PART HAVING A POROUS STRUCTURE AND RELATED MANUFACTURING METHOD

Abstract

A part including a porous structure including cellular pores and formed at least in part by the periodic repetition of a basic pattern, each cellular pore being delimited by a wall, made of a metal or a polymer, having a parietal porosity greater than 5% and including parietal pores with a mean size less than the mean size of the cellular pores.

Claims

1. A part comprising a porous structure comprising cellular pores and formed at least in part by the periodic repetition of a basic pattern, each cellular pore being delimited by a wall, made of a metal or a polymer, having a parietal porosity greater than 5% and comprising parietal pores with a mean size less than the mean size of the cellular pores.

2. The part according to claim 1, wherein the mean size of the cellular pores is at least 20 times greater than the mean size of the parietal pores.

3. The part according to claim 1, wherein the mean size of the parietal pores is less than 500 .Math.m.

4. The part according to claim 3, wherein at least 85% of the parietal pores are smaller than 200 .Math.m.

5. The part according to claim 4, wherein more than 50% of the parietal pores are smaller than 50 .Math.m.

6. The part according to claim 1, wherein the porous structure is made of a metal.

7. The part according to claim 1, wherein the porous structure comprises one of the following metals: aluminium, nickel, cobalt, iron, copper, palladium, titanium, tungsten, silver, platinum and alloys thereof.

8. The part according to claim 1, wherein the parietal porosity is between 5% and 80%.

9. The part according to claim 1, wherein the cell porosity is greater than 70% and/or less than 97%.

10. A method for manufacturing a part according to claim 1, wherein the method involves producing the porous structure by shaping a powder using an additive manufacturing technique.

11. The method according to claim 10, wherein the additive manufacturing technique is a powder-bed additive manufacturing technique.

12. The method according to claim 11, wherein the additive manufacturing technique involves the partial or complete fusion of powder particles using a light beam or an electron beam.

13. The method according to claim 12, wherein the additive manufacturing technique involves the partial or complete fusion of powder particles using a light beam.

14. The method according to claim 13, wherein the ratio of the energy density of the light beam to the threshold energy density is between 0.3 and 0.9, the threshold energy density being the energy density above which a porous structure with dense walls is obtained.

15. The method according to claim 10, wherein the median diameter of the particles of the powder is between 1 .Math.m and 100 .Math.m.

16. The method according to claim 13, wherein the additive manufacturing technique involves repeating a cycle comprising the deposition of a powder layer of thickness (e) of between 6 .Math.m and 200 .Math.m, and irradiating at least a portion of the layer using the light beam.

17. The method according to claim 13, wherein the following steps are executed before production of the porous structure: (i) manufacturing at least one test structure with different respective light beam powers in order to determine the threshold energy density E.sub.threshold above which the porous structure with dense walls is obtained, the movement speed V.sub.0 of the light beam, the shift value HD.sub.0 of the light beam, and the thickness of the layer e.sub.0 being predetermined and kept constant during manufacture of said at least one test structure, (ii) selecting at least one of the following parameters: movement speed of the light beam, shift value of the light beam, and thickness of the layer so that the energy density of the light beam during the subsequent manufacturing step is less than E.sub.threshold.

18. A shock absorbing device formed at least in part by a part according to claim 1.

19. A device comprising a part according to claim 1, said device being a vehicle, a porous tank, a shim or an acoustic damper.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0078] The invention can be better understood from the detailed description of the example given below and the attached drawing, in which:

[0079] [FIG. 1] FIG. 1 is a photograph of an example part according to the invention, as well as an optical microscopy photograph of a wall of the part,

[0080] [FIG. 2] FIG. 2 is a schematic view of different examples of the basic pattern repeated to form a porous structure according to the invention, and

[0081] [FIG. 3] FIG. 3 is a schematic view of an example embodiment of an additive manufacturing method on a powder bed using a laser beam (A) in a configuration without overlapping (B) and with overlapping (C).

DETAILED DESCRIPTION

[0082] An example part 10 according to the invention is shown in FIG. 1.

[0083] The part is a cube of dimensions 50×50×50 mm.sup.3. The part has a porous structure 15 comprising open cellular pores 20 and metal walls 30, each of which delimits one or more cellular pores and forms a partition between adjacent cellular pores.

[0084] The cellular pores 20 have a substantially spherical shape with a diameter of 5.6×5.6 mm.sup.2. The pores are arranged periodically along three orthogonal axes.

[0085] The walls 30 are hollow, i.e. there are cavities traversing the entire thickness of the walls, providing a fluid link with adjacent cellular pores.

[0086] As shown in the enlarged photograph of a wall 30, a wall 30 contains parietal pores 31 that are delimited by dense metal zones 32.

[0087] The part therefore has a cell porosity determined by the cellular pores and a parietal porosity determined by the parietal pores.

[0088] FIG. 2 shows different examples of basic patterns 50 that form a porous structure by periodic repetition. Naturally, basic patterns other than those shown can be used to form a porous structure.

[0089] The basic patterns are for example a lattice, which can be based on a cube, octahedron, dodecahedron, octagonal gyrobicupola, cuboctahedron, truncated octahedron, great icosahedron or icosahedron.

[0090] A cellular pore can be delimited by a basic pattern, for example a cube 51 or an octahedron 52. Such a cellular pore 20 is then delimited by a wall 30 with several faces, each face having a through-cavity 53. The wall of such a cellular pore then has a polyhedral lattice form.

[0091] In a variant, a cellular pore can be delimited by repeating the basic pattern in at least one direction, as is for example the case of the star-shaped basic pattern shown in FIG. 2.

[0092] FIG. 3A shows the trajectory of a laser beam 100 during manufacture of a porous structure by laser additive manufacturing on a powder bed. The spot of the laser beam is moved along the displacement vectors spaced apart by a shift value HD on a powder bed 110 of thickness e to be fused, deposited on previously deposited layers and bound together 120 by the laser beam. As shown in FIGS. 3B and 3C, the zones impacted, and therefore partially fused, by the laser beam extend through the entire thickness of the layer to be fused, as well as through a portion of the lower layer on which the layer being fused rests. The zones impacted by the laser beam during movement thereof can be non-overlapping (FIG. 3B) or partially overlapping (FIG. 3C). A shift value HD can therefore prevent partial overlapping of the impacted zones and facilitate the formation of parietal porosity. Furthermore, a high movement speed of the laser spot causes lower local heating of the zone impacted by the laser beam, which facilitates the formation of parietal porosity.

EXAMPLES

Example 1

[0093] The part illustrated in FIG. 1 was manufactured as follows:

[0094] A powder of particles of 316L stainless steel with a median diameter D50 of 36 .Math.m was used in a LPBF additive manufacturing machine sold by SLM Solutions. The machine is fitted with a laser source emitting a wavelength of 1040 nm.

[0095] The part was manufactured with the additive manufacturing machine on a manufacturing plate made of 316L stainless steel heated to a temperature of 200° C. with the following parameters: [0096] layer thickness: 30 .Math.m, [0097] laser power: 225 W, [0098] movement speed of the laser beam: 4771 mm/s, [0099] shift value: 100 .Math.m, [0100] energy density of the laser beam: 15.71 J/mm.sup.3.

[0101] These specific operating parameters result in a porous structure with a specific parietal porosity.

Example 2

[0102] A 316L stainless steel powder with a median diameter D50 of 36 .Math.m was used in an LPBF machine sold by SLM Solutions. The machine is fitted with a laser source emitting a wavelength of 1040 nm.

[0103] The part was manufactured with the additive manufacturing machine on a manufacturing plate made of 316L stainless steel heated to a temperature of 200° C. with the following parameters: [0104] layer thickness: 50 .Math.m, [0105] laser power: 275 W, [0106] movement speed of the laser beam: 3501 mm/s, [0107] shift value: 120 .Math.m.

[0108] The energy density of the laser beam is less than the threshold energy density. The porous structure has a cell porosity of 85% and the metal walls thereof have a parietal porosity of 35.7%, measured by using optical microscopy and image processing. The total porosity of the part is therefore 94.6%.

[0109] Naturally, the invention is not limited to the example embodiments of the part and the example implementations of the method described by way of non-limiting example.

[0110] For example, the part according to the invention is a heat exchanger, a filtering member or a structural part. Such a part can therefore be used in the healthcare, mining or construction sectors.