Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N25/00—Investigating or analyzing materials by the use of thermal means
  • G01N25/18—Investigating or analyzing materials by the use of thermal means by investigating thermal conductivity
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
  • B22F10/20—Direct sintering or melting
  • B22F10/28—Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
  • B22F12/90—Means for process control, e.g. cameras or sensors
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y30/00—Apparatus for additive manufacturing; Details thereof or accessories therefor
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y50/00—Data acquisition or data processing for additive manufacturing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy

Definitions

• the present invention relates to the field of manufacturing metal parts by sintering and in-situ and non-destructive inspection and characterization of the parts formed.
• the invention relates to a method and a system for the manufacture of a metal part by laser sintering and in-situ and non-destructive control and characterization of the metal part by modulated photothermal radiometry with synchronous detection.
• the checks carried out are non-destructive, i.e. they do not modify the properties of the part checked.
• the usual non-destructive tests are radiology, ultrasonic testing and modulated thermal photo radiometry.
• photothermal radiometry methods make it possible to characterize and control the homogeneity and the physical and thermal properties of a metallic part in a non-destructive way from the analysis of the thermal waves emitted by the part when heated.
• four different methods can be distinguished, listed and described below:
• the pulse method consists of heating the part to be characterized using a single pulse from a heat source, for example a "flash" lamp or a pulsed laser, with known energy parameters.
• a heat source for example a "flash" lamp or a pulsed laser
• this technique relies on a relatively short measurement which consequently limits the accuracy of the data obtained.
• the continuous heating method is based on continuous heating of the surface of the part to be characterized. By measuring the surface temperature and comparing it to the measurements obtained for reference samples, the physical and/or thermal properties of the part are determined. Although more accurate than the pulse method, continuous heating leads to the risk of overheating the part and, consequently, changing its properties.
• Periodic pulsed heating makes it possible to overcome the drawbacks of the two preceding methods.
• the temperature is maintained at a sufficient level for measurements, while reducing the risk of overheating the part.
• each of these three methods requires the knowledge of the emissivity of the part which is generally not known before its complete manufacture. In addition, it is necessary to know the heating flux absorbed by the part and, therefore, the laser power as well as the absorption coefficient of the part. These three methods are therefore not perfectly suited to characterize and control the homogeneity and the physical and/or thermal properties of the part during its manufacture.
• Patent application FR 3007523 Al describes a modulated radiometry method with synchronous detection making it possible to determine the thermal diffusivity of a part that does not require the use of a reference sample and is not dependent on heat losses during heating. of the room.
• the patent application FR 3075377A1 describes a modulated radiometric method with synchronous detection making it possible to characterize and control the homogeneity of metal parts comprising several distinct zones manufactured by sintering.
• the method described in this application does not require prior knowledge of the heating flux absorbed by the part and, therefore, does not require knowledge of the laser power used for heating as well as the absorption coefficient of the part.
• the object of the invention is to meet, at least in part, this need.
• the invention relates to a method for manufacturing a metal part by laser sintering and for in-situ and non-destructive characterization of the metal part, comprising the following steps: (a) formation of at least one layer of the metal part by laser sintering, comprising the emission by a laser device of at least one laser beam onto a powder bed of the material constituting the layer;
• step (b) emission of at least one laser beam by the same laser device having been used for the laser sintering according to step (a), so as to irradiate and thereby heat at least part of the surface of the layer formed, in order to carry out its characterization by modulated photothermal radiometry with synchronous detection.
• step (a) and step (b) allows the method according to the invention to be quick and simple to implement because it is freed from the need for a source additional laser.
• the power of the laser beam is continuous, preferably greater than 100 W, and/or the laser beam is focused on the powder bed.
• the laser beam has a wavelength between 0.2 ⁇ m and 1.5 ⁇ m.
• step (b) comprises power modulation at a given frequency and defocusing of the laser beam towards the formed layer.
• the defocusing of the laser beam advantageously makes it possible to reduce the irradiance of the laser beam on the surface of the layer and to increase the size of the irradiated surface.
• defocusing is meant here diverging the rays of the laser beam so that the latter is not focused on the irradiated surface.
• the irradiance of the laser beam on the irradiated surface is lower than the irradiance corresponding to the melting threshold of the layer, preferably lower than 10 10 W/m 2 .
• the laser beam is modulated sinusoidally in power.
• the modulation frequency of the laser beam is between 0.01 Hz and 10 kHz, preferably between 0.1 Hz and 1 kHz.
• the laser beam has a wavelength between 0.2 ⁇ m and 1.5 ⁇ m.
• the radius ro of the defocused beam on the surface irradiated at 1/e in intensity is greater than 100 ⁇ m.
• the power of the laser beam is adjusted so that the temperature of the part of the layer heated by irradiation is lower than the melting threshold temperature of the layer.
• a radius of a laser beam at 1/e in intensity we mean here the radial distance between the center of the laser beam, that is to say the point where the light intensity is maximum, and the point where the The luminous intensity is equal to 1/th times the maximum intensity, e being the Euler number.
• the axis normal to the irradiated surface and the laser beam form an angle of incidence comprised between 5° and 60°.
• Such an angle of incidence advantageously makes it possible to limit the reflections of the laser beam by the irradiated surface towards the laser device.
• the method comprises, after step (b), the following steps:
• step (d) acquisition of the Atp phase difference between the laser beam emitted during step (b) and the heat flux at at least one point of the irradiated surface, so as to obtain the characterization of the layer.
• step (d) the phase shift Atp is acquired at a plurality of points on the irradiated surface so as to obtain a map of the phase shifts of the irradiated surface.
• mapping of phase shifts is meant here a two-dimensional image spatially representing the phase shifts Atp at a plurality of points on the irradiated surface.
• step (d) the Atp phase shift can be acquired by comparison with the results obtained for reference samples whose phase shifts between the heat flux and a laser beam identical to that of step (b) are known.
• the method comprises the following steps:
• step (f) acquisition, from the minimum phase shift and/or the minimum phase shift frequency, of the thickness L and/or the thermal conductivity and/or the heat capacity and/or the thermal diffusivity D of the layer and/or the thermal resistance of the layer/substrate interface at the level of the at least one point or at the level of each of the points.
• the thickness L and/or the thermal diffusivity D of the layer is or are calculated from the following formulas:
• ro is the radius of the laser beam on the surface irradiated at 1/e in intensity
• ⁇ f represent known coefficients which depend on the ratio ro/L [2], the formulas being applied to the center of the laser beam. As shown in [2], ro must be between 2L and 100L.
• step (f) the acquisition is carried out by comparison with phase shifts obtained for reference samples whose physical and thermal properties are known.
• steps (a) and (b), preferably steps (a) to (d), preferably steps (a) to (f), can be repeated so as to manufacture the metal part comprising a structure multilayer, of which at least some of the layers have been characterized and/or checked.
• the invention also relates to a system for the manufacture of a metal part by laser sintering and for the in-situ and non-destructive inspection and characterization of the metal part, comprising:
• a laser device comprising a laser source, the laser device being configured to emit, in a first configuration, a laser beam, directed towards the support and adapted to form at least one layer by sintering of the powder, and, in a second configuration , a laser beam, modulated in power at a given frequency and towards the optical system(s) which defocus(es) the beam towards the formed layer so as to irradiate and thereby heat at least part of the surface of the formed layer.
• the system is configured so that the irradiance of the laser beam on the layer, in the second configuration, is lower than the melting threshold of the lower layer, preferably lower than 10 10 W/m 2 .
• the laser device is configured to, in the first configuration, emit a laser beam at a continuous power greater than 100 W, and/or, in the second configuration, emit a modulated laser beam, preferably sinusoidally, in power at a frequency between 0.01 Hz and 10 kHz, preferably between 0.1 Hz and 1 kHz.
• each of the laser beams has a wavelength of between 0.2 ⁇ m and 1.5 ⁇ m.
• the system comprises a plurality of optical systems, each optical system being configured so that it receives a power modulated laser beam emitted by the laser device in the second configuration, it defocuses said laser beam towards the layer formed so as to irradiate and thereby heat at least a part of the surface of the layer formed, the part of the irradiated surface being different from each of the other parts of the irradiated surface if the optical systems other than that which receives the beam, defocus the laser beam.
• An irradiated surface part differs from another irradiated surface part in that their radii differ and/or their centers differ.
• the laser device is configured to emit, in the second configuration, the modulated laser beam towards each of the optical systems individually, that is to say towards only one at a time.
• the optical system(s) is (are) configured to direct the defocused laser beam onto the layer with a radius ro of the defocused beam onto the irradiated surface at 1/e in intensity greater than at 100 p.m.
• the optical system(s) is (are) arranged outside the passage zone of the laser beam.
• the optical system(s) is (are) arranged outside the zone corresponding to the passage of the laser beam in the first configuration. This facilitates the use of the system(s), in particular, it is not necessary to move the optical system(s) by relative to the laser device to switch from the first configuration to the second configuration and vice versa.
• the optical system(s) can be immobile with respect to the laser device.
• the laser device further comprises:
• a deflection head configured to, in the first configuration, focus the laser beam on the powder bed and, in the second configuration, direct the laser beam towards the optical system(s).
• the adjustment of the power of the laser source by the optical system advantageously allows the temperature of the part of the layer heated by irradiation to remain below the melting threshold temperature of the layer.
• the electronic system is configured to modulate, preferably sinusoidally, the laser source power according to a plurality of different frequencies between 0.01 Hz and 10 kHz, preferably between 0.1 Hz and 1 kHz.
• the system further comprises:
• thermal detector adapted to measure in real time a heat flux emitted by the layer formed
• an electronic module configured to acquire the phase shift between the defocused laser beam and the heat flux at at least one point on the irradiated surface of the layer.
• the electronic module is configured to acquire the phase shift between the laser beam and the heat flux at a plurality of points on the irradiated surface and to form a map of the phase shifts of the irradiated surface.
• the electronic module can then form a homogeneity map of the layer formed.
• the electronic module is configured to determine the minimum phase shift Acpmin between the laser beam and the heat flux, at the at least one point or at each of the points, and the associated frequency fmin, called minimum phase shift frequency, and to acquire the thickness L and/or the thermal conductivity and/or the thermal capacity and/or the thermal diffusivity D of the layer and/or the thermal resistance of the layer/substrate interface at the level of at least one point or at the level of each of the points.
• the acquisition of the thickness L and/or the thermal conductivity and/or the thermal diffusivity D of the layer and/or the thermal resistance of the layer/substrate interface is made in each of the zones suspected of defects by homogeneity mapping.
• the thermal detector is an infrared camera configured to measure infrared radiation with wavelengths between 1.5 ⁇ m and 11.5 ⁇ m.
• the system includes a magnifying optical system configured to obtain a magnified or reduced image of the thermal flux by the infrared camera.
• the magnification optical system comprises a filter opaque to the radiation emitted by the laser device, preferably to radiation of wavelength less than 1.5 ⁇ m, and transparent to radiation of wavelengths corresponding to the range detectable by the thermal detector, preferably at wavelengths between 1.5 ⁇ m and 11.5 ⁇ m.
• the magnification or reduction factor of the image obtained through the magnification optical system is equal to or less than or greater than 1.
• the part of the support intended to support the powder bed extends along a longitudinal plane, the support being mounted to move relative to the laser device, to the optical system(s) and, where appropriate, to the thermal detector, along said longitudinal plane.
• the support is arranged so that the straight line followed by the laser beam during the sintering of the powder is normal to the longitudinal plane.
• the invention also relates to a use of a system as described above for the implementation of a method as described above.
• Figure 1 is a schematic view of a system according to the invention according to its first configuration.
• Figure 2 is a schematic view of a system according to the invention according to its second configuration.
• Figure 3 A is a top view of a metal part formed by sintering and comprising zones of sub-surface defects.
• Figure 3B is a cross-sectional view of the metal part of Figure 3A.
• Figure 3C is a map of the phase shifts obtained from the method according to the invention and representing part of the metal part of Figures 3A and 3B.
• FIGS. 1 and 2 the various light beams are illustrated by arrowed lines, schematically representing the paths followed by these light beams without illustrating the widths of said beams.
• FIG. 1 There is illustrated in Figure 1 a system 1 according to the present invention, the system 1 being in its first configuration.
• System 1 comprises a support 2, a laser device 3, an optical system 4, an electronic module 5 and a thermal detector 6.
• a bed of powder P is deposited on the support 2.
• the powder is composed of a constituent material of the metal part to be formed.
• the laser device 3 comprises an electronic system 31, a laser source 32 and a deflection and focusing head 33.
• the electronic system 31 controls the power of the laser source 32.
• the deflection head 33 can be a galvanometric head, for example a galvanometric head from SCANLAB.
• the electronic module 5 transmits an instruction 7 to the deflection head 33 so that the latter is configured according to the first configuration.
• the electronic module 5 then transmits an instruction 8 so that the electronic system 31 controls the power of the laser source 32 which then emits a laser beam 9a of continuous power and greater than 100 W, for example 100 W.
• the power control of the source laser 32 is illustrated by the arrow 10.
• the laser beam 9a is transmitted to the head of deflection 33 which then directs the laser beam 9b focused on the bed of powder P.
• the laser beam 9b then heats the powder P, which makes it possible to form a layer C by sintering the powder P.
• the optical system 4 is arranged outside the passage zone of the laser beam 9b.
• the support 2 is movable relative to the deflection head 33 at least along the longitudinal plane in which the powder bed P extends.
• the electronic module 5 can then control the movement of the support 2 by instructions 11, so as to achieve a desired shape and/or thickness for the layer C.
• the laser device 3 After formation of the layer C, under the order of the electronic module 5, the laser device 3 directs the emission of the laser beam 9b towards the optical device 4.
• the electronic module 5 transmits an instruction 12 to the deflection head 33.
• the electronic module 5 then transmits an instruction 13 commanding the electronic system 31 to modulate, preferably sinusoidally, the power of the laser source 32, at a given frequency f between 0.01 Hz and 10 kHz, preferably between 0.1 Hz and 1kHz.
• the laser source 32 then emits a laser beam 14a modulated sinusoidally in power at the frequency f.
• the laser beam 14a has a wavelength of between 0.2 ⁇ m and 1.5 ⁇ m.
• the laser power can be adjusted by the electronic system 31.
• the laser beam 14a is transmitted to the deflection head 33 which then directs it to the optical system 4.
• the optical system 4 then defocuses the laser beam 14b towards the layer C.
• the laser beam 14c irradiates and thereby heats all or at least part of the surface of the layer C.
• the irradiance of the defocused laser beam 14c on the irradiated surface of layer 3 is lower than the melting threshold of the layer, preferably lower than 10 10 W/m 2 .
• a thermal flux 15 is emitted by the heating of the layer C. This thermal flux 15 is then picked up by the thermal detector 6.
• the thermal detector 6 is preferably an infrared camera, for example a “Fast-M2K Rapid IR Camera” from the company Telops. The useful spectral range of infrared camera 6 extends from 1.5 ⁇ m to 5.4 ⁇ m.
• System 1 comprises a magnifying optical system 16 arranged between layer C and thermal detector 6.
• This magnification optical system 16 preferably comprises a lens for magnifying or reducing the image of the irradiated surface of the layer C acquired by the infrared camera 6 by a magnification factor greater than or less than or equal to 1, for example equal at 2 or 0.5.
• a magnification factor equal to 1 corresponds to the absence of the optical system 16.
• This magnification optical system 16 also comprises a filter opaque to radiation of wavelengths less than 1.5 ⁇ m, for example a germanium filter transmitting only wavelengths between 1.5 ⁇ m and 11.5 ⁇ m . This prevents the scattered light, caused by the reflection of the laser beam 14 on the layer C, from interfering with the detection of the thermal flow 15.
• the infrared camera 6 transmits the image of the thermal flow 15 acquired to the electronic module 5, via a connection 17.
• the connection 17 also allows the electronic module 5 to control the infrared camera 6, for example to switch it on, switch it off and /or modify the acquisition parameters.
• the electronic module 5 can then calculate the phase shift Atp between the laser beam 14c and the heat flux 15 at at least one point of the irradiated surface or at a plurality of points, so as to obtain a map of the phase shifts of the irradiated surface.
• the irradiated surface can be all or only part of the upper surface of the layer C.
• the electronic module 5 controls the displacement of the laser beam 14a-c via the deflection head 33 and the optical system 4 to a new zone. It is also possible to envisage several optical systems 4 of different defocusses, the deflection head 33 being able to direct the laser beam 14a towards each of the optical systems 4. It is then possible to scan the upper surface of the layer C by the laser beam 14c and obtain a map of the phase shifts for the whole of this surface. A plurality of thermal flux images 15 can be acquired in a manner similar to what is described previously, with for each image a different frequency of modulation of the laser beam 14.
• the electronic module 5 can acquire the phase shift Atp between the laser beam 14a and the heat flux 15 at at least one point of the irradiated surface or at a plurality of points, so as to obtain a map of the phase shifts of the irradiated surface.
• the electronic module 5 can then determine the minimum phase shift Acpmin between the laser beam 14 and the heat flux 15 as well as the associated frequency fmin, called minimum phase shift frequency, for each of the points with defects.
• the electronic module 5 can then acquire, from the minimum phase shift Acpmin and/or the minimum phase shift frequency fmin, the thickness L and/or the thermal conductivity and/or the heat capacity and/or the thermal diffusivity D of the layer and/or the thermal resistance of the layer/substrate interface C at the level of at least one point or at the level of each of the points.
• system 1 can return to its first configuration.
• a new layer of the part can be formed by sintering as described above. This new layer can then be controlled and/or characterized by modulated photothermal radiometry with synchronous detection as described above.
• FIGS. 3 A and 3B show a metal part 20 obtained by laser sintering.
• the metal part 20 is made of 316L stainless steel.
• FIG. 3A is a top view of the metal part, that is to say a side view of the face 21 of the part 20 intended to be irradiated by the laser beam 14.
• FIG. 3B is a sectional view section A-A of part 20.
• Piece 20 has the shape of a rectangular parallelepiped with a square base, with a side length of 30 mm, and a thickness equal to 7 mm.
• Part 20 comprises, from one of its main faces 21, respectively: - a first row of subsurface defect zones (cavities) 22a at 1.60 mm depth,
• the depth of a defect zone corresponds to the distance between the main face 21 intended to be irradiated by the laser beam 14c and the defect zone.
• the projection of each zone of subsurface defects on the main face 21 has the shape of a rectangle with a length approximately equal to 5 mm and a width approximately equal to 2 mm.
• FIG. 3C Shown in FIG. 3C is a mapping of the phase shifts 40 obtained by the method described previously for the part 20.
• the mapping of the phase shifts 40 was calculated using the software known under the name MATLAB.
• the laser beam 14a-c used for this achievement had a wavelength equal to 1.07 ⁇ m and a modulation frequency equal to 10 Hz with a power of 20 W.
• the diameter of the defocused laser beam 14c on the face 21 was from 7 mm to 1/e 2 in intensity.
• phase shifts 40 A "Fast-M2K Rapid IR Camera” camera from the company Telops was used to obtain this mapping of phase shifts 40.
• the mapping of phase shifts 40 is 320 pixels on the abscissa and 256 pixels on the ordinate, each pixel corresponding to 86 pm .
• the mapping of the phase shifts 40 comprises a first zone 41 whose phase shifts are close to each other, approximately equal to -55°, and two second zones 42 whose phase shifts are close to each other, approximately equal to -65°.
• the first zone 41 and the second zones 42 represent the surface irradiated from the face 21 by the laser beam 14c.
• the differences in phase shifts Atp between the first zone 41 and the second zones 42 are caused by the non-homogeneity of the part 20, that is to say variations in the physical and/or thermal properties within the part 20.
• these differences in Atp phase shifts are caused by the sub-surface defects of part 20.
• the second zones 42 represent the zones of sub-surface defects 22a of the first row.
• the second zones 42 have the shape of rectangles with a length approximately equal to 5 mm and a width approximately equal to 2 mm. These second zones 42 therefore have the same shape as the projections of the sub-surface defect zones (cavities) 22d on the face 21.

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• 2021
  • 2021-09-23 FR FR2110048A patent/FR3127289B1/fr active Active
• 2022
  • 2022-09-21 WO PCT/EP2022/076170 patent/WO2023046722A1/fr active Application Filing
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