Metal powder deposition nozzle

Abstract

The invention refers to a metal powder deposition nozzle comprising: an outer body and an inner body co-axially assembled with the outer body, such that a frusto-conical section of the inner body is placed inside a frusto-conical wall of the outer body. A passageway is formed in between the frusto-conical section and the frusto-conical wall for the passage of a flow of metal powder. An annular channel is formed in between a cylindrical outer surface of the inner body and a cylindrical inner surface of a flange of the outer body, wherein the annular channel fluidly communicates flow distribution channels with the passageway. The separation distance in a radial direction between the cylindrical outer surface of the inner body and the cylindrical inner surface of the flange of the outer body, is larger than the diameter of each one of the flow distribution channels.

Description

[0001] METAL POWDER DEPOSITION NOZZLE

[0002] DESCRIPTION

[0003] TECHNICAL FIELD

[0004] The present invention relates in general to laser metal deposition technology.

[0005] An object of the invention is the provision of a metal powder deposition nozzle for a laser head, that improves performance of a laser metal deposition process.

[0006] In particular, the invention provides a metal powder deposition nozzle that reduces metal powder clogging and that facilitates cleaning and maintenance.

[0007] STATE OF THE ART

[0008] Laser metal deposition is an additive manufacturing technology in which metal objects are built up on a substrate. A particular case of additive manufacturing is laser cladding, wherein metal layers are applied to existing components, for strengthening, modifying or repairing a surface of a metal component.

[0009] During a laser metal deposition process, metal powder is projected through a nozzle coupled to a laser head using a carrier gas, and a laser beam melts the metal powder to generate a melt pool on an existing surface. The melted powder bonds with the base material in the melt pool, thereby forming additively new layers or objects.

[0010] In conventional nozzles, as the one shown in Figure 5A powder flows through powder flow distribution channels (14) and through an interspace (15) between a nozzle conical outer part (16) and a nozzle conical inner part (17), and since those channels are small and typically have triangular corners and recessed areas, powder clogs (18) are easily formed in the corners creating and obstacle for the flow of powder, which alters the lineal trajectory of the particles and reduces velocity of the flow of power, hence, the flow becomes turbulent in the interspace (15) as indicated by the wavy arrow in Figure 5A.

[0011] As a result of the above and as represented in Figure 5B, the shape of the cone of metal powder (19) discharged out of the nozzle, is uneven and a large number of particles are dispersed out of the cone as indicated by the wavy arrow in Figure 5B. The result of this, the particles of metal power do not converge properly at the apex of the cone, thus, the melt pool (20) cannot be formed accurately throughout a manufacturing process. Consequently, the laser deposition process is not efficient because a large amount of metal particles are wasted, and the quality of the process is not as desired.

[0012] Furthermore, maintenance of laser heads is often time-consuming due to the complexity of disassembly the nozzle to clean out powder, mainly due to the formation of metal powder depositions and due to the difficulty in disassembly the two parts of the nozzle as vacuum often is formed between the two parts.

[0013] Moreover, since the nozzle may determine the powder focus, which should correspond to a laser spot size, it is often necessary to change nozzles to alter the powder focus and thereby the processing area. However, traditional nozzle designs are generally not conceived for easy nozzle changes.

[0014] Therefore, there is a need for metal powder deposition nozzles which address the aforementioned shortcomings.

[0015] DESCRIPTION OF THE INVENTION

[0016] The invention is defined in the attached independent claims and satisfactorily solves the above-described drawbacks of the prior art, by the provision of a metal powder deposition nozzle, adapted to be coupled to a laser head to be used in a laser metal deposition process.

[0017] The nozzle comprises an outer part formed as a unitary body having a frusto-conical wall and a peripheral flange which extends around the wider part the frusto-conical wall. This flange has a cylindrical inner surface coaxial with the nozzle's axis.

[0018] The nozzle also comprises an inner part also formed as a unitary body having: a cylindrical section defining a cylindrical outer surface, a frusto-conical section and an internal axial duct for conducting a laser beam through the inner body. The inner body is co-axially assembled with the outer body, in a way that the frusto-conical section is placed inside the frusto-conical wall of the outer body, and a passageway is formed in between the frusto-conical section and the frusto-conical wall for the passage of a flow of metal powder formed by metal powder and a carrier gas. Metal powder flows through the passageway, and converges towards the laser beam at the outlet of the nozzle. The inner body has a plurality of individual powder flow distribution channels, preferably six distribution channels, which are preferably I arched in shape and are circumferentially arranged around the axis of the nozzle. Each one of these flow distribution conduits, is an arch of a circumference having as center the axis of the nozzle.

[0019] An annular chamber is formed in between the cylindrical outer surface of the inner body and the cylindrical inner surface of the flange of the outer body, so that a cross-sectional view of this annular chamber, taken at a plane which includes the nozzle's axis, has a rectangular area. This configuration of the annular chamber facilitates the flow of power without reducing its velocity, so that instead of a turbulent flow, a laminar flow of metal powder is achieved.

[0020] This annular chamber fluidly communicates the flow distribution channels with the passageway, so that metal powder supplied by a feeder is introduced into the nozzle, would circulate first through the individual powder flow distribution channels, then through the annular chamber and from there through the passageway until it flows out of the nozzle through the nozzle's outlet. That is, the annular chamber is placed right upstream the interspace between inner and outer bodies.

[0021] The separation distance in a radial direction between the cylindrical outer surface of the inner body and the cylindrical inner surface of the flange of the outer body, is larger than the diameter of each one of the flow distribution channels. This means that the annular chamber is an expansion or enlargement of the cross-sectional area through which the metal powder flows.

[0022] The annular chamber is free of triangular corners or recessed areas, which avoids the formation of metal powder clogs.

[0023] Preferably, the outer surface of the frusto-conical section of the inner body and the inner surface of the outer body, are substantially smooth curved surfaces, that is, there are no ridges or grooves formed on those surfaces, such that a cross-sectional area of the passageway, taken at a plane orthogonal to the nozzle's axis, is constant and it has the shape of a ring.

[0024] The inner body also has a flange and the nozzle is configured such that when the inner and outer bodies are operatively assembled together, the flange of the inner body overlaps with the flange of the outer body for the attachment of the two bodies. Conventionally, the two flanges are provided with bore holes for the attachment of the two bodies, for example by means of screws. The contacting surface between the two flanges, is formed with a chamfer. For forming this chamfer, the flange of the outer body has a tapered annular surface, and the flange of the inner body also has annular tapered surface complementary to the tapered surface of the outer body, so when the two bodies are assembled together, both tapered surfaces overlap defining a contacting surface between the two flanges which is tapered towards the nozzle's outlet.

[0025] The interspace of the chamfer between the inner and outer bodies, communicates with the annular chamber, or in other words, the interspace of the chamfer between the inner and outer bodies, extends from the annular chamber.

[0026] The provision of a chamfer between the two flanges as described above, prevent the formation of vacuum between the inner and outer bodies, which in turn facilitates disassembly between the inner and outer bodies. In this way, the maintenance and cleaning tasks of a nozzle, are greatly simplified.

[0027] BRIEF DESCRIPTION OF THE DRAWINGS

[0028] To complete the description and in order to provide a better understanding of the invention, a set of drawings is provided. These drawings form an integral part of the description and illustrate embodiments of the invention, which should not be interpreted as restricting the scope of the invention, but just as examples of how the invention can be carried out. The drawings comprise the following figures:

[0029] Figure 1 .- shows a preferred embodiment of a nozzle according to the invention, Figure 1 A is a front elevational view, Figure 1 B is a bottom plant view, Figure 1C is a top plan view, and Figure 1 D is a cross-sectional view taken at plane A-A in Figure 1 A.

[0030] Figure 2.- shows a cross-section la view of the nozzle of the previous figure with the two nozzle bodies disassembled.

[0031] Figure 3.- shows a cross-sectional view in perspective, of the same nozzle.

[0032] Figure 4.- shows a similar representation than Figure 3 but with the two nozzle bodies disassembled. Figure 5.- shows in Figure 5A an enlarged detail of the conventional design of a metal powder distribution chamber according to the prior art, wherein the turbulent trajectory of metal powder is represented by an arrow. Figure 5B is a representation of the metal powder cone formed by the ejected powder flowing out of the nozzle of Figure 5A, wherein the arrows indicate the particles dispersion caused by the turbulent flow of particles through the nozzle of Figure 5A.

[0033] Figure 6.- shows in Figure 6A an enlarged detail of the metal powder distribution chamber according to the present invention, wherein the laminar and uniform trajectory of metal powder is represented by an arrow. Figure 6B is a representation of the metal powder cone formed by the ejected powder flowing out of the nozzle of Figure 6A, wherein the arrows indicate the formation of a clean cone of power without particles dispersion.

[0034] PREFERRED EMBODIMENTS OF THE INVENTION

[0035] The enclosed figures show a preferred embodiment of a coaxial nozzle (1) according to the invention for metal powder deposition, which comprises an outer unitary body (2) having a frusto-conical wall (2a) and a peripheral flange (2b) having a cylindrical inner surface (4) coaxial with the nozzle's axis (X), and a tapered annular surface (5) which is continuous with the inner surface (4).

[0036] The nozzle (1) further includes an inner unitary body (3) having: a frusto-conical section (3a), a cylindrical section (3b), a flange (3c) projecting radially from the cylindrical section (3b), and an internal axial duct (6) for conducting a laser beam. The cylindrical section (3b) has a cylindrical outer surface (13).

[0037] Additionally, the flange (3c) of the inner body (3) has several powder flow distribution channels (7), circumferentially arranged around the nozzle's axis (X), as better shown in Figures 1C and 3. Each one of these flow distribution channels (7) has the shape of an arc of a circumference, and in this exemplary embodiment, they are six flow distribution channels (7), so that each channel (7) is the arc of a 60° sector of a circle.

[0038] The flange (3c) has a tapered annular surface (8) at its bottom base (9), which is complementary to the tapered surface (5) of the outer body (2), in the sense that they have the same angle of inclination and orientation with respect to the axis (X), hence, when the inner and outer bodies (2,3) are operatively assembled together, the two tapered annular surfaces (5,8) overlap, as shown for example in Figure 1 D configuring a chamfer (21) which facilitate disassembly of the two bodies. As it can be observed, for example in Figure 1D, the interspace between the inner and outer bodies at the chamfer (21), communicates with the annular chamber (12), or in other words, the interspace between the inner and outer bodies at the chamfer (21) extends from the annular chamber (12).

[0039] The flow distribution channels (7) are located between the tapered annular surface (8) and the cylindrical section (3b) of the inner body (3).

[0040] The inner and outer bodies (2,3) are coaxially assembled together as shown for example in Figure 1 D, such that the frusto-conical section (3a) of the inner body (3) is placed inside the frusto-conical wall (2a) of the outer body (2). A passageway (10) is formed in the interspace between the frusto-conical section and the frusto-conical wall, for the passage of a flow of metal powder, that is, metal powder conveyed by a carrier gas in a known manner.

[0041] The outer surface of the frusto-conical section (3a) of the inner body and the inner surface frusto-conical wall (2a) of the outer body, are substantially smooth curved surfaces, such that any cross-sectional area of the passageway (10), taken at a plane orthogonal to the nozzle's axis (X), has the shape of a ring.

[0042] Preferably, the outer surface of the frusto-conical section (3a) of the inner body and the inner surface frusto-conical wall (2a) of the outer body, have a highly-polished shiny finish, to facilitate circulation of the flow of powder.

[0043] The flange (3c) of the inner body (3) is placed on top of the flange (2b) of the outer part (2) and the two flanges are provided with bore holes (11 ,11 ') for the attachment of the two bodies, for example by means of screws (not shown) which also serve to attach the nozzle to a laser head (not shown).

[0044] An annular chamber (12) is formed in between a cylindrical outer surface (13) of the cylindrical section (3b) of the inner part (3), and the cylindrical inner surface (4) of the flange (2b) of the outer body (2). This annular chamber (12) fluidly communicates all flow distribution channels (7) with the passageway (10).

[0045] The separation distance in a radial direction with respect to axis (X), between the cylindrical outer surface (13) of the inner body (3) and the cylindrical inner surface (4) of the flange (2b) of the outer body (2), is constant and larger than the width of each one of the flow distribution channels (7) as it can be noted for example in Figure 1 D.

[0046] In this way, the annular chamber (12) placed right downstream the flow distribution channels (7), enlarges the cross-sectional area through which the metal powder flows, compared with the sum of all cross-sectional areas of the flow distribution channels (7). This configuration of the annular chamber (12) as a straight passage, without acute triangular corners or recessed areas, avoids formation of obstacles caused by metal powder clogs.

[0047] This advantage of the invention is represented in Figure 6A, where it can be observed that the flow of metal powder is laminar through the annular chamber (12) and passageway (10) (represented by the straight arrows in that figure), and as results of that, the cone (19) formed by the ejected particles out of the nozzle (Figure 6B), is well defined and a large amount of the ejected particles converge or are concentrated at the melt pool (20). Thus, in contrast to prior art process illustrated in Figures 5A & 5B, the nozzle of the invention provides an efficient and accurate laser deposition process throughout a manufacturing process.

[0048] The cylindrical outer surface (13) of the inner body (3) is higher than the cylindrical inner surface (5) of the flange (2b) of the outer body (2). The annular chamber (12) in a cross- sectional view as the one shown in Figure 1 D, is rectangular in an upper part and triangular in a lower part which directly communicates with the passageway (10). The annular chamber (12) has two 90° corners at its upper part which directly communicate with the flow distribution channels (7).

[0049] Preferably, for Laser Metal Deposition (LMD) applications, the frusto-conical wall (2a) of the outer body and the frusto-conical section (3a) of the inner body, define an angle of around 40° with respect to the nozzle's axis (X).

[0050] Alternatively, for Ultra-High Speed Laser Cladding (EHLA) applications, the frusto-conical wall (2a) of the outer body and the frusto-conical section (3a) of the inner body, define an angle equal or larger than 45° with respect to the nozzle's axis (X), preferably this angle is within the range 60° - 100°.

Claims

CLAIMS1.- Metal powder deposition nozzle (1), comprising: an outer body (2) having a frusto-conical wall (2a) and a peripheral flange (2b) having a cylindrical inner surface (4) coaxial with the nozzle's axis (X), an inner body (3) having: a cylindrical outer surface (13), a frusto-conical section (3a) and an internal axial duct (6) for conducting a laser beam, wherein the inner body (3) is co-axially assembled with the outer body (2), such that the frusto- conical section (3a) is placed inside the frusto-conical wall (2a) of the outer body (2), and a passageway (10) is formed in between the frusto-conical section (3a) and the frusto-conical wall (2a) for the passage of a flow of metal powder, wherein the inner body (3) has several powder flow distribution channels (7) circumferentially arranged around the nozzle's axis (X), wherein an annular chamber (12) is formed in between the cylindrical outer surface (13) of the inner body (3) and the cylindrical inner surface (4) of the flange (2b) of the outer body (2), wherein the annular chamber (12) fluidly communicates the flow distribution channels (7) with the passageway (10), and wherein the separation distance in a radial direction between the cylindrical outer surface (13) of the inner body (3) and the cylindrical inner surface (4) of the flange (2b) of the outer body (2), is larger than the diameter of each one of the flow distribution channels (7).2.- Metal powder deposition nozzle according to claim 1 , wherein the outer surface of the frusto-conical section of the inner body (3) and the inner surface of the frusto-conical wall (2a) of the outer body (2), are substantially smooth curved surfaces, such that a cross-sectional area of the passageway (10), taken at a plane orthogonal to the nozzle's axis, has the shape of a ring.3.- Metal powder deposition nozzle according to claim 1 or 2, wherein the cylindrical outer surface (13) of the inner body (3) is higher than the cylindrical inner surface (4) of the flange (2b) of the outer body (2).4.- Metal powder deposition nozzle according to any of the preceding claims, wherein the inner body (3) has a flange (3c), and wherein the nozzle (1) is configured such that when the outer and inner bodies (2,3) are operatively assembled together, the flange (3c) of the inner body overlaps with the flange (2b) of the outer body for the attachment of the two bodies.5.- Metal powder deposition nozzle according to claim 4, wherein a part of the contactingsurface between the flanges (2b, 3b) of the inner and outer bodies, is tapered towards the nozzle's outlet (14) configuring a chamfer (21).6.- Metal power deposition nozzle according to claim 5, wherein the interspace between the inner and outer bodies (2,3) at the chamfer (21), extends from the annular chamber (12).7.- Metal powder deposition nozzle according to any of the preceding claims, wherein each of the flow distribution channels (7) has the shape of an arc of a circumference.8.- Metal powder deposition nozzle according to any of the preceding claims, wherein the frusto-conical wall (2a) of the outer body (2) and the frusto-conical section (3a) of the inner body (3), define an angle of around 40° with respect to the nozzle's axis.9.- Metal powder deposition nozzle according to any of the claims 1 to 5, wherein the frusto- conical wall (2a) of the outer body and the frusto-conical section (3a) of the inner body, define an angle equal or larger than 45° with respect to the nozzle's axis.10.- Metal powder deposition nozzle according to claim 9, wherein the angle is within the range 60° - 100°.11 .- A laser head adapted for a laser metal deposition process, incorporating the metal powder deposition nozzle defined in any of the preceding claims.

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