Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C45/00—Amorphous alloys
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/36—Removing material
  • B23K26/38—Removing material by boring or cutting
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
  • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
  • B23K26/062—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam
  • B23K26/0622—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam by shaping pulses
  • B23K26/0624—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam by shaping pulses using ultrashort pulses, i.e. pulses of 1 ns or less
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/08—Devices involving relative movement between laser beam and workpiece
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/352—Working by laser beam, e.g. welding, cutting or boring for surface treatment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/36—Removing material
  • B23K26/362—Laser etching
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K2103/00—Materials to be soldered, welded or cut
  • B23K2103/08—Non-ferrous metals or alloys
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K2103/00—Materials to be soldered, welded or cut
  • B23K2103/18—Dissimilar materials
  • B23K2103/26—Alloys of Nickel and Cobalt and Chromium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C2200/00—Crystalline structure
  • C22C2200/02—Amorphous
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C45/00—Amorphous alloys
  • C22C45/04—Amorphous alloys with nickel or cobalt as the major constituent

Definitions

• the present invention relates to the field of methods for machining metal microcomponents, in particular amorphous metal alloy (AMA) parts.
• amorphous alloys have particularly interesting mechanical characteristics for technical fields involving very small parts.
• the difficulty is to carry out these machining operations of the AMAs while preserving their amorphous structure, guaranteeing a quality of the surface state of the machined part and maintaining a high cycle time adapted to industrial production.
• a machining operation that would lead to excessive heating of the material would cause crystallization of the heat-affected zone and would therefore lose the advantageous properties conferred by the amorphous structure of the material.
• imagining a laser machining process leaving long cooling times between two laser pulses is not compatible with industrial production.
• the invention proposes a method for machining an AMA sample with low thermal stability using a femtosecond laser, comprising at least one step of irradiating the sample with a laser beam along a reference trajectory for ablating material from the sample, open or not, along the reference trajectory so as to obtain a sample machined and maintained in an amorphous state, in which :
• the duration of each pulse is less than 1000 femtoseconds, preferably less than 600 femtoseconds, more preferably between 100 femtoseconds and 600 femtoseconds, and
• the pulsation frequency f of the laser beam 2 is greater than 20 kHz.
• the laser beam is mobile so as to move relative to the sample to be machined along the reference trajectory.
• the sample to be machined is mobile so as to move relative to the laser beam along the reference path.
• the amorphous metal alloy has:
• - a critical diameter of less than 5 millimeters, preferably less than 3 millimeters, and/or
• the scanning speed of the laser beam is less than 2000 mm/s, preferably less than 1000 mm/s and even more preferably less than 600 mm/s.
• the laser beam may be an infrared laser beam, in particular an infrared laser beam having a wavelength of between 800 nm and 1100 nm, in particular a wavelength of 1030 nm ⁇ 5 n.
• the laser beam may be a green laser beam, in particular a green laser beam having a wavelength between 500 nm and 540 nm.
• the wavelength may in particular be equal to 515 nm ⁇ 5 nm.
• the laser beam may be an ultraviolet laser beam, in particular an ultraviolet laser beam having a wavelength of less than 400 nm.
• the wavelength can in particular be equal to 343 nm ⁇ 25 nm.
• the laser beam may be a blue laser beam, in particular a blue laser beam having a wavelength of between 400 nm and 480 nm.
• the laser beam has a fluence greater than 15 J/cm2.
• the fluence is greater than 20 J/cm2.
• the fluence can be in the range of 40 J/cm2 to 400 J/cm2.
• each pulse of the laser beam irradiates a portion of the sample to be machined on the reference trajectory.
• the portion irradiated by a pulse at least partially covers the portion irradiated by the preceding pulse.
• the overlap between two portions irradiated by two successive pulses of the laser beam is at least 25% of the surface of the diameter of a portion irradiated by the laser beam.
• the overlap between two portions irradiated by two successive pulses of the laser beam is at most 95% of the area of the diameter of a portion irradiated by the laser beam.
• the step of irradiating the sample with a laser beam along the reference trajectory (TRef) is repeated at least once. This step is iterated preferably at least 100 times, and more preferably at least 300 times.
• the reference trajectory (TRef_p) during an iteration (R_p) coincides with the reference trajectory (TRef_p-1) of the previous iteration (R_p-1).
• the scanning speed of the laser beam is less than 2000 mm/s, preferably less than 1000 mm/s and even more preferably less than 600 mm/s.
• the scanning speed is greater than 30 mm/s, more preferably greater than 40 mm/s.
• the laser beam has a diameter projected onto the irradiated portion of the sample of less than 100 ⁇ m, preferably between 5 and 100 ⁇ m, preferably between 10 and 60 ⁇ m, more preferably between 10 and 30 p.m.
• the laser beam has an average power greater than 0.4 W.
• the average power is preferably greater than 1.5 W.
• the average power is more preferably between 1.5 W and 30 W .
• the movement of the laser beam comprises a precession movement.
• the precession angle of the laser beam is less than 10°, preferably less than 8°.
• an angle between the mean direction of the laser beam and the direction normal to the surface of the irradiated portion of the sample is less than 10°, preferably less than 8°.
• the laser beam has a variable focusing altitude.
• the altitude of the focal plane of the precession ring can be mobile and move in the direction of the sample as the machining progresses; and or the elevation of the focal plane of the individual beam can move towards the sample or within said sample as the machining progresses; the focusing altitude at the start of the machining being between the altitude of the focal plane of the precession ring and the altitude of the focal plane of the individual beam.
• the machining process is carried out by implementing at least one contour along at least one trajectory (TRef+n), n being the total number of contours implemented , the method thus comprising:
• the reference trajectory (TRef+n) being adjacent to the reference trajectory (TRef+(n-1)) and translated by a given distance gn from said reference trajectory (TRef+n-1) in the direction opposite to that of the trajectory (TRef), and
• Steps (a) and/or (b) and/or, optionally (c) can be repeated, preferably successively, until a machined part is obtained and maintained in the amorphous state.
• the machining is carried out in several iterations on the same trajectory, without the supply of gas or other cooling systems.
• the energy of the laser beam per mm traveled during passage over a trajectory is preferably less than 0.8 J/mm, preferably between 0.03 J/mm and 0.8 J/ mm.
• the amorphous metal alloy of the sample to be machined contains, in atomic percentage, more than 40% of Ni, Zr, Cu, Ti, Fe or Co.
• the amorphous metal alloy of the sample to be machined contains, in atomic percentage, more than 50% of Ni, Zr, Cu, Ti, Fe or Co.
• the amorphous metal alloy of the sample to be machined contains in atomic fraction more than 50% of the elements Ni and Nb.
• the amorphous metal alloy of the sample to be machined contains in atomic fraction more than 60% of the elements Ni and Nb, more preferably more than 70% of the elements Ni and Nb.
• the invention also relates to a method for producing a surface of an amorphous metal alloy sample using a femtosecond laser, the method comprising at least one step of irradiating with a laser beam a first surface of the sample so as to obtain a second surface whose roughness Ra is less than 400 nm, preferably less than 200 nm, more preferably less than 100 nm; and in which:
• the duration of each pulse is less than 1000 femtoseconds, preferably less than 600 femtoseconds, more preferably between 100 femtoseconds and 600 femtoseconds, and
• the amorphous metal alloy has:
• - a critical diameter of less than 5 millimeters, preferably less than 3 millimeters, and/or - a difference between the crystallization temperature and the glass transition temperature of less than 60°C, and/or
• the invention also relates to a method for cutting an amorphous metal alloy sample using a femtosecond laser, the method comprising at least one step of irradiating with a laser beam a first surface of the sample on one face F1 so as to obtain a second face F2 such that at each point of intersection of the faces F1 and F2, said faces F1 and F2 form between them an angle of 90° ⁇ 1.5°, preferably 90° ⁇ 1°, more preferably 90° ⁇ 0.5°; and in which:
• the duration of each pulse is less than 1000 femtoseconds, preferably less than 600 femtoseconds, more preferably between 100 femtoseconds and 600 femtoseconds, and
• the amorphous metal alloy has: - a critical diameter of less than 5 millimeters, preferably less than 3 millimeters, and/or
• the invention also relates to a process for manufacturing an amorphous metal alloy part, comprising the steps:
• finishing step on at least the surface of the machined sample, preferably a tribofinishing step.
• the invention also relates to a microcomponent, in particular a mechanical microcomponent, made of amorphous metal alloy comprising at least one surface machined according to the method for producing a surface described previously or according to the cutting method described previously.
• FIG. 39 [39]
• Fig 1] represents an X-ray diffraction analysis of an amorphous metallic alloy
• FIG. 10 represents an X-ray diffraction analysis of a partially amorphous metal alloy
• FIG. 1 represents an X-ray diffraction analysis of a crystalline metal alloy
• FIG. 4 represents a schematic sectional view of a laser beam
• FIG. 5 is a schematic side view of an installation capable of implementing a process for machining an amorphous metal alloy sample
• FIG. 6 is a schematic top view illustrating an embodiment of the machining process
• FIG.7 is a schematic side view illustrating two modes of implementation of the machining process
• FIG. 8 is a schematic view detailing an embodiment of the machining process
• FIG. 9 is a schematic side view detailing an optional feature of the process
• FIG. 10 is a schematic sectional view detailing the optional feature of Figure 9,
• FIG. 11 is a schematic top view detailing the optional feature of Figure 9,
• FIG. 12 is a schematic top view detailing another optional feature of the process
• FIG. 13 is a schematic side view detailing another optional feature of the process
• FIG. 14 is a diagram of the geometry machined in example 1,
• FIG. 15 is a diagram representing the results of the bending tests of Example 2.
• Amorphous metal alloy or “AMA” or “metal glass” means metals or metal alloys that are not crystalline, that is to say whose atomic distribution is mostly random. Nevertheless, it is difficult to obtain a one hundred percent amorphous metallic glass because most often a fraction of the material remains which is crystalline in nature. This definition can therefore be generalized to metals or metal alloys which are partially crystalline and which therefore contain a fraction of crystals, as long as the amorphous fraction is predominant. Generally, the fraction of the amorphous phase is greater than 50%.
• amorphous metal alloy or "AMA” or “metal glass” therefore means metals or metal alloys whose fraction of the amorphous phase is greater than 50%, preferably greater than 65%, more preferably greater than 75% and more preferably still greater than 80%.
• a metallurgical structure is said to be amorphous or entirely amorphous when an analysis by X-ray diffraction (method of analysis which will subsequently be called DRX) as described below does not reveal peaks of crystallization.
• critical diameter (noted De) of a specific metal alloy is understood to mean the maximum thickness limit below which the metal alloy has a completely amorphous metallurgical structure or beyond which it is no longer possible to obtain a completely amorphous metallurgical structure, when the metal alloy is cast from a liquid state and is subjected to rapid cooling such that the transfer of heat inside the metal alloy is optimal. More specifically, the critical diameter is determined by successive moldings of cylindrical bars, generally longer than 50 mm and of different diameters, molded from the liquid state under the following conditions:
• the alloy is melted at a temperature of Tl + 150°C with Tl, the liquidus temperature of the alloy (in °C);
• the alloy is cast in a CuC1 type copper mold and is cooled to a maximum temperature of about twenty degrees Celsius (20°C).
• the alloy is produced and molded under an inert, high-purity atmosphere (eg under argon of quality 6.0) or under a secondary vacuum (pressure ⁇ 10 4 mbar).
• an inert, high-purity atmosphere eg under argon of quality 6.0
• a secondary vacuum pressure ⁇ 10 4 mbar
• the alloy is cast with a system allowing the application of a pressure differential to facilitate the casting of the alloy and to ensure intimate contact between the alloy and the walls of the mold in order to ensure the rapid cooling of the alloy.
• the molding step can be carried out under a pressure of 20 MPa.
• This overpressure application system can be mechanical (piston) and/or gaseous (application of an overpressure).
• the bars are cut in order to obtain a slice, that is to say a transverse section of the cylinder, preferably located towards the middle of the bar, and with a thickness of between 1 and 10 millimeters.
• the slices obtained are analyzed by X-ray diffraction to determine whether they have an amorphous or partially crystalline structure.
• the critical diameter is then determined as being the maximum diameter for which the structure is amorphous.
• the presence of bumps characteristic of amorphous metal alloys is then highlighted by X-ray diffraction. Given that there are most often defects in the metallurgical structures, a 100% amorphous alloy is almost impossible to obtain and the critical diameter can be defined as the diameter above which an X-ray diffraction analysis clearly shows crystallinity peaks.
• Figure 1 is an XRD analysis of a metal alloy in the amorphous state.
• Figure 2 is a similar analysis performed on a partially amorphous alloy. In this figure, we find the bump characteristic of amorphous structures, but with the presence also crystallinity peaks.
• Figure 3 is a similar analysis performed on a crystalline alloy. In figure 3, the bump characteristic of AMAs is not present, and the crystallinity peaks are clearly visible.
• AMA with low thermal stability means a metal alloy having:
• a critical diameter De of less than 5 millimeters, preferably less than 3 millimeters, and/or
• a quotient (ATx/(TI-Tg)), corresponding to the quotient of the difference DTc between the crystallization temperature Tx and the glass transition temperature Tg and of the difference between the liquidus temperature Tl and the glass transition temperature Tg , less than 0.12, preferably less than 0.1.
• Machining means removal of material from a sample 1. Removal of material means removal of material, the two terms being equivalent. Thus, in the context of the present application, “ablating" material and “removing” material are equivalent terms. Machining can be through, as is the case for cutting or drilling. In other words, the laser beam removes material until it passes through the sample. Machining can be blind, as is the case for engraving, blind drilling, surfacing, for example to obtain a given roughness, or even for producing surfaces or flanks whose angle formed between them has excellent precision, for example an angle of 90° ⁇ 1.5°, preferably 90° ⁇ 1°, more preferably 90° ⁇ 0.5°. Non-emergent machining leaves a thickness of unmachined material.
• microcomponent means a component of small dimensions, for example a component of which at least one of the dimensions does not exceed 2 millimeters (mm), or even 1 mm, preferentially 200 microns (pm), more preferentially 100 pm or even 50 pm.
• mechanical microcomponent means a microcomponent capable of cooperating with one or more other microcomponents.
• fluence of the laser beam means the “peak fluence” of the laser beam, the energy delivered per unit area. It is expressed in J/cm 2 .
• diameter D or “spot diameter” of the laser beam is meant the diameter of the portion 3 irradiated on the sample 1 by the laser beam 2.
• the diameter D is therefore the diameter of the laser beam 2 focused on the sample 1.
• the laser beam 2 is of Gaussian shape.
• the laser beam 2 is a Gaussian beam. Consequently, the diameter of the irradiated portion 3 depends on the distance between the emission point of the laser beam 2 and the irradiated portion 3.
• Diameter D sometimes called spot diameter, can also be called diameter of portion 3 irradiated on sample 1 or diameter of laser beam 2 focused on sample 1.
• the laser beam 2 can be animated with a precession movement.
• the precession movement of the laser beam 2 is schematized in FIG. 9 and part B of FIG. 4.
• a schematic sectional view of two positions of the same laser beam 2 driven by a precession movement is schematized .
• the actual displacement of the laser beam 2 thus corresponds to the composition of two displacements.
• the first movement is a movement along a setpoint trajectory TC.
• the second movement is the precession movement.
• the precessional movement therefore makes it possible to change the angle of incidence of the beam throughout the machining process.
• the zone irradiated by the laser beam 2 on the sample 1 to be machined describes a trochoidal trajectory.
• the reference trajectory TRef is then a trochoid.
• Part B of FIG. 11 is an enlargement of a portion of part A.
• the setpoint trajectory TC appears to be almost rectilinear.
• the reference trajectory TRef coincides with the setpoint trajectory TC.
• the reference trajectory TRef describes loops moving along the setpoint trajectory TC.
• the laser beam 2 oscillates around its average direction D2 and describes the shape of a cone with an angle of attack with respect to the surface of the sample 1.
• the angle of incidence of the laser beam 2 therefore changes during the machining process.
• focal plane of the precession ring (“Best Focus Global Beam” in English, also indicated by the acronym “BFG”) means the focal plane where the individual laser beam 2 is defocused and rotates almost on itself during precession. Part B of Figure 4 illustrates the notion of the precession ring focal plane (BFG).
• focusing altitude with a precessional movement is meant the distance between the upper surface of the sample 1 and the focal plane where the individual laser beam 2 is defocused and rotates almost on itself during the precession (BFG).
• FIG. 5 There is shown schematically in Figure 5 a laser cutting installation 20.
• the installation comprises an enclosure 13 in which is placed a laser transmitter 14 capable of emitting a laser beam 2.
• a sample 1 is placed opposite the point of emission of the laser beam 2.
• the sample 1 can thus be irradiated by the laser beam 2, i.e. the laser beam 2 can reach a part of the surface S of sample 1 and interact with the material of sample 1.
• the portion of sample 1 irradiated by the laser beam 2 is designated by the reference sign 3.
• Sample 1 can be fixed on a plate 6 acting as a support.
• the laser beam 2 can be mobile so as to move relative to the sample 1.
• the sample 1 can then be immobilized relative to the enclosure 13 of the installation 20.
• An electronic control unit 25 makes it possible to control the instants of triggering and interruption of the laser beam 2, as well as the displacement movements of the laser beam 2 with respect to the sample 1.
• the reference trajectory TRef can thus be controlled in real time.
• the sample 1 to be machined can be mobile so as to move relative to the laser beam 2.
• the sample 1 to be machined is fixed to a mobile plate along at least 2 axes.
• the laser beam 2 and the sample 1 to be machined can both be mobile, successively or concomitantly, in particular to facilitate the machining of complex parts. In all cases, there is a relative movement of the laser beam 2 with respect to the sample 1 so as to obtain a displacement of the laser beam 2 along the reference trajectory TRef.
• Sample 1 to be machined can have any shape and the portion of sample 1 to be ablated can also be of any shape, emerging or not.
• the sample 1 to be machined is flat.
• sample 1 to be machined is an amorphous metal alloy plate.
• the thickness of sample 1 to be machined is preferably between 5 ⁇ m and 2 mm, preferably between 10 ⁇ m and 1 mm.
• the sample 1 to be machined is a cylinder or comprises a cylindrical part and the method aims to arrange an axis, crossing or not, within said cylinder or said part cylindrical.
• the diameter of the microcomponent resulting from the machining process preferably has a diameter, preferably a maximum diameter, less than or equal to 2 mm.
• the amorphous metal alloy of sample 1 to be machined may, for example, contain in atomic fraction more than 40% Nickel (Ni), preferably more than 50% Nickel (Ni).
• the amorphous metal alloy of sample 1 to be machined contains in atomic fraction more than 50% of the elements Nickel (Ni) and Niobium (Nb), preferably more than 60% of the elements Nickel (Ni) and Niobium (Nb), more preferably more than 70% of the elements Nickel (Ni) and Niobium (Nb).
• the alloy with low thermal stability can also be chosen from alloys based on Zr, Cu, Ti, Fe or Co.
• the term "based on” means that the element cited constitutes the major element of the alloy.
• the present invention proposes a method for machining a sample 1 of amorphous metal alloy using a femtosecond laser, comprising at least one step of irradiating the sample 1 with a laser beam 2 the along a reference trajectory TRef to ablate material from sample 1, open or not, along the reference trajectory TRef so as to obtain a sample 1 machined and maintained in the amorphous state, in which :
• the duration of each pulse is less than 1000 femtoseconds, preferably less than 600 femtoseconds, more preferably included between 100 femtoseconds and 600 femtoseconds, and
• the pulsation frequency (f) of the laser beam (2) is greater than 20 kHz;
• the laser beam 2 is mobile so as to move relative to the sample 1 to be machined along the reference trajectory TRef, or
• the sample 1 to be machined is mobile so as to move relative to the laser beam 2 along the reference trajectory TRef.
• the amorphous metal alloy of sample 1 is an alloy of low thermal stability.
• the laser beam 2 is mobile so as to move relative to the sample 1 to be machined along the reference trajectory TRef.
• the scanning speed of the laser beam 2 is less than 2000 mm/s, preferably less than 1000 mm/s and even more preferably less than 600 mm/s.
• the scanning speed of the laser beam may be from 10 mm/s to 500 mm/s, preferably from 25 mm/s to 250 mm/s, more preferably from 50 mm/s to 200 mm/s or even from 100 mm/s to 200 mm/s.
• Figure 6 illustrates the concept of sample 1, machined sample 1 and/or part 4.
• Sample 1 forms the raw material or preform to be machined. After one or more machining operations, a machined sample 1 or part 4, also called a microcomponent, is obtained.
• Part 4 can be a detached part of sample 1, in particular when the process is a cutting process, also called through machining.
• the sign 9 schematizes the circumference 9 of the part 4.
• the shape of the part 4 can be arbitrary.
• part 4 is entirely included within the perimeter 21 of sample 1. According to an example not shown, part of the perimeter 21 of sample 1 can form part of the part 4.
• the relative trajectory TRef can define a part of the perimeter 9 of the part 4.
• the machining process can be implemented in order to form only a part of the perimeter 9 of the part 4.
• the rest of the perimeter 9 of part 4 can be obtained by other methods or machining processes.
• a part of the periphery 9 of the microcomponent 4 can also be formed by a portion of the periphery 21 of the sample 1, which then remains raw in this zone.
• the machined sample or part 4 can be sample 1 from which part of the initial material has been ablated without the material being ablated. emerging.
• the concept of non-emergent ablation is illustrated in particular in Figure 8.
• sample 1 can be a cylinder and the portion to be ablated 8 can be such that it allows a bearing to be machined in part 4. It It can be for example a bore, emerging or not, within the part 4, which can cooperate with an axis.
• the machining process can make it possible to machine a pivot, for example of conical shape, terminating a cylindrical portion, in particular an axe.
• the ablated area is shown in dotted lines in Figure 7 and bears the reference 21.
• pulsed laser is meant the fact that the laser beam 2 is applied in successive pulses. In other words, a pulse of the laser beam 2 is applied for a duration t1, then the application of the laser beam is stopped for another duration t2.
• the frequency f at which the pulses are applied is called the pulsation frequency or repetition rate of the laser beam 2. This frequency f is equal to the inverse of the period T, which is the sum of the durations t1 and t2.
• Figure 8 illustrates the application of successive pulses of laser beam 2.
• Column A of Figure 8 is a top view of sample 1.
• Column B is the corresponding side view.
• Each pulse of the laser beam 2 irradiates a portion 3 of the sample 1 to be machined, and the portion 3 irradiated by a pulse l_n at least partially covers the portion 3 irradiated by the previous pulse l_n-1.
• the successive pulses are applied from left to right.
• the sign l_1 schematizes the portion irradiated by the first pulse applied.
• I_2 schematizes the portion irradiated by the second applied pulse.
• I_7 which schematizes the portion irradiated by the seventh applied pulse, is the last pulse represented. The impulses can of course continue.
• Two successive pulses are applied with a spatial offset d.
• the offset d between two portions irradiated by two successive pulses l_n-1, l_n of the laser beam 2 is preferably such that there is at least partial overlap for two successive irradiated portions l_n-1, l_n.
• each pulse of the laser beam 2 irradiates a portion 3 of the sample 1 to be machined on the reference trajectory Tref, the portion 3 irradiated by a pulse l_n at least partially covers the portion 3 irradiated by the pulse previous l_n-1, and the overlap between two portions 3 irradiated by two successive pulses l_n-1, l_n of the laser beam 2 is at least 25% of the area of the diameter D of a portion 3 irradiated by the laser beam 2 and at most 95% of the surface of the diameter D of a portion 3 irradiated by the laser beam 2.
• the portion 3 irradiated by a pulse l_n of the laser beam 2 is offset here with respect to the portion irradiated by the previous pulse l_n-1 by a distance d less than the diameter D of the laser beam 2.
• the diameter D of an irradiated portion 3 corresponds to the spot diameter of the laser beam 2.
• the diameter D of the spot of the laser beam 2 or diameter D of the laser beam projected on the portion 3 of the sample 1 is preferably less than 100 ⁇ m, preferably between 5 and 100 ⁇ m, preferably from 10 to 60 ⁇ m, more preferably 10 to 30 ⁇ m.
• the pulse frequency f of the laser beam 2 is greater than 20 kHz. More preferably, the pulsation frequency f of the laser beam 2 is between 20 kHz and 400 kHz, preferably between 20 kHz and 300 kHz, more preferably still between 40 kHz and 250 kHz, or even greater than or equal to 50 kHz and up to at 200 kHz, or even greater than or equal to 75 kHz and up to 150 kHz.
• the laser beam 2 may be an infrared laser beam, in particular an infrared laser beam having a wavelength of between 800 nm and 1100 nm, in particular a wavelength of 1030 nm ⁇ 5 nm.
• the laser beam 2 can also be a green laser beam, in particular a green laser beam having a wavelength of between 500 nm and 540 nm, in particular a wavelength of 515 nm ⁇ 5 nm.
• the laser beam 2 can also be an ultraviolet laser beam, in particular an ultraviolet laser beam having a wavelength of less than 400 nm, in particular a wavelength of 343 nm ⁇ 25 nm.
• the laser beam 2 can also be a blue laser beam, in particular a blue laser beam having a wavelength comprised between 400 nm and 480 nm.
• the absorption rate of the material of sample 1 is a function of the wavelength/material couple of said sample 1.
• the wavelengths in the green generally have a better absorption rate. absorption, which promotes the ablation of the material.
• the lower the wavelength the more expensive the process will be.
• the laser beam 2 has a peak fluence greater than 15 J/cm2, preferably greater than 20 J/cm2, from 40 J/cm2 to 400 J/cm2.
• the fluence is the level of energy required per unit area to ablate the material, i.e. to remove material from the area irradiated by the laser beam. It depends on the energy and the diameter of the laser beam. For example, for a Gaussian type beam, the fluence is calculated according to the following formula:
• the fluence is calculated in the initial configuration, i.e. from the diameter D of the beam at time tO of the machining process.
• the laser beam 2 has an average power greater than 0.4 W, preferably greater than 1.5 W, more preferably from 1.5 W to 30 W, even more preferably from 1.5 W to 15 W, or even from 1.5 W to 10 W.
• the power (in watt W) is the product of the energy (in joule J) and the frequency of the laser (in s 1 ).
• the power of the laser beam 2 selected is preferably between 0.425 W and 20 W.
• the laser beam 2 is moved along the reference trajectory TRef according to a scanning speed of less than 2000 mm/s.
• the scanning speed is less than 1000 mm/s, and even more preferably is less than 600 mm/s.
• the step of irradiating sample 1 with a laser beam 2 along a relative reference trajectory TRef is iterated at least once, preferably at least 100 times, more preferably at least 300 times.
• the number of iterations is adapted according to the quantity of material to be ablated.
• the relative reference trajectory TRef during an iteration R_p coincides with the relative reference trajectory Tref of the previous iteration R_p-1.
• Line L1 of FIG. 8 schematizes the first passage of the laser beam 2.
• Line L2 schematizes the second passage of the laser beam 2, that is to say the iteration of higher rank with respect to the preceding iteration.
• Line L3 schematizes the third pass, again the iteration of higher rank with respect to the preceding iteration.
• the solid circles describe the portions irradiated during the present iteration and the dotted circles describe the portions irradiated during a previous iteration.
• the laser beam 2 can always scan the same trajectory until obtaining the ablation of material corresponding to the thickness of remaining material desired. The thickness of remaining material is zero when the machining is through.
• the depth p of the zone where the material has been ablated increases progressively, as measurement of the repetitions of the passage of the laser beam 2 along the reference trajectory TRef.
• the machining is carried out in several iterations on the same trajectory, without the supply of gas or other cooling systems.
• the energy of the laser beam per mm traveled during passage over a trajectory is preferably less than 0.8 J/mm, preferably between 0.03 J/mm and 0.8 J/ mm.
• the movement of the laser beam 2 comprises a precession movement.
• the precession movement notably makes it easier to obtain machining with straight flanks.
• the precession angle A1 of the laser beam 2 is preferably less than 10°, preferably less than 8°.
• the precession movement of the laser beam 2 delimits a zone of width dp.
• the precession angle A1 corresponds to the angle between the average direction D2 of the laser beam 2 and the instantaneous direction Di of the laser beam 2 during precession.
• the precession speed of the laser beam 2 is from 500 rpm (or rpm) to 40,000 rpm (or rpm), preferably between 500 rpm and 10,000 rpm, even more preferably between 500 rpm min and 3000 rpm.
• the ablation of material produced by the laser beam 2 to which a precessional movement is applied may substantially have a W-shape, thus making it possible to limit the concentration of energy in a precise zone of the sample 1 to be machined.
• flanks 16 such that they form between them an angle Ad of 90° ⁇ 1.5°, preferably of 90° ⁇ 1°, plus preferentially 90° ⁇ 0.5°
• the average direction D2 of the laser beam 2 forms an angle A2 with the direction normal to the surface of the portion 3 irradiated by said laser beam 2 comprised between 80° and 90°, preferentially comprised between 82° and 90°.
• an angle A2 between the mean direction D2 of the laser beam 2 and the direction normal to the surface of the irradiated portion 3 of the sample 1 is less than 10°, preferably less than 8°.
• the laser beam 2 is thus inclined with respect to the direction Y normal to the surface of the irradiated portion 3 of the sample 1.
• This angle of inclination A2 makes it possible to improve the perpendicularity of the sides 16 of the machined part 4.
• the angle of inclination A2 makes it possible to compensate for the perpendicularity defects linked to the fact that the laser beam 2 is Gaussian.
• the laser beam 2 can have a variable focusing altitude.
• the elevation of the focal plane of the precession ring (BFG) can be mobile and descend in the direction of the sample as the machining progresses; and/or the Individual Beam Focal Plane (BFI) elevation may move toward Sample 1 or within Sample 1 as machining progresses; the focus altitude at the beginning of the machining being between the altitude of the focal plane of the precession ring (BFG) and the altitude of the focal plane of the individual beam (BFI).
• the diameter D of the irradiated portion depends on the thickness of material already removed by the laser beam 2.
• This embodiment is therefore particularly advantageous for maintaining a diameter D irradiated constant over at least part of the machining process, as the machining progresses and the material is ablated.
• This embodiment makes it possible in particular to improve the cycle time of the machining process.
• the machining of the sample 1 can be carried out by a strategy of successive cuts which converge towards the final shape desired for the part 4.
• the first cut or cuts made are one or more contours.
• the last The cut made gives the part the desired geometry in the area treated by the laser beam.
• the machining process is carried out by the implementation of at least one outline (also called "outline” in English) according to at least one trajectory TRef+n, n being the total number of outlines placed implemented.
• This embodiment is illustrated in Figure 12.
• three contours have been produced.
• the first contour is produced along the reference trajectory TRef2.
• the second contour schematized by a second reference trajectory TRefl, is shifted by a distance g2 with respect to the first contour.
• the third contour schematized by a third reference trajectory, corresponding to the final machining reference trajectory of part 4, i.e. the reference trajectory TRef.
• the trajectory TRef is shifted by a distance g1 with respect to the second contour.
• the method comprises:
• the reference trajectory TRef+n is adjacent to the reference trajectory TRef+(n-1) and translated by a given distance g2 from said reference trajectory TRef+n-1 in the direction opposite to that of the trajectory TRef.
• the given distances g1 , g2, gn between two reference trajectories directly adjacent TRef; TRef+1, TRef+(n-1); TRef+n are such that the pulses of the laser beam 2, irradiating the sample 1 to be machined on the first reference trajectory TRef; TRef+1, TRef+(n-1) or TRef+n, also irradiates, at least partially, the sample 1 to be machined on the reference path(s) TRef; TRef+1, TRef+(n-1) or TRef+n which is or are directly adjacent to it.
• the distances g1, g2, gn can be identical or different.
• Steps (a) and/or (b) and/or, optionally (c) can be repeated, preferably successively, until a part 4 machined according to the desired final geometry is obtained, and maintained in the amorphous state.
• the laser beam 2 machining process can optionally be coupled with the presence of a gas flow on the sample 1 to be machined.
• the machining process can thus include the step:
• the flow of gas 10 is then maintained during all or part of the machining process.
• a blow nozzle 11, shown schematically in Figure 5 guides the gas flow 10 to the sample 1.
• the flow of gas 10 also makes it possible to evacuate the particles originating from the ablation of material by the laser beam 2.
• the flow of gas 10 sent to the sample 1 to be machined is an air flow.
• the gas flow 10 sent to the sample 1 to be machined can also be an inert gas flow.
• the flow of gas 10 sent to sample 1 is blown in a direction coaxial with the direction of the laser beam.
• the gas flow may also not be coaxial with the direction of the beam.
• the sample 1 to be machined can be protected from oxidation during the cutting operation.
• the cutting process may include the step:
• the enclosure 13 in which the sample 1 and the laser beam 2 are advantageously contained can thus contain a protective medium 12.
• the protective medium 12 from oxidation is a gas whose pressure is lower than atmospheric pressure.
• the protective medium 12 from oxidation is an inert gas.
• the process may include the step:
• sample 1 can be cooled during the cutting operation.
• sample 1 to be machined is thermally coupled to a plate 6 comprising a cooling system 7 configured to absorb heat from sample 1 to be machined.
• the sample 1 to be machined can be fixed to the plate 6.
• the cooling system 7 also contributes to avoiding an excessive rise in temperature of the sample 1 during the machining process.
• the cooling system 7 may include a Peltier effect module configured to exchange heat with the plate 6. Alternatively or additionally, the cooling system 7 may include a heat transfer fluid circuit configured to exchange heat. heat with the plate 6. Other means of cooling are also possible.
• Sample 1 can also be completely or partially immersed in a heat transfer liquid. The heat transfer liquid can be static or in motion (flow).
• the invention also relates to a method for producing a surface of a sample 1 in amorphous metal alloy with low thermal stability using a femtosecond laser.
• Said method comprises at least one step of irradiating with a laser beam 2 a first surface of the sample 1 so as to obtain a second surface whose roughness Ra is less than 400 nm, preferably less than 200 nm, more preferably less than 100 nm.
• the laser beam 2 is pulsed and the duration of each pulse is less than 1000 femtoseconds, preferably less than 600 femtoseconds, more preferably between 100 femtoseconds and 600 femtoseconds; and the pulsation frequency f of the laser beam 2 is greater than 20 kHz.
• the invention also relates to a method for cutting a sample 1 of an amorphous metal alloy with low thermal stability using a femtosecond laser.
• the process comprises at least one step of irradiating with a laser beam 2 a first surface of the sample 1 on a face F1 so as to obtain a second face F2 such as in each point of intersection of faces F1 and F2, said faces F1 and F2 form between them an angle Ad of 90° ⁇ 1.5°, preferably 90° ⁇ 1°, more preferably 90° ⁇ 0.5°.
• the laser beam 2 is pulsed, and the duration of each pulse is less than 1000 femtoseconds, preferably less than 600 femtoseconds, more preferably between 100 femtoseconds and 600 femtoseconds; and the pulsation frequency f of the laser beam 2 is greater than 20 kHz.
• the invention also relates to a process for manufacturing a part 4 in an amorphous metal alloy.
• the manufacturing process includes the steps:
• the manufacturing process includes the step:
• the invention relates to a microcomponent, in particular an AMA mechanical microcomponent comprising at least one surface 8 machined according to at least one of the preceding methods.
• the AMA microcomponent advantageously has an elastic deformation capacity of at least 1.2%, preferably at least 1.5%
• the micromechanical component may for example be an element of a clockwork mechanism for a mechanical watch, such as a date finger, a toothed wheel, or even an axis.
• a mechanical watch such as a date finger, a toothed wheel, or even an axis.
• the combination of the intrinsic mechanical properties of amorphous alloys and the precision of the cut made by the method makes it possible to provide micromechanical components particularly suited to this application. It can also be a microcomponent for the medical field, such as an implant.
• Ni(57-67)Nb(28-38)Zr(0-10) (atomic percentages) were cut with different sets of parameters detailed in Table 1 to validate the maintenance of the amorphous structure of the alloy of the samples machined according to the method of the invention.
• the Ni(57-67)Nb(28-38)Zr(0-10) alloy (atomic percentages) has low thermal stability within the meaning of the invention. Indeed, its critical diameter De is only 3 mm, its stability coefficient, i.e. its quotient (ATx/(TI-Tg)) of 0.07 and its DTc is equal to 40.
• the samples were cut from 500 ⁇ m thick preforms and a pyramidal shape was chosen to study the influence of the width of the cut on the thermal allocation of the material.
• Figure 14 shows a diagram of the machined geometry seen from above, the geometry representing the perimeter of the part.
• Table 1 summarizes the range of parameters tested. Three sets of settings were tested.
• microstructural analyzes as well as the X-ray diffraction analyzes showed conservation of the amorphous microstructure for all the clearances tested, even for the finest areas of the sample, which are the pointed areas.
• Example 2 Maintenance of mechanical performance
• Figure 15 represents the value of the elastic limit in bending, expressed in MPa, for the four samples of table 3.
• the sample noted 3.4 has not undergone laser machining and serves as a representative control of the properties to be the amorphous state.
• Example 3 Obtaining the desired quality (dimensional and geometric) and influence on the rates
• the surface condition after machining is an essential property for many microcomponents.
• a low Ra and good perpendicularity of the flanks are essential to control tribological contacts and obtain coefficients of friction and low wear rates, which make it possible to optimize the yields of mechanical systems (conservation of energy) and their lifespan.
• the important quality criteria include the roughness of the machined surfaces, the obtaining of straight flanks, i.e. the perpendicularity between the machined flank and the adjacent flanks, as well as the obtaining of non-oxidized parts and without redeposition of particles (burrs).
• Table 5 summarizes the results for sets of parameters (machining in air, without nozzle) of preforms, in AMA such as example 1, machined by a pulsed laser beam of 320 fs, and having a 515 nm wavelength: - Set 1: Low power during machining
• the material can therefore be machined with higher powers, which makes it possible from an economic point of view to increase the cutting rates.
• Example 4 Optimization of cutting rates
• the focusing altitude is fixed at the start of machining. It is the latter which allows in particular to define the diameter of the theoretical spot at the start of machining as well as the fluence.
• the focus altitude remains fixed during machining. The process becomes less efficient as the depth of cut increases, that is to say, as one moves away from the ideal focal point to ablate the material.

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• 2021
  • 2021-06-30 FR FR2107113A patent/FR3124752B1/fr active Active
• 2022
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