Measuring temperature of metallic part under uniaxial deformation pressure by optical pyrometry

Abstract

A method for preparing a metal part pressurized under isentropic, shock-type or compression-type, uniaxial deformation conditions, so as to measure the temperature of same by optical pyrometry. The method includes forming an emissive coating on a face of the metal part, having a thickness of 250 to 550 nm, and fixing an anvil-shaped window on the emissive coating. The emissive coating includes a first and a second layer of amorphous carbon, the first layer being inserted between the face of the metal part and the second layer, and having a carbon hybridization rate sp.sup.3 greater than the carbon hybridization rate sp.sup.3 of the second layer. A method for measuring, by optical pyrometry, the temperature of a metal part pressurized under isentropic, shock-type or compression-type, uniaxial deformation conditions.

Claims

1. A method for preparing a metal part so as to measure a temperature of the metal part by optical pyrometry when the metal part is put under pressure under uniaxial deformation conditions of a shock type or of an isentropic compression type, the method comprising: forming an emissive coating on one face of the metal part; and fixing, on the emissive coating, an anvil window, wherein the emissive coating has a thickness of between 250 nm and 550 nm and comprises a first layer of amorphous carbon and a second layer of amorphous carbon, the first layer being interposed between the face of the metal part and the second layer, and having a degree of carbon hybridisation sp.sup.3 greater than a degree of carbon hybridisation sp.sup.3 of the second layer.

2. The method according to claim 1, wherein the first layer has a thickness of between 50 and 150 nm and the second layer has a thickness of between 200 and 40 nm.

3. The method according to claim 2, wherein the emissive coating consists solely of the first and second layers of amorphous carbon.

4. The method according to claim 1, wherein the first and second layers have an atomic hydrogen content of less than 20%.

5. The method according to claim 1, further comprising: polishing the face of the metal part until a surface roughness of the face of 10 to 30 nm is obtained, wherein the polishing is carried out before formation of the emissive coating.

6. The method according to claim 1, wherein formation of the emissive coating comprises formation of the first layer on the face of the part by radio-frequency cathodic sputtering of a carbon target.

7. The method according to claim 1, wherein formation of the emissive coating comprises formation of the second layer on the first layer by physical vapour deposition by bombardment of a graphite target by electron beam.

8. A method for measuring, by optical pyrometry, a temperature of a metal part put under pressure under uniaxial deformation conditions of a shock or isentropic compression type, the measurement method comprising: preparing the metal part by implementing a preparation method according to claim 1; applying to the metal part, a pressure under uniaxial deformation conditions of a shock or isentropic compression type; measuring an intensity of an infrared radiation emitted by the emissive coating; and converting the intensity thus measured into a value of the temperature of the metal part put under pressure.

Description

BRIEF DESCRIPTION OF THE FIGURE

(1) The single FIGURE shows a schematic view in longitudinal section of the architecture of the assembly formed by the metal part, the multilayer coating and the anvil window element according to a possible embodiment of the invention. The arrow illustrates the direction of propagation of the putting of the part under pressure under uniaxial deformation conditions.

DETAILED DISCLOSURE OF PARTICULAR EMBODIMENTS

(2) In order to illustrate the preparation method that is the subject matter of the invention, we shall now describe an example of preparation of a metal part according to the invention.

(3) The metal part that we are going to use in this example is a copper disc, having a diameter of 40 mm and a thickness of 4 mm.

(4) It is preferable to carry out a polishing of the surface of the metal part intended to receive the multilayer coating, so as to obtain a mean roughness of between 10 and 30 mm. This polishing facilitates the attachment of the multilayer coating, it also makes it possible to avoid the presence of any surface roughness that may be the site of creation of hot spots, in the case of experiments under shock, disturbing the measurements of the temperature of the part.

(5) The polishing may for example be carried out using a rotary polisher equipped successively with abrasive discs having a finer and finer roughness, and with felt discs on which diamond suspensions are sprayed in order to carry out a finishing polishing.

(6) We have presented in the following table the range of abrasive discs and felt discs that we use, as well as their use parameters.

(7) TABLE-US-00001 Rotation speed of Duration Pressure force abrasive Type of abrasive (minutes) (N) (revolutions/minute) SiC 1200 disc 2 25 220 SiC 2400 disc 2 25 220 SiC 4000 disc 2 25 220 3 m diamond 2 25 220 suspension 3 m diamond 2 20 190 suspension

(8) This polishing is followed by cleaning, for example using a mixture of ethanol and acetone, and then drying of the part, for example by compressed air or compressed inert gas, if there is a concern about obtaining surface oxidation of the part.

(9) Depending on the thickness of the emissive coating that it is wished to obtain and the type of part to be coated, the thicknesses of the first and second amorphous carbon layers will be adapted.

(10) In this exemplary embodiment, a first layer of amorphous carbon is produced with a thickness of 100 nm by radio-frequency cathodic sputtering (RFPVD, standing for radio-frequency physical vapour deposition) of a carbon target. The deposition is carried out in a physical vapour deposition reaction chamber and the deposition parameters are for example: nature of the plasmagenic gas: argon RF power: 75 W working pressure: 1.10.sup.1 mbar carbon target/substrate distance: 2.5 cm duration: 5 minutes

(11) Next, on this first layer, a second amorphous carbon layer with a thickness of 300 nm is produced. This second layer is for example produced by electron beam physical vapour deposition (EBPVD) in the same PVD reaction chamber used for producing the first layer. The deposition parameters are for example: electron gun power: 900 W working pressure: 5.10.sup.5 mbar carbon source/substrate distance: 15 cm duration: 30 minutes

(12) The thickness of the multilayer coating is thus 400 nm.

(13) We carried out a semi-quantitative XPS (X-ray photoelectron spectroscopy) analysis of the first and second layers in order to quantify their degree of hybridisation sp.sup.3. We obtained a 35% degree of hybridisation sp.sup.3 and 65% hybridisation sp.sup.2 for the first layer and a 30% degree of hybridisation sp.sup.3 and 70% hybridisation sp.sup.2 for the second layer.

(14) A layer of glue is next deposited on the multilayer coating and makes it possible to fix a so-called anvil window on the coating.

(15) The layer of glue and the anvil window are chosen so that they are transparent in the range of wavelengths (IR) captured by the optical pyrometer that it is wished to use. This is because the heat flux issuing from the metal part must not to a major extent be absorbed by the layer of glue or by the anvil window, so that the measurement carried out can be used and corresponds to the temperature issuing from the metal part with the coating.

(16) It is possible for example to use a resin resulting from a mixture of Araldite AY 103-1 and Aradur HY 951 at 10% to fix the anvil window on the coating and a lithium fluoride crystal, with a thickness of between 10 and 20 mm, as the anvil window.

(17) In our exemplary embodiment, a 10 m thick layer of resin is deposited on the coating and, within a period of between 5 and 60 seconds, the lithium chloride crystal is disposed on this resin while it is still liquid (before polymerisation thereof): the still liquid adhesive then spreads over the entire common surface between the coating part and the LiF crystal. Next a pressure of 2 kg is applied for a period of between 8 and 12 hours to the crystal, in order to obtain a final thickness of glue of less than 10 micrometers over the whole of the glued surface.

(18) The metal part thus prepared is shown in the single FIGURE: the metal part 1 comprises, on one of its faces 3, a multilayer coating 2 consisting here of a first layer of amorphous carbon 4 and a second layer of amorphous carbon 5, a layer of glue 6 and an element 7 that will serve as an anvil window. In this FIGURE, the direction of the dynamic mechanical force is applied to the bottom face of the metal part 1 and is represented by the arrow.

REFERENCES CITED

(19) [1] Perez M. Residual temperature measurements of shocked copper and iron plates by infrared pyrometry, Shock Waves of Condensed Matter 1991, (1992), p. 737-740. [2] Perez M. Precision infrared pyrometry for post-shock temperature measurements of metal materials in the range 70-1000 C., Journal de Physique IV, Conference C3, supplement to the Journal de Physique III, vol. 1, (1991), pp. 371-378. [3] Chauvin C. et al. An application of the emissive layer technique to temperature measurement by infrared optical pyrometer, Shock Compression of Condensed Matter 2011, AIP Conf. Proc. 1426, (2012), pp. 368-371. [4] Grill A. Diamond-like carbon: state of the art, Diamond and Related Materials, 8 (1999), pages 428-434.