Tungsten-diamond composite and its manufacturing process

Abstract

The present invention relates to tungsten-diamond composite materials and their manufacturing processes. The invention also relates to the use of such materials for manufacturing parts intended for high-temperature applications such as aviation, aerospace, and nuclear energy. Parts intended for aviation, aerospace, and nuclear energy applications, comprising a material according to the invention, constitute another object of the invention. Figure for the abstract: None

Description

Title of the invention: Tungsten-diamond composite and its manufacturing process Technical field of the invention

[0001] The present invention relates to tungsten-diamond composite materials (tungsten-diamond) and their manufacturing processes.

[0002] The invention also relates to the use of such materials for the manufacture of parts intended for high heat fluxes in fields such as aviation, aerospace and nuclear energy.

[0003] Parts intended for the fields of aviation, aerospace and nuclear energy, comprising a material according to the invention, constitute another object of the invention.

[0004] These parts can, for example, be or form part of the internal lining of a rocket engine, an aircraft engine or a nuclear fusion or fission reactor. Technical background

[0005] Materials used in aerospace applications are subjected to extreme environmental conditions. They are exposed to extreme temperatures, high heat fluxes, and must be able to withstand and absorb high-intensity shocks and vibrations.

[0006] Tokamaks, like rocket engines, use carbon (particularly carbon fibers or graphite) or tungsten as materials under high heat flux. Carbon has the disadvantage of eroding rapidly, which is not the case with tungsten.

[0007] Indeed, tungsten is a refractory material with low reactivity and is widely used in high-temperature fields such as aviation, aerospace, and nuclear energy. However, tungsten degrades rapidly under thermal shock due to its modest thermal conductivity (<100 Wm⁻².K⁻¹).

[0008] There is therefore a real need for a material combining a low level of erosion with good thermal conductivity (>400 Wm⁻².K⁻¹) under high continuous (~0.1 - 100 MW.m²) and transient (>20 MW.m².s⁻¹) power density. Summary of the invention

[0009] The present invention is specifically designed to meet these needs by providing a composite material comprising tungsten and diamond (tungsten-diamond), characterized in that it comprises a diamond substrate having a thickness of 0.1 to 1 mm, a density greater than 99%, and which can be either of a purity greater than 99.95%, i.e., doped with boron at an atomic percentage of 0.05 to 0.5%, said diamond substrate being coated

[0010] - on one of its faces, a layer of molybdenum with a density greater than 99% exhibiting a thickness of 1 to 100 pm (Mo-1 layer),

[0011] - possibly, on the other face located opposite the Mo-1 layer, of a molybdenum layer with a density greater than 99% and a thickness of 0.5 to 5 pm (Mo-2 layer),

[0012] - of a tungsten layer with a density greater than 99% and a thickness of 10 to 100 pm, on • the uncoated face of the substrate, located opposite the Mo-1 layer, or • the side of the substrate containing the Mo-2 layer, located opposite the Mo-1 layer.

[0013] The densities of molybdenum, tungsten, or diamond can be measured by scanning electron microscopy with image processing of a slice of a sample after cutting, or also by weighing. For example, in the case of a cut sample, the percentage of porous areas is measured on the image of the slice, and the density in % is 100 minus the porosity.

[0014] Porosity is a physical quantity defined as the ratio between the volume of voids and the total volume of a material (i.e. the sum of the volume of solid and the volume of pores), its value being between 0 and 1 (or, as a percentage, between 0 and 100%).

[0015] The materials according to the invention combine a low level of erosion thanks to the tungsten layer with good thermal conductivity (>400 Wm*.K*) thanks to the diamond substrate under high continuous power density (~0.1 - 100 MW.m2) and transient (>20 MW.m2.s05).

[0016] The invention also relates to the manufacturing processes of these materials as detailed below.

[0017] The invention also relates to the use of such materials for the manufacture of parts intended for high heat fluxes in fields such as aviation, aerospace and nuclear energy.

[0018] Parts intended for the fields of aviation, aerospace and nuclear energy, comprising a material according to the invention, constitute another object of the invention.

[0019] These parts can, for example, be or form part of the internal lining of a rocket engine, an aircraft engine or a nuclear fusion or fission reactor. Brief description of the figures

[0020] Other features and advantages of the invention will become apparent upon reading the detailed description that follows, for an understanding of which reference should be made to the attached figure in which:

[0021] [Fig. 1] represents an embodiment in which the tungsten-diamond composite material according to the invention comprises an intermediate layer of molybdenum (Mo-2) deposited by physical vapor deposition (PVD).

[0022] [Fig.2] represents an embodiment in which the composite material tungsten-diamond is made by physical vapor deposition (PVD) of tungsten directly onto diamond without an intermediate layer of molybdenum (Mo-2).

[0023] Detailed description of the invention The present invention relates to a tungsten-diamond composite material, characterized in that it comprises a diamond substrate having a thickness of 0.1 to 1 mm, a density greater than 99%, and which may be either of a purity greater than 99.95% or doped with boron at an atomic percentage of 0.05 to 0.5%, said diamond substrate being coated

[0024] - on one of its faces, a layer of molybdenum with a density greater than 99% exhibiting a thickness of 1 to 100 pm (Mo-1 layer),

[0025] - possibly, on the other face located opposite the Mo-1 layer, of a molybdenum layer with a density greater than 99% and a thickness of 0.5 to 5 pm (Mo-2 layer),

[0026] - of a tungsten layer with a density greater than 99% and a thickness of 10 at 100 pm, on • the uncoated face of the substrate, located opposite the Mo-1 layer, or • the side of the substrate containing the Mo-2 layer, located opposite the Mo-1 layer.

[0027] It should be noted that for diamond, purity and density are important parameters. Boron doping makes the diamond conductive in order to avoid problems of electric arcing when exposed to plasma.

[0028] The presence of the tungsten layer on the surface of the diamond substrate protects the diamond from erosion and the excellent thermal conductivity of the diamond allows good heat diffusion during thermal shocks.

[0029] Furthermore, the inventors have observed that the presence of the intermediate Mo-2 layer between the tungsten and the diamond and, where applicable, Mo-1 between a metallic attachment surface and the diamond improves the mechanical and thermal junction between the diamond, the tungsten and, where applicable, a metallic attachment surface, effectively improving the performance of the composite material under high continuous and / or transient power density of a part intended for the fields of aviation, aerospace and nuclear energy.

[0030] Power density refers to the power that passes through a surface during heat transfer, that is, the thermal energy transferred per unit of time and area. It is expressed in watts per square meter.

[0031] In the context of the invention, density means the percentage of the material's volume that is not empty. In practice, it is measured by scanning electron microscopy with image processing of a cross-section of a sample after cutting, or also by weighing.

[0032] The diamond substrate, with a purity greater than 99.95% or doped with boron at an atomic percentage of 0.05 to 0.5%, may be monocrystalline or polycrystalline, has a density greater than 99%, and a thermal conductivity >1000 W / m·K at 20°C. It can be produced by chemical vapor deposition (CVD), a technique that allows for precise control of the impurity level in the crystals by controlling the purity of the gas phase. This method is well known to those skilled in the art.

[0033] One can also use one of the variants of CVD known to the person skilled in the art such as, for example, plasma-assisted processes such as MPCVD (or Microwave plasma-assisted in English); PECVD (or Plasma Enhanced CVD in English); RPECVD (or Remote plasma-enhanced in English); ALCVD (or Atomic layer CVD in English); HWCVD (or Hot wire CVD in English); or MOCVD (from the English Metalorganic Chemical vapor deposition).

[0034] The diamond substrate can be a plate or a surface of any geometry.

[0035] Tungsten and molybdenum can be pure or in the form of alloys. Preferably, these metals are pure with a purity greater than 99.9% and a density greater than 99%.

[0036] Another object of the invention is a method for manufacturing a composite material comprising tungsten and diamond (tungsten-diamond) as described above, comprising the following steps:

[0037] A) a diamond substrate of greater than 99.95% purity or doped with boron at an atomic percentage of 0.05 to 0.5% is available, which can be monocrystalline or polycrystalline, which has a density greater than 99% and a thermal conductivity >1000 Wm*.K1 at 20°C obtained by chemical vapor deposition (CVD), having a thickness of 0.1 to 1 mm,

[0038] B) one face of this substrate is coated with a layer of molybdenum, having a thickness of 1 to 100 pm (Mo-1 layer), by physical vapor deposition (PVD),

[0039] C) Alternatively to A) and B) the diamond substrate can also be grown by chemical vapor deposition (CVD) to a thickness of 1 to 100 pm molybdenum (Mo-1 layer) which will have been obtained beforehand by physical vapor deposition (PVD) or by any other method,

[0040] D) Optionally, the other face of the diamond substrate obtained in B) or C), located opposite the Mo-1 layer, is coated with a molybdenum layer, having a thickness of 0.5 to 5 pm (Mo-2 layer), by physical vapor deposition (PVD),

[0041] E) the • the uncoated face of the diamond substrate obtained in step B) or C), located opposite the Mo-1 layer, or • the face of the diamond substrate containing the Mo-2 layer obtained in step D), located opposite the Mo-1 layer,

[0042] of a tungsten layer having a thickness ranging from 10 to 100 pm, by physical vapor deposition (PVD).

[0043] In the materials of the invention, tungsten and molybdenum are deposited on the diamond substrate by the physical vapor deposition (PVD) method.

[0044] Physical vapor deposition can be carried out by all methods known to those skilled in the art, in particular

[0045] - vacuum evaporation,

[0046] - evaporation by electron beam in the vapor phase (or electron beam evaporation (in English),

[0047] - cathodic sputtering (or sputtering in English) where the metal particles are separated from their substrate by ion bombardment,

[0048] - pulsed laser ablation (or pulsed laser deposition or pulsed laser ablation in English) where atoms and ions are vaporized under the action of intense laser radiation,

[0049] - molecular jet epitaxy, and

[0050] - electric arc deposition (or Arc PVD in English) where atoms and ions are vaporized under the action of a strong current, caused by electrical discharge between two electrodes presenting a strong potential difference, which detaches metal particles and causes them to pass into the gaseous phase.

[0051] Preferably, the tungsten layer and the molybdenum layer(s) are deposited by the physical vapor deposition method by sputtering. In this method, an argon plasma (typically) sputters a tungsten or molybdenum target, and the ejected atoms are deposited onto the surface to be coated.

[0052] The invention relates to the use of a material according to the invention, for the manufacture of parts intended for the fields of aviation, aerospace and nuclear energy.

[0053] Another object of the invention relates to parts intended for the fields of aviation, aerospace and nuclear energy, comprising a material according to the invention.

[0054] EXAMPLE: Preparation of a composite material comprising tungsten, molybdenum and diamond according to the invention

[0055] The various materials in solid or gaseous form used in the process of the invention and in the examples are, in general, commercial compounds or can be prepared by any process known to those skilled in the art. All metals used have a minimum purity of 99.9%. The CVD filament furnace for manufacturing diamond substrates and the PVD cavity for all metal deposits are commercial technologies accessible to those skilled in the art. Implementation#:

[0056] A polycrystalline diamond substrate, with a purity greater than 99.95%, a density greater than 99%, a thickness of 0.5 mm, and a rectangular surface area of ​​20 x 30 mm, is produced by the CVD method in a hot filament furnace. This substrate is grown at ~800–900°C on a 50 µm thick molybdenum film with a density greater than 99% in a reduced-pressure atmosphere (~0.1 bar) of hydrogen and methane heated by filaments at ~2000°C. This substrate is then coated by the PVD (powder deposition of the target material with an argon plasma) method with a 2 µm thick layer of molybdenum with a density greater than 99% on the face opposite the 50 µm molybdenum-coated face. The 2 pm layer of Mo is then covered with a 10 pm layer of tungsten with a density greater than 99%, again using the PVD method.

Claims

Demands

1. A tungsten-diamond composite material, characterized in that it comprises a diamond substrate having a thickness of 0.1 to 1 mm, a density greater than 99%, and which may be either of a purity greater than 99.95% or doped with boron at an atomic percentage of 0.05 to 0.5%, said diamond substrate being coated - on one of its faces, with a molybdenum layer of density greater than 99% having a thickness of 1 to 100 pm (Mo-1 layer), - optionally, on the other face opposite the Mo-1 layer, with a molybdenum layer of density greater than 99% having a thickness of 0.5 to 5 pm (Mo-2 layer), - with a tungsten layer of density greater than 99% having a thickness of 10 to 100 pm, on • the uncoated face of the substrate, located opposite the Mo-1 layer, or • the face of the substrate containing the Mo-2 layer, located opposite the Mo-1 layer.

2. A method for manufacturing a composite material comprising tungsten and diamond (tungsten-diamond) according to claim 1, characterized in that it comprises the following steps: A) a diamond substrate of a purity greater than 99.95% or doped with boron at an atomic percentage of 0.05 to 0.5% is available, which may be mono- or polycrystalline, which has a density greater than 99% and a thermal conductivity >1000 Wm*.K1 at 20°C obtained by chemical vapor deposition (CVD), with a thickness of 0.1 to 5 mm, B) one face of this substrate is coated with a layer of molybdenum, with a thickness of 1 to 100 pm (Mo-1 layer), by physical vapor deposition (PVD), C) alternatively to A) and B) the diamond substrate can also be grown by chemical vapor deposition (CVD) with a thickness of 1 to 100 pm of molybdenum (Mo-1 layer) which will have been obtained beforehand by physical vapor deposition (PVD) or by any other method.

3.

4. D) Optionally, the other face of the substrate obtained in B) or C), located opposite the Mo-1 layer, is coated with a molybdenum layer, 0.5 to 5 pm thick (Mo-2 layer), by physical vapor deposition (PVD). E) The coating • the uncoated face of the substrate obtained in step B) or C), located opposite the Mo-1 layer, or • the face of the substrate containing the Mo-2 layer obtained in step D), located opposite the Mo-1 layer, of a tungsten layer with a thickness ranging from 10 to 100 pm, by physical vapor deposition (PVD). Use of a material according to claim 1, for the manufacture of parts intended for the fields of aviation, aerospace and nuclear energy. Parts intended for the fields of aviation, aerospace and nuclear energy, characterized in that they comprise a material according to claim 1.

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