structural state of the test pieces was determined by X-ray diffraction and by electron microscopy. All selected samples contained at least 90% quasicrystalline phase volume according to the definition given above.
• the thermal diffusivity has been determined using a laboratory device combining the laser flash method with an Hg-Cd-Te semiconductor detector. The laser was used to supply pulses of power between 20 J and 30 J with a duration of 5.10 "4 s, to heat the front face of the specimen and the semiconductor thermometer was used to detect the thermal response on the opposite side of the specimen. The thermal diffusivity was deduced from the experiments according to the method described in "A. Degiovanni, High Te p. - High Pressure, 17 (1985) 683.
• the specific heat of the alloy was determined in the temperature range 20-80 ° C with a SETARAM scanning calorimeter.
• the thermal conductivity ⁇ is deduced from the two previous measurements, knowing the specific mass of the alloy which has been measured by the Archimedes method by immersion in butyl phthalate maintained at 30 ° C (+ 0.1 ° C ).
• table 9 contains, for comparison, the values relating to some materials of the prior art (samples 5 to 13), some of which are known as thermal barrier (samples 5 to 8 ).
• the thermal conductivity of the quasicrystalline alloys constituting the protective elements of the present invention is considerably lower than that of metallic materials (aluminum metal or quadratic Al 2 Cu), given by way of comparison. It is two orders of magnitude less than that of aluminum and an order of magnitude to that of stainless steel usually considered as a good thermal insulator. In addition, it is lower than that of alumina and quite comparable to that of zirconia doped with Y 2 ° 3 'considered as the archetype of thermal insulators in 1'industrie.
• the thermal diffusivity of the alloys 90, 100, 110, 120 and 130 was determined. These alloys, which form defined aluminum compounds, have compositions close to those of the quasi-crystalline alloys which can be used for the protective elements of the present invention. However, they do not have the quasi-crystalline structure defined above. In all cases, their thermal diffusivity is greater than 5.10 " 6 m 2 / s, that is to say much greater than that of the alloys selected for the present invention.
• the measurement of the thermal diffusivity was carried out according to the method of Example 11.
• Each test tube was placed under a stream of purified argon in the center of an oven heated by the Joule effect; the temperature rise rate, programmed by computer, varied linearly at the rate of 5 ° C / min.
• All the samples according to the present invention show an approximately linear increase in o. with temperature.
• the value of o; determined at 700 ° C is close to twice that measured at room temperature.
• the specific heat increases with temperature and reaches from 800 to 900 J / kgK at 700 ° C.
• the specific mass decreases on the order of 1 to 2% as indicated by thermal expansion or neutron diffraction measurements.
• Figures 1, 2 and 3 respectively represent the evolution of a as a function of the temperature for the alloys 28, 31 and 33. The measurements recorded during heating are represented by black squares, those recorded during cooling by white squares.
• the variation in the thermal expansion of the alloy 2 was measured.
• the thermal expansion curve is app 'araître that the coefficient of expansion depends very little on the tempera- ture and is 9.10 -6 / ° C, the value close to that of stainless steels.
• Example 14 The superplastic behavior of certain alloys likely to constitute the thermal protection elements of the present invention was studied. Cylindrical test pieces 4 mm in diameter and 10 mm in length, with strictly parallel faces, were produced according to the same method as those of Example 1 with alloys 34 and 35. These test pieces were subjected mechanical compression tests on an INSTROM machine. Tests were carried out up to a load of 250 MPa, at a speed of movement of the beam of 50 ⁇ m / min, the temperature being kept constant between 600 and 850 ° C. The two alloys exhibit a superplastic behavior from 600 "C.
• Example 15 The superplastic behavior of certain alloys likely to constitute the thermal protection elements of the present invention was studied. Cylindrical test pieces 4 mm in diameter and 10 mm in length, with strictly parallel faces, were produced according to the same method as those of Example 1 with alloys 34 and 35. These test pieces were subjected mechanical compression tests on an INSTROM machine. Tests were carried out up to a load of 250 MPa, at a speed of movement of the beam
• a first series of test pieces has been produced.
• the substrate was a massive copper cylinder having a diameter of 30 mm and a height of 80 mm and the coating was applied with a plasma torch according to a conventional technique.
• the C0 test tube is the uncoated copper cylinder.
• the specimen Cl was coated over its entire surface with a layer of 1 mm thick of the alloy 2 and the specimen C2 was coated with a layer of 2 mm thick of the alloy 2.
• the C5 test tube comprises a layer of alloy 2 constituting the thermal protection element of the present invention serving as a bonding layer and a layer of yttria zirconia.
• the C3 and C4 test pieces used for comparison respectively comprise a layer of yttria-containing zirconia and a layer of alumina.
• test pieces A0 to A2 Another series of test pieces was produced with, as support, a stainless steel tube having a length of 50 cm, a diameter of 40 mm, a wall thickness of 1 mm (test pieces A0 to A2).
• the support tube is coated at one of its ends over a length of 30 cm.
• the deposits were made with an oxy-gas torch. Table 10 below gives the nature and thickness of the layers for the different test pieces. The precision on the final thicknesses of the deposits was + 0.3 mm. All the test pieces were fitted with very low inertia Chromel - Alumel thermocouples.
• FIG. 4 represents a test tube of the copper cylinder 1 type comprising a coating 2 and provided with a central thermocouple 3 and a lateral thermo ⁇ couple 4, both being inserted up to half the length of the cylinder .
• FIG. 5 represents a hollow tube 5 in which a flow of hot air 6 is passed and which is provided with three thermocouples designated respectively by TI, T2 and T3, the first two being inside the tube and placed respectively at beginning of the coated area and at the end of the coated area, and the third being on the outer surface of the coating.
• test pieces C0, Cl, C2, C3, C4 and C5 were placed on their base on a refractory brick. Successive heat pulses lasting 10 s were applied to each specimen at 60 s intervals and the response of the thermocouples was recorded. These pulses were produced by the flame of a torch, placed at a constant distance from the specimen and oriented opposite the thermocouple close to the surface. The flow of combustion gases was carefully controlled and kept constant throughout the experiment. Two series of experiments were carried out: one with tests vettes initially at 20 ° C and the other with test tubes initially at 650 ° C.
• the CO to C5 test tubes make it possible to define three parameters which summarize the results of the experiment, namely the maximum temperature difference P between the two thermo ⁇ couples, ⁇ T / ⁇ t the rate of temperature rise of the lateral thermo ⁇ couple 4 during the pulse and the temperature increment ⁇ T produced in the center of the test tube (thermocouple 3). These data are shown in Table 10. It was found that the zirconia layer of the C3 specimen did not resist more than three pulses and was cracked from the first pulse. The C2 sample did not start to crack until the sixth pulse and the C1 sample withstood more than 50 pulses. These results show that the protective elements of the present invention, used as a thermal barrier, have performances at least equivalent to those of zirconia.
• Example 17 Use of the protective elements according to the invention as a thermal barrier underlay.
• the thermal protection element of the present invention constitutes an undercoat. It was found that the zirconia layer of the C3 specimen did not resist more than three heat pulses and was cracked from the first pulse.
• the surface temperature of the zirconia deposit measured by a third thermocouple placed in contact with the deposit at the end of the tests, stabilized at 1200 ° C. .
• the thermal protection elements of the present invention are therefore well suited to the production of bonding sub-layers, in particular for thermal barriers.
• EXAMPLE 18 Application of a thermal protection element of the present invention to the insulation of a reactor.
• Test specimens A0, A1 and A2 were used to assess the ability of the alloys of the invention to thermally insulate a device.
• the test pieces were each provided with 3 thermocouples TI, T2 and T3 as shown in FIG. 5.
• a current of hot air at constant flow rate was sent through the stainless steel tube constituting the substrate of each test piece.
• the inlet air temperature, measured using the TI thermocouple was 300 + 2 "C.
• the surface temperature, measured using the T3 thermocouple was recorded as a function of the time from the start of the hot air generator
• the thermocouple T2 made it possible to verify that the transient conditions for establishing the hot air flow were identical for all the measurements.
• Figures 6 and 7 show the evolution of the surface temperature of each of the test pieces A0, Al and A2 as a function of time.
• the surface temperature of the AO specimen (without coating) exceeds at equilibrium that of the A2 specimen by 3
• thermal protection elements of the present invention give interesting results with regard to thermal insulation.

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• 1991
  • 1991-01-18 FR FR9100549A patent/FR2671808B1/fr not_active Expired - Fee Related
• 1992
  • 1992-01-15 AU AU12717/92A patent/AU648876B2/en not_active Expired
  • 1992-01-15 ES ES92904842T patent/ES2110492T3/es not_active Expired - Lifetime
  • 1992-01-15 WO PCT/FR1992/000030 patent/WO1992013111A1/fr active IP Right Grant
  • 1992-01-15 DE DE69223180T patent/DE69223180T2/de not_active Expired - Lifetime
  • 1992-01-15 JP JP50500192A patent/JP3244178B2/ja not_active Expired - Lifetime
  • 1992-01-15 EP EP92904842A patent/EP0521138B1/fr not_active Expired - Lifetime

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