Thermal spray deposition method, and thermal spray deposition apparatus

Abstract

A thermal spray deposition method for additive manufacturing is provided. The method comprises the steps of: arranging a deposition nozzle (1302) for depositing a material onto a substrate (1312); arranging a flow separator (1310), relative to the substrate (1312) and the deposition nozzle (1302), so that the flow separator (1310) is positioned to split a flow of material emanating from the deposition nozzle (1302), and to allow material deposited on the substrate (1312) to form a structure conforming to a surface of the flow separator (1310); and spraying a flow of material through the deposition nozzle (1302) to deposit the material on the substrate (1312) to form a structure conforming to the surface of the flow separator (1310). The flow separator (1310) is positionably-securable independently of any edge of the substrate. A thermal spray deposition apparatus (1300) is also provided.

Description

[0001] Thermal Spray Deposition Method, and Thermal Spray Deposition Apparatus

[0002] Technical field

[0003] The disclosure relates to a thermal spray deposition method in which a flow separator is arranged, positionably-securable independently of any edge of a substrate onto which a deposition nozzle is arranged to deposit a material to form a structure conforming to a surface of the flow separator. The disclosure also relates to a thermal spray deposition apparatus.

[0004] Background

[0005] Additive manufacturing (AM), sometimes referred to as 3D printing, is a process in which a three-dimensional object is built up layer by layer. AM has received growing interest because it promises improved efficiency and design freedom and customisation compared to other manufacturing methods.

[0006] Within the field of AM, metallic additive manufacturing (mAM) is a rapidly growing field, with possible application in sectors such as aerospace, motorsport and medical implants. However, mAM has been limited by the achievable build rate. Powder bed AM is limited by a variety of factors, such as maximum layer depth, melt pool scan speed and powder distribution rate. On the other hand, in blown powder AM the deposited material must be melted, limiting deposition rates. The deposition rates must be limited to avoid excessive residual stresses in manufactured objects. Blown powder AM is also limited in “precursor” material choice and objects manufactured using blown powder AM often require post process machining and heat treatment.

[0007] Thermal spraying processes are coating processes in which heated or melted precursor material is sprayed onto a surface to coat the surface. Thermal spraying processes may use a variety of materials, including metals, alloys, ceramics, polymers, and composites, and allow for high deposition rates.

[0008] Cold spray (CS) deposition is a known thermal spray coating process in which powder is deposited by entraining powder particles in a heated and compressed propulsive gas. The powder particles are accelerated to high velocities (typically >300 m / s) through a converging diverging (de Laval) nozzle. After particles exit the nozzle, they impact a substrate - if the velocity of the particle is greater than a, material-dependent, critical velocity (Vcrit), the particle deposits on the substrate. However, there is typically no, or limited, control over the shaping of a deposit from CS deposition, leading to waste and increased time and cost of CS deposition.

[0009] The inventors have appreciated the need for an improved method for additive manufacturing, in particular a method of additive manufacturing with increased deposition rates compared to powder bed additive manufacturing and blown powder additive manufacturing.

[0010] Summary of the Disclosure

[0011] The disclosure provides a thermal spray deposition method for additive manufacturing, and a thermal spray deposition apparatus for additive manufacturing, as defined in the appended independent claims, to which reference should now be made. Optional or advantageous features of the disclosure are set out in dependent subclaims.

[0012] According to a first aspect of the disclosure, there is provided a thermal spray deposition method for additive manufacturing. The method comprises the steps of: arranging a deposition nozzle for depositing a material onto a substrate; arranging a flow separator, relative to the substrate and the deposition nozzle, so that the flow separator is positioned to split a flow of material emanating from the deposition nozzle, and to allow material deposited on the substrate to form a structure conforming to a surface of the flow separator, wherein the flow separator is positionably-securable independently of any edge of the substrate; and spraying a flow of material through the deposition nozzle to deposit the material on the substrate to form a structure conforming to the surface of the flow separator.

[0013] The inventors have found that by arranging a flow separator to split a flow of material and to allow material deposited on the substrate to form a structure conforming to a surface of the flow separator, the high deposition rate thermal spay deposition method of the first aspect may allow for additive manufacturing of a three-dimensional object, and in particular of vertical walls with a low surface roughness, at a high rate.

[0014] The inventors have further found that by providing a flow separator which is positionably- securable independently of any edge of the substrate, the method of the first aspect is not limited to creating a three-dimensional structure, such as a vertical wall, at, or near, the edge of the substrate, allowing for flexibility. In other words, a flow separator being positionably- securable independently of the edge of the substrate may allow for a three-dimensional structure to be manufactured at any location on the substrate. The term “positionably-securable” may be understood to mean that the flow separator may be secured independently of any edge of the substrate, so as to allow the flow separator to be positionable independently of any edge of the substrate. The flow separator may be mounted in such a way that movement relative to the substrate is prevented.

[0015] The structure may alternatively be referred to as a deposited structure, or a deposit, or an object, or a component. As used herein, the term “structure” may refer to a three- dimensional deposit, or object, or component, made up of, or built up of, deposited material, in particular, built up of layers of material.

[0016] The inventors have further found that by providing a flow separator which is positionably- securable independently of any edge of the substrate, rather than a flow separator which is secured to an edge of the substrate, a three-dimensional structure having at least one angled wall may be produced by angling the flow separator (relative to the substrate).

[0017] As used herein, the term “a structure conforming to a surface of the flow separator” may refer to one side, or one surface, of the deposit, or deposited structure, conforming to a surface of the flow separator. In particular, it may refer to a surface of the deposit, or structure, adjacent the flow separator conforming to the adjacent surface of the flow separator.

[0018] The term “a structure conforming to a surface of the flow separator” may refer to at least one side, or at least one surface, of the deposited structure conforming to, e.g. a shape and / or an angle of, a surface of an adjacent flow separator. For example, if the (surface of the) flow separator is arranged at an angle relative to the substrate, an angle of said (conforming) surface of the structure may conform to the angle of (the surface of) the flow separator.

[0019] In other words, the deposited structure may conform to a surface of the flow separator because it is formed by building up a deposit against the flow separator. That is, the deposited structure may be directly impacted by the presence of the flow separator since it is built against (a surface of) the flow separator. This may differ from known processes in which a mask is used to affect a deposit, in which the deposit is not built up against, or in direct contact with, the mask.

[0020] The thermal spray deposition method of the first aspect may be a plasma spray deposition method for additive manufacturing. Alternatively, the thermal spray deposition method of the first aspect may be a high velocity oxygen fuel HVOF coating method for additive manufacturing. Further alternatively, the thermal spray deposition method of the first aspect may be a detonation spraying, or D-gun spraying, method. The thermal spray deposition method of the first aspect may be a cold spray deposition method for additive manufacturing. Contrary to other thermal spray deposition methods, cold spray deposition is a solid-state deposition method, that is, the precursor material / powder is not melted at any point during the deposition process. Thus, advantageously, a microstructure of the precursor material / powder may be maintained. A cold spay deposition method may also allow for temperature sensitive materials to be deposited.

[0021] In examples in which the method of the first aspect is a cold spray deposition method, by arranging a flow separator as set out above, improved control over the shaping of the deposit may be achieved, thus enabling cold spray deposition to be used for additive manufacturing. Because cold spray deposition does not involve melting, three-dimensional structures created using cold spray deposition may exhibit less residual stress than three- dimensional structures created using other thermal spray deposition methods.

[0022] Optionally, the cold spray deposition method may be a laser-assisted cold spray deposition method. The laser-assisted cold spray deposition method may alternatively be referred to as a “supersonic laser deposition method”. The laser-assisted cold spray deposition method may further comprise the step of heating a deposition zone to between about 30% and 80% of precursor particle melting point. This may allow for required impact velocities to be reduced relative to other cold spray deposition methods by up to 50%. Advantageously, the laser-assisted cold spray deposition method for additive manufacturing may thus permit reduced gas (typically nitrogen) usage and thus reduced operating costs.

[0023] Where the method is a cold spray deposition method, or a supersonic laser deposition method, high deposition rates (e.g. > 8 kg per hr) may be achieved, which may exceed deposition rates of established mAM processes.

[0024] In the method according to the present disclosure, the underlying mechanism enabling conformal and smooth deposit formation may be that the deformation of particles due to impact is constrained by the flow separator. The result may be a deposit having a conforming surface which may be up to an order of magnitude smoother (Ra < 5 pm) than that of a typical cold spray deposit where the deformation is unconstrained (Ra > 20 pm).

[0025] In order to be deposited, the particles must remain above their critical deposition velocity as they travel through the shock structures produced by interaction with the supersonic flow and the flow separator before impacting the substrate. The inventors have found that the method of the first aspect may be a significant advancement over alternative deposit shaping techniques such as spraying through a mask or over a wide step where the height over which conformal wall building can be achieved is very small (1-2 mm) and inconsistent.

[0026] Optionally, the flow separator is positionably-securable independently of the substrate. By providing a flow separator which is positionably-securable independently of the substrate, yet greater flexibility in the shape of the three-dimensional structure being manufactured may be achieved. Indeed, the flow separator being positionably-securable independently of the substrate allows manufacturing of various open and closed contour shapes.

[0027] It is noted that although the flow separator may be positionably-securable independently of the substrate, arranging the flow separator relative to the substrate may still comprise arranging the flow separator so that it contacts the substrate, i.e. so that there is no gap between a first (lower) edge of the flow separator and the (top surface of the) substrate. In some examples, arranging the flow separator relative to the substrate may comprise arranging the flow separator so that it does not contact the substrate, i.e. so that there is a gap between a first (lower) edge of the flow separator and the substrate.

[0028] The flow separator may be positionably-securable by fastening and / or clamping, e.g., to a support structure, or to the deposition nozzle.

[0029] The support structure may be secured independently of the substrate, thus the flow separator being securable independently of the substrate.

[0030] The flow separator may be attached to the support structure to permit positioning of the flow separator in at least two dimensions. The flow separator may be rotated. For example, the flow separator may be rotated about at least one of: a normal of the flow separator, a first axis of the flow separator, or a second axis of the flow separator.

[0031] Optionally, arranging the deposition nozzle and arranging the flow separator may comprise arranging the deposition nozzle and the flow separator so that a centreline of the deposition nozzle is offset from a deposition-side distal corner of the flow separator, in a direction of a deposition zone, by about 0.1 PD to about 10 PD, wherein PD is a mean particle diameter of particles in the material.

[0032] As used herein, the term “distal” may refer to portions of the flow separator which are closer to the substrate, whereas the term “proximal” may refer to portions of the flow separator which are closer to the deposition nozzle.

[0033] As used herein, “mean particle diameter”, or PD, is a mean diameter of particles in the precursor material / powder. In particular, the PD of the powder may be a mean particle diameter D50 as determined according to ISO 13320:2009. The PD may be measured using a laser diffraction particle size analyser such as a Malvern Panalytical Mastersizer 3000, which is designed to meet the requirements of ISO 13320:2009.

[0034] It is noted that if precursor powders are purchased, the PD will typically be provided by the supplier of the precursor powder. The PD may be described by the supplier as the mean particle diameter, or as D50.

[0035] Optionally, the centreline of the deposition nozzle is offset by about 0.5 PD to about 5 PD, or by about 1 PD to about 2 PD. The inventors have found that deposition efficiency is maximised whenever the centreline of the deposition nozzle is about 1 PD to about 2 PD away (on the deposition side) from the distal deposition-side corner of the flow separator.

[0036] In one particular example in which precursor material is a copper powder having a mean particle diameter of 30 pm, if the centreline of the deposition nozzle is offset by about 1 PD to about 2 PD, the centreline of the deposition nozzle may be offset by about 30 pm to about 60 pm.

[0037] Optionally, arranging the deposition nozzle and arranging the flow separator may comprise arranging the deposition nozzle and the flow separator so that a centreline of the deposition nozzle is offset from a deposition-side distal corner of the flow separator, in a direction of a deposition zone, by about 0.1 pm to about 1000 pm, optionally by about 1 pm to about 200 pm, optionally by about 20 pm to about 80 pm, further optionally by about 38 pm to about 76pm.

[0038] Arranging the flow separator, relative to the substrate and the deposition nozzle, may comprise arranging the flow separator so that a proximal end of the flow separator and a centreline of the deposition nozzle are offset by a distance RX.

[0039] The flow separator may be offset by the distance RX toward a deposition zone. In particular, RX may be about 0.001 NFD to about 0.125 NFD, wherein NFD is a nozzle footprint diameter of the deposition nozzle. Optionally, RX may be about 0.01 NFD to about 0.1 NFD.

[0040] The nozzle footprint diameter, or NFD, is the diameter of the nozzle footprint, wherein the nozzle footprint is the area in which particles are deposited on the substrate. It depends on various parameters, such as nozzle diameter, nozzle to substrate distance, etc. The NFD may be determined experimentally for a given setup by depositing a single line of material and measuring its width. Alternatively, the flow separator may be offset by the distance RX away from the deposition zone. In particular, RX may be about 0.001 NFD to about 0.75 NFD, wherein NFD is a nozzle footprint diameter of the deposition nozzle. Optionally, RX is about 0.1 NFD to about 0.5 NFD.

[0041] The term “deposition zone” may refer to an area, adjacent one side of the flow separator, in which the material is being deposited. In the thermal spray deposition method of the first aspect, the three-dimensional structure is deposited conforming to the surface of the flow separator, i.e. a surface of the flow separator on one side of the flow separator. The area adjacent the flow separator in which the material is being deposited to build up the three- dimensional structure may be referred to as the “deposition zone”.

[0042] It will be understood that instead of referring to a “deposition zone”, one side of the flow separator may be referred to as a deposition side, and the other side of the flow separator may be referred to as an averted side. As such, a direction “toward a deposition zone” may be alternatively referred to as being a deposition side direction, and a direction “away from a deposition side” may be referred to as being an averted side direction. It is noted that whether the directions are referred to as directions toward and away from a deposition zone, or a deposition side direction and an averted side direction, these direction are opposing directions.

[0043] The flow separator may comprise a stiffening portion, and a splitting portion for splitting the flow of material, coupled to the stiffening portion. Advantageously, by providing a splitting portion for splitting the flow of material, coupled to a stiffening portion, the flow separator may have a higher stiffness, which may reduce deflection during deposition. Reduced deflection may result in less trench formation and higher deposition rates and uniformity. Further advantageously, such a flow separator may more easily be positionably-secured without affecting the properties of splitting the flow.

[0044] A trench is a gap between the peak of the deposited structure and the flow separator FS.

[0045] Optionally, arranging the flow separator may comprise securing, optionally clamping or fastening, the flow separator.

[0046] Securing the flow separator may comprise laterally securing and / or vertically securing the flow separator.

[0047] The terms “lateral” and “vertical” are used for descriptive purposes only, and may refer to the direction of the securing, or clamping, force when the flow separator is positioned for use. That is, “lateral” may refer to portions on which a clamping force acts in a lateral direction, that is, in a direction which is substantially parallel to a plane of the substrate when the flow separator is positioned for use, and along a first dimension of the flow separator. The lateral securing portions may be besides the splitting portion when positioned for use. “Vertical” may refer to portions on which a clamping force acts in a vertical direction, that is, in a direction which is substantially towards the substrate when the flow separator is positioned for use, and along a second dimension of the flow separator. In other words, vertical securing portions may typically be proximal (above) the splitting portion when the flow separator is positioned for use.

[0048] Securing the flow separator may comprise clamping or fastening the flow separator at a plurality of securing portions on the stiffening portion. Optionally, securing the flow separator may comprise clamping or fastening the flow separator at two, or three, securing portions. Further optionally, the plurality of securing portions is disposed about different edges of the flow separator.

[0049] Further optionally, the plurality of securing portions comprises at least two lateral securing portions, and at least one vertical securing portion.

[0050] Arranging the flow separator may comprise arranging the flow separator to be in contact with the substrate. Alternatively, arranging the flow separator may comprise arranging the flow separator to be separated from the substrate.

[0051] For example, if securing the flow separator comprises vertically clamping the flow separator, the flow separator may be in contact with the substrate to create the vertical clamping force.

[0052] In some examples in which the flow separator is secured to a support structure and / or the deposition nozzle, arranging the flow separator comprises arranging the flow separator to be in contact with the substrate. In alternative examples in which the flow separator is secured to a support structure and / or the deposition nozzle, arranging the flow separator comprises arranging the flow separator to be separated from the substrate by a gap.

[0053] In examples in which the flow separator comprises the stiffening portion, the stiffening portion may be a supporting step coupled to one side of the splitting portion.

[0054] The inventors have found that coupling such a supporting step to the splitting portion increases a stiffness of the flow separator. Indeed, by coupling, in particular brazing, a supporting step to an averted side of the splitting portion, the supporting step may also serve as a shield for the substrate, preventing deposits building up on the averted side of the flow separator.

[0055] A height of the flow separator supporting step, that is a distance from the top of the step to the top of the flow separator, may be about 0 mm to about 25 mm, optionally about 10 mm to about 25 mm.

[0056] A width of the flow separator supporting step may be about 0 mm to about 20 mm, optionally about 5 mm to about 20 mm.

[0057] Optionally, securing the flow separator comprises securing the flow separator to the deposition nozzle. Advantageously, this may allow a relative alignment of the flow separator and the deposition nozzle to be more easily controlled and retained. Closely controlling the relative alignment of the flow separator and the deposition nozzle may facilitate consistent deposition results.

[0058] Optionally, a stiffness of the flow separator is such that a maximum deflection 5 of the flow separator during deposition is less than 3 mm. Further optionally, 5 may be less than 70 pm.

[0059] In some embodiments, a height h of the flow separator may be up to about 40 mm. For example, the height h of the flow separator may be about 10 mm to about 40 mm, optionally about 16 mm to about 26 mm, and in particular about 19 mm.

[0060] A thickness t of the flow separator may be about 0.1 mm to about 12 mm, optionally about 0.4 mm to about 5 mm, further optionally about 0.41 mm, or about 0.7 mm.

[0061] It is noted that where the flow separator comprise a splitting portion and a stiffening portion, the flow separator height h and flow separator thickness t may relate to a height and thickness of the splitting portion.

[0062] A deposition side surface of the flow separator to which the deposited structure is configured to conform may have a surface roughness of less than 10 pm, optionally less than 5 pm, further optionally less than 1 pm. Advantageously, the deposition side surface having a surface roughness of 1 pm may facilitate the deposit having a low surface roughness, avoiding any need for surface finishing of the deposited structure.

[0063] Surface roughness may be measured according to ISO 4288, for example using a Alicona InfiniteFocusSL. InfiniteFocusSL is an optical 3D measurement system. A surface of the deposited structure which conforms to the deposition-side surface of the flow separator may have a surface roughness Ra of less than 5 pm. Advantageously, such a surface roughness Ra is comparable to, or may be better (that is, smoother) than, milled components, eliminating the need for post-deposition finishing.

[0064] In other words, because the deposit is formed against the flow separator, a surface roughness of the deposited structure conforming to a surface of the flow separator may be determined by the roughness of the surface of the flow separator. This may differ from known processes in which a mask is used to affect a deposit, in which the deposit is not built up against, or in direct contact with, the mask, and in which surface roughness of the mask and the deposit may differ significantly (e.g. the mask might be very smooth but the deposit may still be rough).

[0065] The flow separator may comprise, or be made from, a material which is harder than the powder material and sufficiently strong to withstand the heat and / or pressure of the flow of gas and powder (stream of material) without deforming (substantively).

[0066] In some embodiments, the flow separator may comprise, or be made of: titanium, stainless steel, or a ceramic, such as fused quartz.

[0067] In one example, the flow separator may be made of stainless steel 316L. In another example, the flow separator may be made of a material having a similar or greater hardness and Young’s modulus than 316L.

[0068] Additionally or alternatively, the flow separator may comprise at least one strengthening means. The at least one strengthening means may comprise at least one of: a reinforcing element, such as at least one supporting rib; a curvature; and a variable thickness.

[0069] Providing a strengthening means may allow the flow separator to be made from a wider variety of materials, to have a lower thickness, and / or to have a greater height.

[0070] Arranging the flow separator relative to the substrate may comprise angling the flow separator relative to being perpendicular to the substrate by a separator-substrate angle cp. Optionally, (p is about 5° toward a, or the, deposition zone, to about 20° away from a, or the, deposition zone. Further optionally, (p is about 5° to about 15° away from a, or the, deposition zone. Yet further optionally, (p is about 10° away from a, or the, deposition zone. Advantageously, angling the flow separator may allow for improved deposition efficiency.

[0071] Arranging the deposition nozzle may comprise angling the deposition nozzle relative to being perpendicular to the substrate by a nozzle-substrate angle p. Optionally, is about 2° toward a, or the, deposition zone, to about 15° away from a, or the, deposition zone; further optionally p is about 2° to about 10° away from a, or the, deposition zone; yet further optionally is about 5° away from a, or the, deposition zone.

[0072] The deposition nozzle and the flow separator may be arranged at a relative angle RA to one another. Optionally, the relative angle RA between the deposition nozzle and the flow separator may be about 0.01° to about 22°, or about 0.1° to about 20°, or about 0.5° to about 15°, or about 1° to about 10°, or about 2° to about 5°.

[0073] As will be apparent to those skilled in the art, RA is dependent on (p and p.

[0074] If RA is less than 0°, that is the nozzle centreline is angled away from the deposition zone more than the flow separator, the flow separator will cast a shadow over the deposition zone, physically blocking particles from reaching the deposition zone. The inventors have found that this may be the case even if the deposition nozzle is fractionally offset, toward the deposition zone (RX < 0mm), causing trench formation.

[0075] Arranging the flow separator, relative to the substrate and the deposition nozzle, may comprise at least one of: translating the flow separator relative to a x-y plane, the x-y plane being defined by the substrate; translating the flow separator relative to a z direction, the z direction being normal to a, or the, x-y plane defined by the substrate; rotation about a z direction, the z direction being normal to a, or the, x-y plane defined by the substrate; rotation about a first direction defined by a, or the, x-y plane being defined by the substrate; and rotation about a second direction defined by the x-y plane, perpendicular to the first direction.

[0076] The flow separator may thus have up to six degrees of freedom. For ease of reference, rotation about the z direction may be referred to as “yaw”, rotation about a first direction (x direction) defined by the x-y plane may be referred to as “pitch”, and rotation about a second direction (y direction) may be referred to as “roll”. (p may be defined as the angle of the flow separator relative to the z direction. Similarly, p may be defined as the angle of the deposition nozzle (centreline) relative to the z direction.

[0077] It is noted that “translation relative to a x-y plane” and “translation relative to a z direction” may relate to the flow separator being translated, e.g. using linear actuators, or it may relate to the substrate being translated, so that the relative arrangement of the separator and flow separator changes accordingly. The same applies, mutatis mutandis, to rotating. In other words, the substrate may be moved relative to the flow separator, rather than the flow separator being moved relative to the substrate.

[0078] The method may further comprise patterning the material deposited on the substrate.

[0079] Patterning may comprise providing the flow separator, and in particular the surface of the flow separator to which the deposited structure is configured to conform, with a pattern. The pattern may be a regular, or repeating pattern, or it may be a unregular pattern.

[0080] Optionally, the method further comprises providing the substrate.

[0081] The substrate may be a metal substrate. In particular, the substrate may be a flat metal plate.

[0082] In one particular example, the substrate may be an aluminium substrate. In other examples, the substrate may be a steel substrate, or a copper substrate, or a nickel substrate.

[0083] The substrate may have a thickness of about 0.5 mm or more. The substrate may have a thickness of about 0.1 mm to about 50 mm, or about 0.5 mm to about 50 mm, or about 1 mm to about 30 mm, or about 5 mm to about 20 mm, optionally about 12 mm.

[0084] The precursor material may be a metal, or metal alloy, powder. The metal powder may comprise at least one of: copper; stainless steel; aluminium and titanium.

[0085] The precursor material may in particular be a powder having a mean particle diameter (PD), of about 1 pm to about 150 pm.

[0086] A mean particle diameter PD of the precursor material may be about 5 pm to about 100 pm. Optionally, PD may be about 10 pm to about 80 pm, or about 20 pm to about 65 pm, or about 30 pm to about 50 pm.

[0087] In one particular example, the precursor material is a copper powder, and PD is about 30 pm. In another example, the precursor material is a copper powder having a powder size cut of 15 pm and 38 pm. In another particular example, the precursor material is a titanium powder, and PD is about 45 pm. In yet another particular example, the precursor material is a steel (316L) powder, and PD is about 20 pm to about 63 pm.

[0088] Arranging a flow separator relative to the deposition nozzle may comprise arranging the flow separator and the nozzle so that a nozzle standoff distance d is about 0 mm to about 50 mm, optionally 40 mm. The nozzle standoff distance d is defined as a distance between a top face of the flow separator and an outlet of the nozzle.

[0089] The step of spraying a flow of material through the deposition nozzle may comprise moving the nozzle centreline relative to the substrate along the flow separator to deposit material along a line. Moving the nozzle centreline relative to the substrate may comprise moving the deposition nozzle, or moving the substrate, or both.

[0090] The step of spraying a flow of material through the deposition nozzle may comprise performing various passes.

[0091] Performing various passes may comprise moving the nozzle centreline relative to the substrate over the same area a plurality of times.

[0092] Performing various passes may comprise moving the nozzle centreline along the flow separator. Performing various passes may further comprise moving the nozzle centreline away from the flow separator, moving the nozzle centreline along the flow separator in an opposite direction, and moving the nozzle centreline towards the flow separator.

[0093] Alternatively, performing various passes may comprise moving the substrate relative to the nozzle.

[0094] According to a second aspect of the disclosure there is provided a thermal spray deposition apparatus for additive manufacturing, the apparatus comprising: a deposition nozzle for depositing a material onto a substrate; and a flow separator positionably-securable independently of any edge of the substrate, wherein the flow separator is arrangeable, relative to the substrate and the deposition nozzle, to split a flow of material emanating from the deposition nozzle, and to allow material deposited on the substrate to form a structure conforming to a surface of the flow separator.

[0095] The inventors have found that arranging a flow separator to split a flow of material and to allow material deposited on the substrate to form a structure conforming to a surface of the flow separator may allow for additive manufacturing of a three-dimensional object at a high powder deposition rate. The inventors have further found that a flow separator which is positionably-securable independently of any edge of the substrate may permit building up of a three-dimensional structure anywhere on the substrate, not just at, or near, the edge of the substrate

[0096] It is noted that the term “positionably-securable” may be understood to mean that the flow separator may be secured independently of any edge of the substrate, so as to allow the flow separator to be positionable independently of any edge of the substrate.

[0097] The inventors have further found that by having a flow separator which is positionably- securable independently of any edge of the substrate, rather than a flow separator which is securable to an edge of the substrate, a three-dimensional structure having at least one angled wall may be produced by angling the flow separator.

[0098] Optionally, the flow separator is positionably-securable independently of the substrate. By providing a flow separator which is positionably-securable independently of the substrate, yet greater flexibility in the shape of the three-dimensional structure being manufactured may be achieved.

[0099] The apparatus may further comprise a substrate holder for holding the substrate.

[0100] The substrate may be an metal substrate, in particular, the substrate may be a flat metal plate.

[0101] The substrate may have a thickness of about 0.5 mm or more. The substrate may have a thickness of about 0.1 mm to about 50 mm, or about 0.5 mm to about 50 mm, or about 1 mm to about 30 mm, or 5 mm to about 20 mm, optionally about 12 mm.

[0102] The thermal spray deposition apparatus of the second aspect may be a plasma spray deposition apparatus. Alternatively, the thermal spray deposition apparatus of the second aspect may be a high velocity oxygen fuel HVOF coating apparatus. Further alternatively, the thermal spray deposition apparatus of the second aspect may be a detonation spraying, or D-gun spraying, apparatus, which may comprise a detonation gun (D-gun).

[0103] The thermal spray deposition apparatus of the second aspect may be a cold spray deposition apparatus. Contrary to other thermal spray deposition methods, cold spray deposition is a solid-state deposition method, that is, the precursor material is not melted at any point during the deposition process. Thus, advantageously, a microstructure of the precursor powder may be maintained. A cold spay deposition apparatus may also allow for temperature sensitive materials to be deposited. As such, a three-dimensional structure created using a cold spray deposition apparatus may exhibit less residual stress than those created using deposition apparatuses which rely on melting the precursor material.

[0104] The cold spray deposition apparatus optionally comprises a laser, particularly a supersonic laser. Optionally, the laser is configured to heat a deposition zone to between about 30% and 80% of precursor particle melting point. This may allow for required impact velocities to be reduced relative to other cold spray deposition apparatuses by up to 50%.

[0105] Advantageously, the apparatus comprising a laser may thus permit reduced gas (typically nitrogen) usage and thus reduced operating costs.

[0106] The cold spray deposition apparatus comprising the laser may be referred to as a supersonic laser deposition apparatus. The supersonic laser deposition apparatus may alternatively be referred to as a laser-assisted cold spray deposition apparatus.

[0107] Optionally, the apparatus may be configurable so that a centreline of the deposition nozzle is offset from a deposition-side distal corner of the flow separator, in a direction of a deposition zone, by about 0.1 PD to about 10 PD, wherein PD is a mean particle diameter (D50) of particles in the precursor material / the flow of material. Further optionally, the apparatus may be configurable so that the centreline of the deposition nozzle is offset by about 0.5 PD to about 5 PD, or by about 1 PD to about 2 PD.

[0108] The apparatus may be configurable so that a proximal end of the flow separator and a centreline of the deposition nozzle are offset by a distance RX. NFD may be a nozzle footprint diameter of the deposition nozzle.

[0109] Optionally, the apparatus may be configurable so that the centreline of the deposition nozzle is offset by RX toward a deposition zone. Further optionally, RX is about 0.125 NFD to about 0.001 NFD, further optionally RX is about 0.1 NFD to about 0.01 NFD. Alternatively, the apparatus may be configurable so that the centreline of the deposition nozzle is offset by RX away from the deposition zone. Further alternatively, RX is about 0.001 NFD to about 0.75 NFD, optionally RX is about 0.1 NFD to about 0.5 NFD.

[0110] The flow separator may comprises a stiffening portion, and a splitting portion coupled to the stiffening portion. The splitting portion may refer to a portion of the flow separator configured to split the flow, and to a surface to which the structure conforms, whereas the stiffening portion may be a portion of the flow separator configured to stiffen the splitting portion. The splitting portion may be coupled to the stiffening portion along an end section of the splitting portion. Alternatively, the splitting portion may be coupled to the stiffening portion along at least one edge of the splitting portion, optionally along at least two edges of the splitting portion, further optionally along three edges of the splitting portion. Advantageously, by coupling the splitting portion to the stiffening portion along at least one edge of the splitting portion, the stiffness of the splitting portion may be improved. By coupling the splitting portion to the stiffening portion along three edges of the splitting portion, the stiffness of the splitting portion may be maximised.

[0111] Optionally, a stiffness of the flow separator is such that a maximum deflection 5 of the flow separator during deposition is less than 3 mm. Further optionally, 5 may be less than 70 pm. Advantageously, if 6 is less than 70 pm, more conformal deposits, i.e. deposits which conform well to the flow separator, may be created.

[0112] Optionally, the flow separator comprises a plurality of securing portions for securing, optionally for clamping or fastening, the flow separator. Advantageously, by providing dedicated securing portions, the flow separator may be securable, independently of at least any edge of the substrate, without adversely affecting the flow splitting properties of the flow separator.

[0113] Further optionally, the flow separator comprises three securing portions, optionally wherein the plurality of securing portions are arranged about different edges of the flow separator.

[0114] In examples in which the flow separator comprises the stiffening portion, the securing portions may be arranged on the stiffening portion. Advantageously, by providing the securing portions on the stiffening portion, any adverse effect of securing (e.g. fastening or clamping) on the flow splitting properties of the flow separator may be prevented.

[0115] In examples in which the flow separator comprises the stiffening portion, the stiffening portion may be a supporting step coupled to one side of the splitting portion. The inventors have found that coupling such a supporting step to the splitting portion increases a stiffness of the flow separator. Indeed, by coupling, in particular brazing, a supporting step to an averted side of the flow separator, the supporting step may also serve as a shield of the substrate to prevent deposits building up on the averted side of the flow separator.

[0116] A height of the flow separator supporting step, that is a distance from the top of the step to the top of the flow separator, may be about 0 mm to about 25 mm, optionally about 10 mm to about 25 mm. A width of the flow separator supporting step may be about 0 mm to about 20 mm, optionally about 5 mm to about 20 mm.

[0117] In some embodiments, a height h of the flow separator may be up to about 40 mm. For example, the height h of the flow separator may be about 10 mm to about 40 mm, optionally about 16 mm to about 26 mm, in particular about 19 mm.

[0118] A thickness t of the flow separator may be about 0.1 mm to about 12 mm, optionally 0.4 mm to about 5 mm, further optionally 0.41 mm, or about 0.7 mm. It is noted that where the flow separator comprise a splitting portion and a stiffening portion, the flow separator thickness relates to a thickness of the splitting portion.

[0119] The flow separator, in particular a, or the, splitting portion of the flow separator, may be a flat sheet, in particular a flat stainless steel sheet.

[0120] A deposition side surface of the flow separator to which the deposited structure is configured to conform may have a surface roughness of less than 10 pm, optionally less than 5 pm, further optionally less than 1 pm. Advantageously, the deposition side surface having a surface roughness of 1 pm may result in the deposit having a low surface roughness, avoiding any need for surface finishing of the deposited structure.

[0121] A surface of the deposited structure which conforms to the, deposition-side, surface of the flow separator, may have a surface roughness Ra of less than 5 pm. Advantageously, such a surface roughness Ra is comparable to milled components, eliminating the need for postdeposition finishing.

[0122] The flow separator may comprise, or be made from, a material which is harder than the powder material and sufficiently strong to withstand the heat and / or pressure of the flow of gas and powder (stream of material) without deforming (substantially).

[0123] In some embodiments, the flow separator may comprise, or be made of: titanium, stainless steel, or a ceramic, such as fused quartz.

[0124] In one example, the flow separator may be made of stainless steel 316L. In another example, the flow separator may be made of a material having a similar or greater hardness and Young’s modulus than 316L.

[0125] Additionally or alternatively, the flow separator may comprise at least one strengthening means. The at least one strengthening means may comprise at least one of: a reinforcing element, such as at least one supporting rib; a curvature; and a variable thickness. Providing a strengthening means may allow the flow separator to be made of a wider variety of materials, to have a lower thickness, and / or to have a greater height.

[0126] Optionally, the flow separator may be secured to the deposition nozzle. Advantageously, securing the flow separator to the deposition nozzle may allow a relative alignment of the flow separator and the deposition nozzle to be more easily controlled, and to be retained. Closely controlling the relative alignment of the flow separator and the deposition nozzle may facilitate consistent deposition results.

[0127] The flow separator may comprise a pattern for patterning the deposited flow of material. In particular, the pattern may be provided on the surface of the flow separator to which the deposited structure is configured to conform, with a pattern. The pattern may be a regular, or repeating pattern, or it may be a unregular pattern.

[0128] Optionally, the apparatus may be configured so that the flow separator is angleable, or angled, relative to the substrate relative to being perpendicular to the substrate by a separator-substrate angle (p. Optionally, (p is about 5° toward a, or the, deposition zone, to about 20° away from a, or the, deposition zone. Further optionally, (p is about 5° to about 15° away from a, or the, deposition zone. Yet further optionally, (p is about 10° away from a, or the, deposition zone. Advantageously, angling the flow separator, in particular angling the flow separator away from a deposition zone, may allow for improved deposition efficiency.

[0129] Optionally, the apparatus may be configured so that the deposition nozzle is angleable, or angled, relative to being perpendicular to the substrate by a nozzle-substrate angle p. Optionally, is about 2° toward a, or the, deposition zone, to about 15° away from a, or the, deposition zone; further optionally p is about 2° to about 10° away from a, or the, deposition zone; yet further optionally p is about 5° away from a, or the, deposition zone.

[0130] The apparatus may be configured so that the deposition nozzle and the flow separator are arrangeable at a relative angle RA to one another. Optionally, the relative angle RA between the deposition nozzle and the flow separator may be about 0.01 ° to about 22°, or about 0.1° to about 20°, or about 0.5° to about 15°, or about 1 ° to about 10°, or about 2° to about 5°. As will be apparent to those skilled in the art, RA is dependent on (p and p.

[0131] If RA is less than 0°, the flow separator will cast a shadow over the deposition zone, physically blocking particles from reaching the deposition zone. The inventors have found that this may be the case even if the deposition nozzle is fractionally offset, toward the deposition zone (RX < 0mm), causing trench formation. Optionally, the apparatus may be configured so that the flow separator may be movable, relative to the substrate and the deposition nozzle, by: translating the flow separator in a x-y plane, the x-y plane being defined by the substrate; translating the flow separator in a z direction, the z direction being normal to a, or the, x-y plane defined by the substrate; rotation about a z direction, the z direction being normal to a, or the, x-y plane defined by the substrate; rotation about a first direction defined by a, or the, x-y plane being defined by the substrate; and rotation about a second direction defined by the x-y plane, perpendicular to the first direction.

[0132] The apparatus may comprise a linear actuator for each translatory degree of freedom, and the apparatus may comprise a rotary actuator for each rotary degree of freedom, in which the flow separator is movable.

[0133] The apparatus may be configured so that the flow separator has up to six degrees of freedom. For ease of reference, rotation about the z direction may be referred to as “yaw”, rotation about a first direction (x direction) defined by the x-y plane may be referred to as “pitch”, and rotation about a second direction (y direction) may be referred to as “roll”.

[0134] (p may be defined as the angle of the flow separator relative to the z direction. Similarly, may be defined as the angle of the deposition nozzle relative to the z direction.

[0135] The flow separator may be arranged, or arrangable, relative to the deposition nozzle so that a nozzle standoff distance d is about 0 mm to about 50 mm, optionally 40 mm. The nozzle standoff distance is defined as a distance between a top face of the flow separator and an outlet of the nozzle.

[0136] The apparatus may comprise at least one linear or rotary actuator for moving the nozzle to perform various passes. The at least one linear or rotary actuator may be configured to move the nozzle centreline along the flow separator. The at least one linear or rotary actuator may be configured to move the nozzle centreline away from the flow separator, move the nozzle centreline along the flow separator in an opposite direction, and move the nozzle centreline towards the flow separator.

[0137] According to a third aspect of the disclosure there is provided a thermal spray deposition method for additive manufacturing. The method according to the third aspect of the disclosure comprises the steps of: arranging a deposition nozzle for depositing a material onto a substrate; arranging a flow separator, relative to the substrate and the deposition nozzle, so that the flow separator is positioned to split a flow of material emanating from the deposition nozzle, and to allow the material deposited on the substrate to form a structure conforming to a surface of the flow separator, wherein arranging the flow separator relative to the substrate comprises angling the flow separator relative to being perpendicular to the substrate by a separator-substrate angle cp; and spraying a flow of material through the deposition nozzle to deposit the material on the substrate to form a structure conforming to the surface of the flow separator.

[0138] Optionally, (p is about 5° toward a, or the, deposition zone, to about 20° away from a, or the, deposition zone, optionally wherein (p is about 5° to about 15° away from a, or the, deposition zone, optionally wherein (p is about 10° away from a, or the, deposition zone.

[0139] Further features of the method according to the third aspect of the present disclosure may be as set out above with reference to the method according to the first aspect of the present disclosure.

[0140] According to a fourth aspect of the disclosure there is provided a thermal spray deposition method for additive manufacturing. The method according to the fourth aspect of the disclosure comprises the steps of: arranging a deposition nozzle for depositing a material onto a substrate; arranging a flow separator, relative to the substrate and the deposition nozzle, so that the flow separator is positioned to split a flow of material emanating from the deposition nozzle, and to allow the material deposited on the substrate to form a structure conforming to a surface of the flow separator, wherein arranging the deposition nozzle and arranging the flow separator comprises arranging the deposition nozzle and the flow separator so that a centreline of the deposition nozzle is offset from a deposition-side distal corner of the flow separator, in a direction of a deposition zone, by about 0.1 PD to about 10 PD, wherein PD is a particle diameter of particles in the flow of material; and spraying a flow of material through the deposition nozzle to deposit the material on the substrate to form a structure conforming to the surface of the flow separator. Optionally, the centreline of the deposition nozzle is offset by about 0.5 PD to about 5 PD, or by about 1 PD to about 2 PD

[0141] Further features of the method according to the fourth aspect of the present disclosure may be as set out above with reference to the method according to the first aspect of the present disclosure.

[0142] Features described above in relation to any one aspect of the disclosure are equally applicable, mutatis mutandis, to every other aspect of the disclosure.

[0143] According to a fifth aspect of the present disclosure, there is provided a three-dimensional component manufactured according to the method of the first, third or fourth aspect, or a three- dimensional component manufactured using the apparatus of the second aspect.

[0144] Where reference is made herein to an “averted” side of the flow separator and a deposition side of the flow separator, or relative terms such as “bottom”, “top”, “lower”, “upper”, “distal”, “proximal” have been used, such descriptors relate to the apparatus when positioned ready for use, or the method being realised.

[0145] Brief Description of the Drawings

[0146] The disclosure will now be described, by way of example only, by reference to the following figures, in which:

[0147] Figure 1a shows a schematic of a known cold spray deposition apparatus;

[0148] Figure 1b shows a schematic of a known supersonic laser deposition SLD apparatus;

[0149] Figure 2 shows a schematic of a thermal spray deposition TSD apparatus;

[0150] Figure 3 shows a schematic of a further thermal spray deposition TSD apparatus;

[0151] Figure 4a shows a schematic of a TSD apparatus according to the present disclosure;

[0152] Figure 4b shows a schematic of the TSD apparatus of Figure 4a in a different configuration;

[0153] Figure 4c shows a schematic top view of the TSD apparatus of Figure 4a / 4b in a specific configuration; Figure 5 shows a schematic of, and a schematic top view of, various parameters which may be adjusted in a TSD apparatus according to the present disclosure;

[0154] Figure 6a, 6b, and 6c show perspective views of example flow separators suitable for use in a TSD apparatus according to the present disclosure.

[0155] Figure 7a shows constructional drawings of the example flow separator of Figure 6a;

[0156] Figure 7b shows constructional drawings of an alternative example of a flow separator similar to the example flow separator of Figure 6a;

[0157] Figure 8 shows a table setting out examples of suitable parameter selections for obtaining high quality three-dimensional deposits using a method or an apparatus according to the disclosure, as well as a top view showing a path of the nozzle during deposition;

[0158] Figure 9 shows a perspective view of a deposited structure and a corresponding schematic cross-section, A) deposited without a flow separator and B) deposited with a flow separator;

[0159] Figure 10 shows examples of deposited structures, using a method or an apparatus according to the present disclosure, with a shallow trench (Section a) or no trench (Section P);

[0160] Figure 11 shows various copper and titanium flat wall structures deposited using a method or an apparatus according to the disclosure;

[0161] Figures 12a and 12b show perspective and side views, respectively, of a flanged titanium ring, and Figures 12c and 12d show schematics of an apparatus for manufacturing a flanged titanium ring;

[0162] Figure 13 shows a perspective view of a TSD apparatus in which a flow separator suspender is arranged to couple a brazed flow separator relative to the nozzle; and

[0163] Figure 14 shows a flow diagram of an example of a method according to the disclosure.

[0164] Specific Description

[0165] Figure 1a shows a schematic diagram of a known cold spray deposition apparatus 100. The cold spray deposition apparatus comprises a source 102 of compressed gas, in this case a set of nitrogen cylinders. The process gas is oxygen-free compressed nitrogen (99.998% purity), of which about 90% is provided through a 30-kW gas heater 108, with the remainder being mixed with precursor material (metal powder) particles from a powder feeder 104, entraining the metal powder particles in the gas along mixer line 106. Both the gas with entrained particles in mixer line 106 and heated gas from gas heater 108 are directed to a de Laval nozzle 110 arranged for depositing a flow of material onto a substrate 112 for coating the substrate 112.

[0166] Figure 1 b shows a schematic of a supersonic laser deposition SLD apparatus 113, in which a material is deposited to form a three-dimensional structure 114. The area (in the plane defined by the substrate 112, the “x-y” plane) covered by the deposit shown in Figure 1 B defines the nozzle footprint diameter NFD. The SLD apparatus 113 comprises a laser 116 and a pyrometer 118, and is configured to heat deposited material in the deposition zone to between about 30% and 80% of precursor particle melting point.

[0167] Figure 2 shows a schematic of a thermal spray deposition TSD apparatus 200. The TSD apparatus 200 comprises a de Laval nozzle 210, with a centreline C of the deposition nozzle 210 slightly offset toward a deposition side DS of a flow separator (FS) 202.

[0168] The flow separator 202 is a stiff, substantially flat stainless steel sheet. The flow separator 202 separates the deposition side DS from an averted side AS. The material builds up a three- dimensional structure 204 on the deposition side DS, the structure 204 conforming to the deposition side DS surface of the flow separator 202. The flow separator 202 is held between the substrate 112 and a supporting substrate 206.

[0169] Figure 3 shows a schematic of a thermal spray deposition TSD apparatus 300, in which a de Laval nozzle 310 is shown at three different nozzle-substrate angles p, with a corresponding centreline C and a flow of powder 314. In the left hand portion, is angled toward a deposition zone / deposition side, resulting in a possibly shaded portion 316 on an averted side of the flow separator 302. In the middle portion, p is 0°, with the centreline C and the (longitudinal axis of the) flow separator 302 coinciding. In the right hand portion, p is angled away from a deposition zone, resulting in a potentially shaded portion 318 on an deposition side of the flow separator 302.

[0170] Figure 4a shows a TSD apparatus 400 according to the present disclosure. It is substantially similar to the TSD apparatus shown in the middle portion of Figure 3, in that the nozzle 410 is arranged so that its centreline C coincides with the Z axis and the flow separator 402 extends along the Z axis. It is also similar to the TSD apparatus shown in Figure 2. However, the TSD apparatus 400 differs from these other TSD apparatuses in that the flow separator 402 is positionably-secured relative to the nozzle 410 and the substrate 112 independently of an edge of the substrate 112 - in the TSD apparatus 300 of Figure 3 and in the TSD apparatus 200 of Figure 2, the flow separator 302 is secured to an edge of the substrate 112, between the substrate 112 and a sacrificial substrate 206.

[0171] The flow separator 402 is positioned on top of the substrate 112, and is in contact with the substrate 112, so that there is no gap between the flow separator 402 and the substrate 112.

[0172] Figure 4b shows the TSD apparatus 400 in a different configuration, in which the nozzle 410 is angled relative to being perpendicular to the substrate 112 by a nozzle-substrate angle and in that the flow separator 402 is angled relative to being perpendicular to the substrate 112 by a flow separator-substrate angle cp. The relationship between these angles will be explored in more detail below. It is noted that this arrangement may improve efficiency of a cold spray deposition process, by increasing the proportion of powder particles in a flow of particles which are deposited in the deposition zone, relative to the arrangement shown, e.g., in Figure 4a.

[0173] Figure 4c shows a schematic top view of the TSD apparatus 400 of Figure 4a / 4b in a specific configuration. In this example, the flow separator 402 is angled relative to the Y axis by a separator-to-Y-axis angle i . If the nozzle 410 moves along nozzle path C” (that is, a centreline C of the nozzle 410 moves along nozzle path C”) which extends in the direction of the Y axis, a distance RX between a proximal end of the flow separator and a centreline of the deposition nozzle may vary.

[0174] Figure 5 shows a summary of the various parameters which may be adjusted to maximise efficiency, or to improve the three-dimensions structure being deposited, in the method according to the present disclosure. Most of these parameters have already been discussed above.

[0175] The parameters shown in the schematic of Figure 5 not yet discussed are h, t, 5, and d. h and t relate to the height (h) and thickness (t) of the flow separator. 5 relates to the maximum deflection of the flow separator during deposition, which is dependent on a stiffness of the flow separator. The stiffness of the flow separator is dependent on various parameters, including h, t, and the material of the flow separator. Finally, d relates to the distance between a distal end of the nozzle 410 and a proximal end of the flow separator 402, which may be referred to as a nozzle-to-separator distance.

[0176] Table 1 below summarises the parameters and sets out some ranges which have been found to result in suitable deposits. When RX = 0, a positive p means the nozzle is facing the flow separator, and a negative means the nozzle is facing away from the flow separator. When RX = 0, a positive cp means the flow separator leans over the averted side, and a negative cp means the flow separator leans over the deposition site. This is shown in Figure 5, where the arrows on p and cp show which way the positive angle is defined.

[0177] For RX, positive values relate to the nozzle centreline being offset away from a deposition zone, that is towards the averted side of the flow separator 402, and negative values relate to the nozzle centreline being offset towards the deposition zone, that is towards the deposition side of the flow separator 402.

[0178] Table 1 - Parameters

[0179] Parameter Description Range

[0180] <P (°) Angle between the FS and Z-axis

[0181] P C) Angle between the nozzle and the Z-axis -2 to 15

[0182] RX (mm) Distance between the top of the FS mid-plane a -3 to 6 centreline

[0183] RXF The ratio of RX to the nozzle footprint diameter -0.125 to 0.75 h (mm) FS height t (mm) FS thickness 0.4 to 5 d (mm) Distance between top face of FS and the nozzle’s outlet ip (°) Angle between the FS and the Y axis -90 to 90

[0184] 6 (mm) Deflection of the top edge of the FS from its original position during deposition

[0185] (p and p make up the relative angle RA between the deposition nozzle and the flow separator.

[0186] Figures 6a, 6b, and 6c show example flow separators 602a, 602b, and 602c suitable for use in the apparatus 400 according to the present disclosure. Each of the flow separators 602a, 602b, and 602c comprises a splitting portion 620a, 620b, 620c arranged for splitting the flow of material, and a stiffening portion 622a, 622b, 622c to which the splitting portion 620a, 620b, 620c.

[0187] In “custom geometry v3” flow separator 602a, the splitting portion 620a is provided in a recess in the stiffening portion 622a. Figure 6a shows the flow separator 602a from an averted side. In this flow separator 602a, stiffness of the flow separator 602a is increased relative to a flat plate between a substrate 112 and a sacrificial substrate 206 (as shown for flow separator 202 in Figure 2), by increasing the number of fixed edges. It was found that relative to a 25x60x0.5 mm flat plate flow separator fixed between two substrates at a bottom edge, maximum deflection during cold spray deposition was reduced by 39 %, from about 600 pm to about 365 pm. The flow separator 602a, as shown in Figure 7a, has a length of 140 mm, with the splitting portion 620a having a length of 60 mm and a height of 11 mm. The stiffening portion has a total height of 20 mm. In this example, the step height SH is 9 mm and the step width SW is 5 mm.

[0188] An alternative example of flow separator 602a’ has a length of 140 mm, with the splitting portion 620a having a length of 60 mm and a height of 16 mm, as shown in Figure 7b. The stiffening portion 622a has a total height of 25 mm, with the splitting portion 620a arranged in the middle, lengthwise, of the stiffening portion 622a. In this example, the step height SH is 16 mm and the step width SW is 6.5 mm.

[0189] It is noted that the flow separators 602a and 602a’ are shown in Figures 7a and 7b so that a distal end, that is an end of each respective flow separator 602a and 602a’ which in use is further from the deposition nozzle, and closer to (or in contact with) the substrate, is shown at the top, and a proximal end, that is an end of each respective flow separator 602a and 602a’ is shown at the bottom. In contrast, Figures 6a to 6c show the flow separators 602a, 602b, and 602c in the correct orientation for use.

[0190] In “brazed” flow separator 602b, the splitting portion 620b is secured on top of a stiffening rod 622b by brazing. Figure 6b shows the flow separator 602b from a deposition side. The splitting portion 620b extends only partially along a length of the stiffening rod 622b. The flow separator 602b has a length of 140 mm, with the flat sheet splitting portion 620b having a length of 60 mm and the stiffening portion 622b having a height of 8 mm. In the brazed flow separator 602b, the step height SH is about 1 mm and the step width SW is about 5 mm.

[0191] In “custom geometry v1” flow separator 602c, the splitting portion 620c is secured on top of the stiffening portion 622c, and extends along the entire length of the stiffening portion 622c. Figure 6c shows the flow separator 602c from an averted side. The flow separator 602c has a length of 140 mm, and may have a height of 20 mm, or of 25 mm.

[0192] Each of the flow separators 602a, 602b, and 602c comprises securing portions 624 (e.g. for clamping / fastening), allowing for the flow separator to be positionably-securable independently of a substrate.

[0193] In alternative examples, rather than using a flow separator such as 602a, 602b, and 602c, a flat sheet flow separator, i.e. a separator not having a stiffening portion, may be used. Such a flat sheet flow separator may have a thickness of about 0.5 mm to about 0.7 mm, a length of about 60 mm to about 105 mm, and a height of about 30 mm to about 55 mm. The flow separators are made of stainless steel 316L. A Young’s modulus of the material of the flow separators may be 90 GPA to 100 GPA. The deposition side surface of the separator, to which the structure being deposited conforms, has a surface roughness of less than 1 pm.

[0194] Further suitable process parameters for TSD apparatus 400, in particular a cold spray deposition apparatus, are set out below in Table 2.

[0195] Table 2

[0196] It is noted that a “powder gas mass flow rate”, i.e. an amount of powder introduced via the powder feeder 104 into the gas flow, should be such that when the flow carrying the gas / powder mixture is combined with the (heated) main gas flow, the heated main gas flow is not significantly cooled and the direction of the main gas flow is not affected significantly. The trade-off between efficiency and quality of deposit will depend on the desired result. A heated main gas flow may be considered to not be significantly cooled if its temperature, in Kelvin, is reduced by less than 20%, or less than 10%, or less than 5%, or less than 2%. In one suitable example, a powder carrier gas flow of 150 slpm is used, which is about 8% of the total gas flow through the nozzle. In this example, the powder mass flow rate is less than 5% of the gas mass flow rate.

[0197] Figure 8 shows a table setting out examples of suitable parameter selections for obtaining high quality three-dimensional deposits, i.e. deposits in which the surface of the deposited structure which conforms to the deposition-side surface of the flow separator has a surface roughness Ra less than 5 pm, and in which there is no, or only shallow, trench formation (as discussed below). Figure 8 also shows the path of the nozzle during deposition. If there is no step-over then the nozzle traverses only along the Y-axis, adjacent the flow separator.

[0198] For building three-dimensional structures, the aim of the method and apparatus according to the disclosure is to deposit flat walls conforming to the flow separator. Such deposits are characterised by having a vertical wall on the side facing the flow separator, rather than being symmetrical with a trapezoidal cross section (c.f. Figure 9, where A shows a symmetrical, rough deposit which results without a flow separator, and where B shows a deposit having a flat surface). It has been found that the flat surface is typically smoother, i.e. has a lower surface roughness Ra (less than 5 pm) than the surface of a cold spray deposit deposited without a flow separator, which typically has a Ra above 20 pm.

[0199] A trench is defined as a gap between the peak of the deposited structure and the flow separator FS. Its presence was found in some cases to reduce conformity of the deposited structure to the flow separator. The deposit between the trench and the flow separator may be referred to as a “sheet”, because it is typically a thin sheet-like deposit.

[0200] The inventors have found that a trench is a self-perpetuating feature, i.e. a trench forms on a first pass, and becomes increasingly greater with each pass. Setting parameters to avoid trench formation may lead to improved three dimensional structures, i.e. structures having improved conformity to the deposition side surface of the flow separator.

[0201] Examples of a deposit with a shallow trench and no trench are shown in Figure 10 as Section a and Section p, respectively. These deposits with shallow trench and no trench were both considered smooth, i.e. having a surface roughness Ra less than 5 pm.

[0202] Figure 11 shows various copper and titanium flat wall structures deposited using a method according to the disclosure. As is apparent from Figure 11 , because the flow separator was positionably-securable independently of the substrate, the three dimensional structures may be built up anywhere on the substrate. The top right hand portion of Figure 11 , marked 257.1 , shows a comparison between a deposit built up without a flow separator (bottom deposit) and a deposit built up to conform to a surface of a flow separator (top deposit).

[0203] Flow separators which are not a flat sheet, or do not at least have a flat sheet portion, may be used to achieve other three dimensional structures. For example, as shown in Figures 12a and 12b, a flanged titanium ring 1200 may be manufactured atop a circular substrate 1201, the flanged titanium ring comprising a ring portion 1202 and a flange 1204. A suitable set up for manufacturing such a flanged titanium ring 1200 is shown in Figures 12c and 12d, allowing for a two-step process, first forming a ring portion 1202 with the setup of Figure 12c and then depositing the flange 1204 with the setup of Figure 12d.

[0204] Figure 13 shows a TSD apparatus 1300 in which a flow separator suspender 1301 is arranged to couple the brazed flow separator 1310 relative to the nozzle 1302. In this way, in apparatus 1300, the flow separator 1310 is entirely uncoupled from the substrate 1312, i.e. the flow separator 1310 is positionably-securable independently of the substrate 1312.

[0205] In the example shown in Figure 13, the flow separator 1310 is arranged to be in contact with the substrate 1312, i.e. it is directly on top of the substrate 1312 to ensure the flow separator 1310 is sufficiently stiff to produce suitable deposits. However, as noted above, in some examples, a flow separator may be arranged so that is not in contact with the substrate, i.e. it may be above the substrate, and separated from the substrate by a gap.

[0206] As shown in Figure 13, the apparatus 1300 permits movement of the x and y stage 1304, has a controller for providing z displacements 1303, a calibration ball 1308 for adjusting a height, as well as controllers 1306 for controlling RX and (p angle.

[0207] Figure 14 shows a flow diagram of a method 1400 according to the present disclosure. As shown in Figure 14, the method comprises arranging 1402 a deposition nozzle for depositing a material onto a substrate. The method further comprises arranging 1404 a flow separator, relative to the substrate and the deposition nozzle, so that the flow separator is positioned to split a flow of material emanating from the deposition nozzle, and to allow material deposited on the substrate to form a structure conforming to a surface of the flow separator, wherein the flow separator is positionably-securable independently of any edge of the substrate.

[0208] The method further comprises spraying 1406 a flow of material through the deposition nozzle to deposit the material on the substrate to form a structure conforming to the surface of the flow separator.

[0209] The flow separator may be positionably-securable independently of the substrate. Parameters and their impact on deposits

[0210] The inventors have found that when particles landed less than 50 pm from the flow separator, the deposits were consistently of a high quality. Whenever the orientation and position of the flow separator is such that a shadow is cast on the deposition site, particles landed much further from the flow separator, resulting in possible trench formation

[0211] High quality deposits are obtained when the concentration of particles increases up to the flow separator. An important parameter responsible for this is RX. It was found that the influence of RX was greater than the influence of the orientation (i.e. angle relative to the substrate) of the nozzle and the flow separator.

[0212] The inventors have found that it is possible to optimise RX and the orientation of the flow separator and the nozzle to avoid trench formation and achieve maximum efficiency.

[0213] • RX

[0214] If RX<0 mm, in other words if the nozzle is offset relative to the flow separator in a deposition side direction, trench formation was typically observed. This is because the nozzle centreline and thus, the peak of the deposited structure is separated from the flow separator.

[0215] If the nozzle is over to the other side of the flow separator, i.e. if it is offset in an averted side direction, then the theoretical peak of the deposited structure will be on the averted side of the flow separator. Instead, the deposit will be built against the flow separator, eliminating the trench.

[0216] On the other hand, it is apparent that the further the nozzle centreline is offset in an averted side direction, the smaller the proportion of the material which is deposited on the deposition site. Therefore, to reduce waste and maximise deposition rate, the nozzle centreline should be positioned substantially in line with the flow separator. The trade-off between trench formation and deposition rate must be considered, and will depend on desired results.

[0217] • Relative angle (RA)

[0218] The most significant parameter determining trench formation is the relative angle RA, which depends on and (p angles.

[0219] As already set out above, RA is the angle between the deposition nozzle and the flow separator. If RA is less than 0°, the flow separator is likely to cast a shadow over the deposition zone, physically blocking particles from reaching the deposition zone. The inventors have found that this may be the case even if the deposition nozzle is fractionally offset, toward the deposition zone (RX < 0mm), because of trench formation.

[0220] The inventors have found that if RA is greater than 15°, particles may be deposited onto the flow separator.

[0221] • Flow separator thickness (t)

[0222] Flow separator thickness was found to affect likelihood of trench formation - in particular, the inventors have found that a thicker flow separator made trench formation less likely.

[0223] Most importantly, thicker flow separators are typically stiffer, meaning that they deflect less, thus making trench formation less probable.

[0224] The inventors found that a flow separator thickness, or splitting portion thickness, of 0.7 mm produced trenchless deposits independently of other process parameters. However, more specific process parameters may be required to achieve trenchless deposits when the flow separator thickness is less than 0.5 mm.

[0225] Although trenchless deposits are also achievable with a flow separator having a thickness of 0.9 mm or more, some deposit build up on the top face of the flow separator may be observed which was not found to occur when the flow separator thickness was less than 0.9 mm. Thus, the deposition efficiency was found to be higher for flow separators having a thickness less than 0.9 mm than for those having a thickness greater than 0.9 mm. t of 0.7 mm may be considered a suitable thickness for balancing stiffness with deposition efficiency.

Claims

CLAIMS1. A thermal spray deposition method for additive manufacturing, the method comprising the steps of: arranging a deposition nozzle for depositing a material onto a substrate; arranging a flow separator, relative to the substrate and the deposition nozzle, so that the flow separator is positioned to split a flow of material emanating from the deposition nozzle, and to allow material deposited on the substrate to form a structure conforming to a surface of the flow separator, wherein the flow separator is positionably-securable independently of any edge of the substrate; and spraying a flow of material through the deposition nozzle to deposit the material on the substrate to form a structure conforming to the surface of the flow separator.

2. A thermal spray deposition method according to claim 1 , wherein the thermal spray deposition method is one of: a plasma spray deposition method; a high velocity oxygen fuel HVOF coating method; a detonation spraying method; and a cold spray deposition method, optionally a supersonic laser deposition method.

3. A method according to claim 1 or 2, wherein the flow separator is positionably- securable independently of the substrate.

4. A method according to claim 1 , 2, or 3, wherein arranging the deposition nozzle and arranging the flow separator comprises arranging the deposition nozzle and the flow separator so that a centreline of the deposition nozzle is offset from a deposition-sidedistal corner of the flow separator, in a direction of a deposition zone, by about 0.1 PD to about 10 PD, wherein PD is a mean particle diameter of particles in the flow of material, optionally the centreline of the deposition nozzle is offset by about 0.5 PD to about 5 PD, or by about 1 PD to about 2 PD.

5. A method according to any preceding claim, wherein arranging the flow separator, relative to the substrate and the deposition nozzle, comprises arranging the flow separator so that a proximal end of the flow separator and a centreline of the deposition nozzle are offset by a distance RX.

6. A method according to claim 5, wherein the flow separator is offset by a distance RX: toward a deposition zone, optionally wherein NFD is a nozzle footprint diameter of the deposition nozzle, and RX is about 0.001 NFD to about 0.125 NFD, further optionally RX is about 0.01 NFD to about 0.1 NFD; or away from the deposition zone, optionally wherein NFD is a nozzle footprint diameter of the deposition nozzle, and RX is about 0.001 NFD to about 0.75 NFD, further optionally RX is about 0.1 NFD to about 0.5 NFD.

7. A method according to any preceding claim, wherein the flow separator comprises a stiffening portion, and a splitting portion for splitting the flow of material, coupled to the stiffening portion.

8. A method according to any preceding claim, wherein arranging the flow separator comprises securing, optionally fastening or clamping, the flow separator, optionally wherein securing the flow separator comprises laterally securing and / or vertically securing the flow separator, further optionally wherein securing the flow separator comprises laterally securing and / or vertically securing the flow separator at a plurality of securing portions.

9. A method according to claim 8 when dependent on claim 7, wherein securing the flow separator comprises clamping or fastening the flow separator at a plurality of securing portions on the stiffening portion, optionally at three securing portions, and optionally wherein the plurality of securing portions are disposed about different edges of the flow separator.3310. A method according to claim 8 or 9, wherein securing the flow separator comprises securing the flow separator to the deposition nozzle.11 . A method according to any preceding claim, wherein a stiffness of the flow separator is such that a maximum deflection 5 of the flow separator during deposition is less than 3 mm, optionally less than 70 pm.

12. A method according to any preceding claim, wherein a height h of the flow separator is up to about 40 mm, optionally about 16 mm to about 26 mm, in particular about 19 mm, and / or a thickness t of the flow separator is about 0.4 mm to about 5 mm, preferably 0.7 mm.

13. A method according to any preceding claim, wherein arranging the flow separator relative to the substrate comprises angling the flow separator relative to being perpendicular to the substrate by a separator-substrate angle cp, optionally wherein (p is about 5° toward a, or the, deposition zone, to about 20° away from a, or the, deposition zone; optionally wherein (p is about 5° to about 15° away from a, or the, deposition zone; further optionally wherein (p is about 10° away from a, or the, deposition zone.

14. A method according to any preceding claim, wherein arranging the deposition nozzle comprises angling the deposition nozzle relative to being perpendicular to the substrate by a nozzle-substrate angle p, optionally wherein is about 2° toward a, or the, deposition zone, to about 15° away from a, or the, deposition zone; optionally wherein p is about 2° to about 10° away from a, or the, deposition zone; further optionally wherein p is about 5° away from a, or the, deposition zone.

15. A method according to any preceding claim, wherein the deposition nozzle and the flow separator are arranged at an angle relative to one another, optionally wherein a relative angle RA between the deposition nozzle and the flow separator is about 0.01 ° to about 22°, or about 0.1 ° to about 20°, or about 0.5° to about 15°, or about 1 ° to about 10°, or about 2° to about 5°.

16. A method according to any preceding claim, further comprising patterning the material deposited on the substrate.

17. A thermal spray deposition apparatus for additive manufacturing, the apparatus comprising:a deposition nozzle for depositing a material onto a substrate; and a flow separator positionably-securable independently of any edge of the substrate; optionally the flow separator being positionably-securable independently of the substrate; wherein the flow separator is arrangeable, relative to the substrate and the deposition nozzle, to split a flow of material emanating from the deposition nozzle, and to allow material deposited on the substrate to form a structure conforming to a surface of the flow separator.

18. A thermal spray deposition apparatus according to claim 17, wherein the thermal spray deposition apparatus is one of: a plasma spray deposition apparatus; a high velocity oxygen fuel HVOF coating apparatus; detonation spraying apparatus; and a cold spray deposition apparatus, optionally a cold spray deposition apparatus further comprising a laser.

19. An apparatus according to claim 17 or 18, wherein the apparatus is configurable so that a centreline of the deposition nozzle is offset from a deposition-side distal corner of the flow separator, in a direction of a deposition zone, by about 0.1 PD to about 10 PD, wherein PD is a mean particle diameter of particles in the flow of material, optionally so that the centreline of the deposition nozzle is offset by about 0.5 PD to about 5 PD, or by about 1 PD to about 2 PD.

20. An apparatus according to claim 17, 18, or 19, wherein the apparatus is configurable so that a proximal end of the flow separator and a centreline of the deposition nozzle are offset by a distance RX, optionally wherein NFD is a nozzle footprint diameter of the deposition nozzle and the apparatus is configurable so that the centreline of the deposition nozzle is offset by RX:toward a deposition zone, and optionally RX is about 0.125 NFD to about 0.001 NFD, further optionally RX is about 0.1 NFD to about -0.01 NFD; or away from the deposition zone, and optionally RX is about 0.001 NFD to about 0.75 NFD, further optionally RX is about 0.1 NFD to about 0.5 NFD.21 . An apparatus according to any of claims 17 to 20, wherein the flow separator comprises a stiffening portion, and a splitting portion coupled to the stiffening portion.

22. An apparatus according to claim 21 , wherein the splitting portion is coupled to the stiffening portion along an end section of the splitting portion, or wherein the splitting potion is coupled to the stiffening portion along at least one edge of the splitting portion, optionally along at least two edges of the splitting portion, further optionally along three edges of the splitting portion.

23. An apparatus according to any of claims 17 to 22, wherein the flow separator comprises a plurality of securing portions for securing, optionally for clamping or fastening, the flow separator, optionally the flow separator comprises three securing portions, optionally wherein the plurality of securing portions are arranged about different edges of the flow separator, and when dependent on claim 21 or 22, wherein the securing portions are arranged on the stiffening portion.

24. An apparatus according to any of claims 17 to 22, wherein the flow separator is secured to the deposition nozzle.

25. An apparatus according to any of claims 17 to 24, wherein the flow separator comprises a pattern for patterning the deposited flow of material.

26. A thermal spray deposition method for additive manufacturing, the method comprising the steps of: arranging a deposition nozzle for depositing a material onto a substrate; arranging a flow separator, relative to the substrate and the deposition nozzle, so that the flow separator is positioned to split a flow of material emanating from the deposition nozzle, and to allow the material deposited on the substrate to form a structure conforming to a surface of the flow separator, wherein arranging the flow separator relative to the substrate comprises angling the flow separator relative to being perpendicular to36the substrate by a separator-substrate angle <p, optionally wherein (p is about 5° toward a, or the, deposition zone, to about 20° away from a, or the, deposition zone, optionally wherein (p is about 5° to about 15° away from a, or the, deposition zone, optionally wherein (p is about 10° away from a, or the, deposition zone; and spraying a flow of material through the deposition nozzle to deposit the material on the substrate to form a structure conforming to the surface of the flow separator.

27. A thermal spray deposition method for additive manufacturing, the method comprising the steps of: arranging a deposition nozzle for depositing a material onto a substrate; arranging a flow separator, relative to the substrate and the deposition nozzle, so that the flow separator is positioned to split a flow of material emanating from the deposition nozzle, and to allow the material deposited on the substrate to form a structure conforming to a surface of the flow separator, wherein arranging the deposition nozzle and arranging the flow separator comprises arranging the deposition nozzle and the flow separator so that a centreline of the deposition nozzle is offset from a deposition-side distal corner of the flow separator, in a direction of a deposition zone, by about 0.1 PD to about 10 PD, wherein PD is a mean particle diameter of particles in the flow of material, optionally the centreline of the deposition nozzle is offset by about 0.5 PD to about 5 PD, or by about 1 PD to about 2 PD; and spraying a flow of material through the deposition nozzle to deposit the material on the substrate to form a structure conforming to the surface of the flow separator.37

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