CA2215940C - Laser sintering apparatus for producing coatings and dense metal parts - Google Patents
Laser sintering apparatus for producing coatings and dense metal parts Download PDFInfo
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- CA2215940C CA2215940C CA002215940A CA2215940A CA2215940C CA 2215940 C CA2215940 C CA 2215940C CA 002215940 A CA002215940 A CA 002215940A CA 2215940 A CA2215940 A CA 2215940A CA 2215940 C CA2215940 C CA 2215940C
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- Laser Beam Processing (AREA)
- Powder Metallurgy (AREA)
Abstract
A laser sintering apparatus and method for producing dense three dimensional parts and a surface coating are disclosed. The disclosed apparatus comprises means for delivering a stream of material to an area on a surface to be built up, one or more lasers positioned with their axis at an acute angle to the normal to the surface impinging the area of deposited material and causing the material to adhere to the surface, and means for relative movement between the surface and both the delivering means and the lasers. In the one laser embodiment of the invention the axis of the delivering means is at an acute angle to the normal to the surface. Where a plurality of lasers is used, the delivering means is substantially normal to the surface. An even coating of material is thereby formed on the surface in all directions of movement. Dense shapes comprised of layers of coatings of material may thereby be built up. The material may be a metal in powder or thin wire form.
Description
LASER SINTERING APPARATUS FOR
PRODUCING COATINGS AND DENSE METAL PARTS
Field of the Invention The present invention relates to an apparatus for building dense metal (and alloy) parts and surface coating by material addition rather than machining (material removal), more particularly an arrangement for the delivery of metallic powder or wire to a melt pool created by laser beams.
Background of the Invention Laser cladding is a well known surface modification technique and is used to create a more wear and/or corrosion resistant surface on metallic components.
The clad material is either pre-placed on the surface or supplied in the form of powder during the process. The powder-feed cladding technique is more versatile and is commonly used.
A typical laser cladding set-up is shown in Figure 1. The powder is fed through a nozzle and the laser beam melts the powder along with the substrate. The sample is traversed in one direction to obtain a single pass. For wider area coverage overlapping passes are used, usually maintaining the same traversing direction. The amount of overlap per pass, laser power, powder feed rate, powder feed angle, traversing speed etc. are optimized to obtain the desired clad thickness and surface finish. It is well known that the thickness of the clad is dependant on the traversing direction. Different heights are obtained when the traversing direction is changed with respect to the laser beam and powder feed nozzle.
Hitherto the laser beam incident angle has always been maintained to be perpendicular to the surface in laser cladding for optimum energy absorption.
PRODUCING COATINGS AND DENSE METAL PARTS
Field of the Invention The present invention relates to an apparatus for building dense metal (and alloy) parts and surface coating by material addition rather than machining (material removal), more particularly an arrangement for the delivery of metallic powder or wire to a melt pool created by laser beams.
Background of the Invention Laser cladding is a well known surface modification technique and is used to create a more wear and/or corrosion resistant surface on metallic components.
The clad material is either pre-placed on the surface or supplied in the form of powder during the process. The powder-feed cladding technique is more versatile and is commonly used.
A typical laser cladding set-up is shown in Figure 1. The powder is fed through a nozzle and the laser beam melts the powder along with the substrate. The sample is traversed in one direction to obtain a single pass. For wider area coverage overlapping passes are used, usually maintaining the same traversing direction. The amount of overlap per pass, laser power, powder feed rate, powder feed angle, traversing speed etc. are optimized to obtain the desired clad thickness and surface finish. It is well known that the thickness of the clad is dependant on the traversing direction. Different heights are obtained when the traversing direction is changed with respect to the laser beam and powder feed nozzle.
Hitherto the laser beam incident angle has always been maintained to be perpendicular to the surface in laser cladding for optimum energy absorption.
2 "Rapid Prototyping" is a related technique; most of these techniques are based on layered manufacturing where a part is built as a series of horizontal layers, each one being formed individually and bonded to the preceding layer. The various processes differ in the way each layer is formed and the raw materials used but the underlying methodology is essentially the same in each case.
Stereolithography (SLA) and Selected Laser Sintering (SLS) are the two most common rapid prototyping processes. In both cases, a three dimensional CAD
model of a part is generated and sliced into horizontal layers. The sliced files are used for tool path generation to make a solid part layer by layer. The thickness of each slice is controlled and is determined by the degree of accuracy required and the capability of the system, viz-a-viz the maximum thickness that can be cured or sintered by the specific process.
The SLA process uses a photosensitive resin, which is cured layer by layer using an ultraviolet laser resulting in a cured resin part. In the SLS process a carbon dioxide laser of appropriate power is used to scan across the surface of a bed of a powdered thermoplastic material, sintering the powder into the shape of the required cross-section. A major limitation of the SLS process is its inflexibility in the selection of the composition of the metals or alloys that can be used. Further, the metal powders have to be specially coated with thermoplastic material.
In order to produce dense three dimensional metal/alloy parts, Los Alamos National Laboratory in the U.S. developed a process called "Directed Light Fabrication"
of complex metal parts (1994 ICALEO conference). In this process a coaxial powder delivery nozzle is used and a normal laser incident angle is maintained in this process.
The focused laser beam enters a chamber along the "z" (vertical) axis in the nozzle that
Stereolithography (SLA) and Selected Laser Sintering (SLS) are the two most common rapid prototyping processes. In both cases, a three dimensional CAD
model of a part is generated and sliced into horizontal layers. The sliced files are used for tool path generation to make a solid part layer by layer. The thickness of each slice is controlled and is determined by the degree of accuracy required and the capability of the system, viz-a-viz the maximum thickness that can be cured or sintered by the specific process.
The SLA process uses a photosensitive resin, which is cured layer by layer using an ultraviolet laser resulting in a cured resin part. In the SLS process a carbon dioxide laser of appropriate power is used to scan across the surface of a bed of a powdered thermoplastic material, sintering the powder into the shape of the required cross-section. A major limitation of the SLS process is its inflexibility in the selection of the composition of the metals or alloys that can be used. Further, the metal powders have to be specially coated with thermoplastic material.
In order to produce dense three dimensional metal/alloy parts, Los Alamos National Laboratory in the U.S. developed a process called "Directed Light Fabrication"
of complex metal parts (1994 ICALEO conference). In this process a coaxial powder delivery nozzle is used and a normal laser incident angle is maintained in this process.
The focused laser beam enters a chamber along the "z" (vertical) axis in the nozzle that
3 also delivers metal powder to the focal zone. The deposition is done on a base metal plate, which is removed after the part is built. The powders used for part build-up are 316 stainless steel, pure tungsten, nickel aluminide and molybdenum disilicide.
In a paper presented at a "Rapid Prototyping and Manufacturing "96"
conference (SME, Michigan, April 23-25, 1996) Dave Keicher of Sandia National Laboratories dealt with "Laser Engineered Net Shaping (LENS'''n') for Additive Component Processing" . This process used a Nd: YAG laser and a specialized coaxial powder delivery nozzle and powder feeder. It was concluded that with an off-axis (side) powder delivery system there is a strong directional dependence on the deposition geometry and accordingly a coaxial powder feed nozzle was used instead in the process permitting cladding independent of weld direction.
A rapid prototyping technique similar to the laser cladding process illustrated in Figure 1 has also been used by Prof. W. Steen (1994 ICALEO conference paper). A
machining pass is added after each build-up pass, and a high power carbon dioxide laser ( > 2 kw) is used. Extensive work was done to develop optics for the beam delivery system and to incorporate it on an automatic tool changing system. The process requires that after each laser build-up pass, the metal layer is machined back to required dimensions, thus showing the lack of control on the laser build-up. It was also demonstrated that the change in cladding direction has a significant influence on the shape and quality of the build-up. Good quality clad with a regular shaped bead formed parallel to the flow direction but as the angle to the flow direction increased the quality deteriorated until clad perpendicular to the flow was of poor quality.
Machining removes
In a paper presented at a "Rapid Prototyping and Manufacturing "96"
conference (SME, Michigan, April 23-25, 1996) Dave Keicher of Sandia National Laboratories dealt with "Laser Engineered Net Shaping (LENS'''n') for Additive Component Processing" . This process used a Nd: YAG laser and a specialized coaxial powder delivery nozzle and powder feeder. It was concluded that with an off-axis (side) powder delivery system there is a strong directional dependence on the deposition geometry and accordingly a coaxial powder feed nozzle was used instead in the process permitting cladding independent of weld direction.
A rapid prototyping technique similar to the laser cladding process illustrated in Figure 1 has also been used by Prof. W. Steen (1994 ICALEO conference paper). A
machining pass is added after each build-up pass, and a high power carbon dioxide laser ( > 2 kw) is used. Extensive work was done to develop optics for the beam delivery system and to incorporate it on an automatic tool changing system. The process requires that after each laser build-up pass, the metal layer is machined back to required dimensions, thus showing the lack of control on the laser build-up. It was also demonstrated that the change in cladding direction has a significant influence on the shape and quality of the build-up. Good quality clad with a regular shaped bead formed parallel to the flow direction but as the angle to the flow direction increased the quality deteriorated until clad perpendicular to the flow was of poor quality.
Machining removes
4 the imperfections in shape and size of each built-up layer arising from the change in the clad direction.
U.S. Patent No. 5,038,014 issued August 18, 1991 to Pratt et al. teaches the use of a powder feed at an angle to the article surface in the range between 3 S
°- 60 ° in conjunction S with a laser beam impacting normally on the surface. Pratt et al.
contemplate that the manufactured article has a surface roughness requiring machining at the conclusion of the process (see col. 4, line 28, col. 6, line 43 and col. 7, line 4). This surface roughness is a feature of side nozzle powder delivery when used with a single laser beam impacting normally on the surface.
As such the configuration according to Pratt et al. builds unevenly in various directions in the xy-plane, the additional required step of machining after each deposition pass makes the process cumbersome and expensive. Complex parts, having narrow channels, or overhangs etc. will be very difficult to make. Depending on the geometry of the part, expensive lathe or milling machining is required with tool changing capabilities. Incorporation 1 S of laser, especially carbon dioxide laser, requires the addition of complex optics to the system.
The diameter of the machining tool further limits the process when sharp corners or close multiple thin walls are required to be built. Further, as the control on the build-up process is rather poor, most of the material is removed to maintain the geometry. This creates unnecessary waste of expensive material.
It is evident from the above that for building up metal parts using a carbon dioxide or Nd:YAG laser and metallic powder, side delivery always has a directional dependence on the build-up, and is either abandoned in favour of coaxial powder delivery or machining is employed after every pass to maintain dimensions. The trend is to use a coaxial powder delivery to obtain equal layer build-up in all directions. In addition it is apparent that 4a the incident laser beam is always normal to the surface of the base plate.
Several nozzle designs for coaxial powder feeding during laser cladding have been disclosed, for example: U.S. patent 4,724,299 (Hammeke, Feb. 9/88); U.S.
Patent
U.S. Patent No. 5,038,014 issued August 18, 1991 to Pratt et al. teaches the use of a powder feed at an angle to the article surface in the range between 3 S
°- 60 ° in conjunction S with a laser beam impacting normally on the surface. Pratt et al.
contemplate that the manufactured article has a surface roughness requiring machining at the conclusion of the process (see col. 4, line 28, col. 6, line 43 and col. 7, line 4). This surface roughness is a feature of side nozzle powder delivery when used with a single laser beam impacting normally on the surface.
As such the configuration according to Pratt et al. builds unevenly in various directions in the xy-plane, the additional required step of machining after each deposition pass makes the process cumbersome and expensive. Complex parts, having narrow channels, or overhangs etc. will be very difficult to make. Depending on the geometry of the part, expensive lathe or milling machining is required with tool changing capabilities. Incorporation 1 S of laser, especially carbon dioxide laser, requires the addition of complex optics to the system.
The diameter of the machining tool further limits the process when sharp corners or close multiple thin walls are required to be built. Further, as the control on the build-up process is rather poor, most of the material is removed to maintain the geometry. This creates unnecessary waste of expensive material.
It is evident from the above that for building up metal parts using a carbon dioxide or Nd:YAG laser and metallic powder, side delivery always has a directional dependence on the build-up, and is either abandoned in favour of coaxial powder delivery or machining is employed after every pass to maintain dimensions. The trend is to use a coaxial powder delivery to obtain equal layer build-up in all directions. In addition it is apparent that 4a the incident laser beam is always normal to the surface of the base plate.
Several nozzle designs for coaxial powder feeding during laser cladding have been disclosed, for example: U.S. patent 4,724,299 (Hammeke, Feb. 9/88); U.S.
Patent
5,418,350 (Freneaux, May 23/95); U.S. Patent 5,477,026 (Buongiorno, Dec.
19/95) and U.S.
Patent 5,111,021 (Jolys, May 5/92).
Off-axis lasers have only previously been used for drilling, cutting or welding.
No such orientations have been used for cladding or building up dense metal parts composed of layers of deposited material.
Summary of the Invention 5 As an alternative to coaxial powder feeding, and yet overcoming the above drawbacks of side nozzle powder delivery, in accordance with the present invention, an apparatus for depositing a layer of material on a surface comprising means for delivering at an acute angle to the normal to the surface a stream of material to an area on the surface (the "build-up area") and a laser positioned with its axis at an acute angle to the normal to the surface impinging the build-up area to cause the material to adhere to the surface and means for providing relative movement between the surface and both the delivering means and the laser. Normally the surface is moved while both the laser and delivery means remain stationary; a thin layer of fused material thereby forms on the surface in the direction of movement. The material may be metal in powder or thin wire form.
The directional dependence of the clad bead can also be avoided, in accordance with the present invention, if a plurality of lasers positioned with their axis at an acute angle to the normal to the surface impinge on the area containing the material.
A stream of material is delivered to this area at an angle substantially normal to the surface. Means provide for relative movement between the surface and both the delivering means and the lasers. An equal build-up of material is thereby obtained in all transversing directions without the use of a coaxial powder nozzle.
19/95) and U.S.
Patent 5,111,021 (Jolys, May 5/92).
Off-axis lasers have only previously been used for drilling, cutting or welding.
No such orientations have been used for cladding or building up dense metal parts composed of layers of deposited material.
Summary of the Invention 5 As an alternative to coaxial powder feeding, and yet overcoming the above drawbacks of side nozzle powder delivery, in accordance with the present invention, an apparatus for depositing a layer of material on a surface comprising means for delivering at an acute angle to the normal to the surface a stream of material to an area on the surface (the "build-up area") and a laser positioned with its axis at an acute angle to the normal to the surface impinging the build-up area to cause the material to adhere to the surface and means for providing relative movement between the surface and both the delivering means and the laser. Normally the surface is moved while both the laser and delivery means remain stationary; a thin layer of fused material thereby forms on the surface in the direction of movement. The material may be metal in powder or thin wire form.
The directional dependence of the clad bead can also be avoided, in accordance with the present invention, if a plurality of lasers positioned with their axis at an acute angle to the normal to the surface impinge on the area containing the material.
A stream of material is delivered to this area at an angle substantially normal to the surface. Means provide for relative movement between the surface and both the delivering means and the lasers. An equal build-up of material is thereby obtained in all transversing directions without the use of a coaxial powder nozzle.
6 Multiple lasers allow for the flexibility of creating thicker walls by a single pass, because a bigger spot may be obtained by focusing the lasers. A certain power density level within this spot can be maintained by controlling the power of the individual laser beams. A further advantage of this multiple laser beam technique is pre-heating and post-heating of the build-up in a single pass. Pre- and post-heating becomes very important when hard materials which are sensitive to thermal shock or materials that undergo cooling rate dependant transformations are used for building up parts.
One beam can be focused ahead of the point of build-up for pre-heating, while another beam can be made incident at a spot behind the point of build-up for post-heating and controlling the cooling rate.
The invention includes a method of depositing a coating of a material on a surface comprising the steps of delivering a stream of material impacting an area on the surface, providing either the above multiple or single laser arrangement and moving the surface and stream/laser arrangement relative to one another whereby an even coating is formed, using overlapping passes.
The invention also includes the method of building up repeated layers of coatings. It is therefore possible to produce complex dense three dimensional shapes comprised of layers of deposited material with the disclosed method.
Description of the Drawings The invention will be better understood from the following description, which relates to preferred embodiments, given by way of non-limiting examples, and explained with reference to the accompanying schematic drawings, in which:
One beam can be focused ahead of the point of build-up for pre-heating, while another beam can be made incident at a spot behind the point of build-up for post-heating and controlling the cooling rate.
The invention includes a method of depositing a coating of a material on a surface comprising the steps of delivering a stream of material impacting an area on the surface, providing either the above multiple or single laser arrangement and moving the surface and stream/laser arrangement relative to one another whereby an even coating is formed, using overlapping passes.
The invention also includes the method of building up repeated layers of coatings. It is therefore possible to produce complex dense three dimensional shapes comprised of layers of deposited material with the disclosed method.
Description of the Drawings The invention will be better understood from the following description, which relates to preferred embodiments, given by way of non-limiting examples, and explained with reference to the accompanying schematic drawings, in which:
7 Figure 1 is a diagrammatic representation of a front view of a prior art apparatus for laser cladding.
Figures 2a, 2b and 2c are diagrammatic representations of a front, side and overhead view respectively of an apparatus for building up dense metal parts with four off-axis lasers according to the invention.
Figure 3 is a front view similar to Figure 2 of a similar apparatus but using one off-axis laser according to the invention.
Figure 4 is a diagrammatic representation of areas impinged by lasers for pre-and post- heating.
Figs. 5 to 10 are photographs of parts built up with the apparatus according to the invention.
Figs. 11 and 12 are photographs of the cross-section of a wall built up with the apparatus according to the invention.
Figure 13 is a photograph of a complicated shape built up with the apparatus according to the invention.
Detailed Description of the Invention According to the invention, the apparatus is essentially constituted by a head supporting one or more lasers which direct a laser beam with its axis at an acute angle to the normal to a surface to be built up, also supporting a nozzle for delivering to the surface at an acute angle to the normal to the surface (in the one laser version) or substantially along the normal to the surface (in the multiple laser version) a stream of material so as to permit uniform build-up of the material independent of direction. The g surface is provided with means for translational movement in its own plane.
The material of the subject invention includes a metallic powder or thin wire or a ceramic powder.
In conventional laser cladding with powder feed, shown in Figure 1 of the accompanying drawings, powder is fed through a side delivery tube (12) and a laser (13) melts the powder (11) along with the substrate (14) to form a clad layer (15).
The sample is traversed in one direction ( 16) and the laser incident angle ( 8 ~ ) is always normal to the substrate for optimum energy absorption.
According to a first embodiment of the invention, shown in Figures 2a, 2b and 2c of the accompanying drawings, the apparatus comprises the powder delivery tube (21) positioned with its axis substantially along the normal to the surface ( N ) depositing the material in powder form to an area containing the axis of the tube (22) on the surface (23); two, three, four or more lasers ( L ) positioned with their axes at acute angles ( 8x to the normal to the surface impinging the area containing the axis of the tube (22) and means providing for movement between the surface and both the powder delivery tube and the lasers, whereby the powdered material forms an even coating whichever transversing direction is used (arrows x and y). The laser producing the beam is preferably of the Nd:YAG type. A carbon dioxide laser or another laser without fiber optic beam delivery may also be used. Both the lasers and the powder delivery tube are connected by conduits to a source of shielding gas such as argon (not shown); this acts as a carrier for the powder and also helps in keeping the laser focusing optics clean. The powder delivery tube may be 4 to 5 ° off the vertical according to the invention.
The four laser version of Figure 2 uses lasers (L) arranged evenly around a central powder delivery tube (21) having a vertical axis (N). Each laser is inclined inwardly, at the same angle ( b ) to the vertical, towards the axis of the delivery tube so that the laser axis meet that of the delivery tube at or close to a common area (22) on the surface (23). The angle of inclination ( 8 ) is preferably between 5 °
and 45 ° . When viewed from overhead (Figure 2c) the lasers are equally spaced around the powder delivery tube (8 = 45°). All four lasers may be separate small lasers, or supplied from a single laser provided with a beam sputter which divides the beam into four beams which are then transmitted to the four lasers by optical fibers. The lasers when focused at a single spot create a melt pool on the area containing the axis of the delivery tube (22) into which the powdered metal is fed.
The supporting head is fixed against movement in the horizontal plane, but is computer-controlled to move vertically as layers of material are built up on the surface.
The head therefore provides a Z-axis component of movement, while the surface provides relative movement in the X-Y plane. The arrangement is such that any desired shape can be built up on the surface by suitable movements of the surface while the powder delivery tube moves along the Z-axis concurrently with the lasers and delivers powdered metal to an impinged area on the surface. The apparatus of Figure 2 thereby permits an even coating to be deposited whichever traversing direction is used.
In operation, the laser melts a thin surface layer of the base, or of the previously deposited metal, along with the powder being delivered through the tube, to create a layer or band of fused metal powder metallurgically bonded to the first layer of known height and width. The head then raises the laser and powder delivery tube by a predetermined amount, for example a few thousandths of an inch, and a further layer is formed on the first; this time the powder and a part of the previous layer are melted.
This continues until the desired height is achieved.
Control of the process may be achieved by a CAD (computer aided design) package. The CAD file, through the use of suitable software, is sliced into layers of 5 known thickness, this being controlled by the process parameters. The sliced layers are used to generate tool paths to control the movements of CNC controlled motion system.
The program not only determines the path of movement of the laser beam and delivery tube combination, but also determines the vertical movement of the head needed to produce layers which have a build-up height determined by the operating parameters.
10 Depending on the desired use of the person working the invention, the lasers may be positioned with their axis at different acute angles (8,, 82, etc.) to the normal to the surface. For example in Figure 4 where pre- and post-heating of the build-up is performed one or more lasers are focused ahead (43) of a build-up area (41) and one or more lasers are focused behind (44) the build-up area (41) as a coating (42) is deposited.
In a preferred embodiment the lasers are dependently oriented and may be focused ahead or behind the build-up area by changing the angle ( 8 ) between the axis of the laser and the normal to the surface. Alternatively the lasers may be independently moved in the xy-plane, changing their relative position so as to impinge on a point ahead (43) or behind (44) the build-up area (41). It is expected that one skilled in the art could so change the relative orientation of the lasers.
Figure 4 shows an enlarged overhead view where the powder or wire material and the laser meet the surface. A laser may pre-heat or post-heat the build-up area at a point (43) or (44) entirely outside the build-up area (41), shown in Figure 4a. The build-up area is accordingly impinged by a plurality of acute incident lasers (where normal material delivery is used) or by a single acute incident laser (where material is delivered at an acute incident angle).
There may also be overlap between the build-up area (41) and the points of pre-heating (43) or post-heating (44) as shown in Figure 4b, such that some of the energy from the pre- and/or post- heating lasers also melts the material in the build-up area.
Accordingly in this embodiment the material is delivered along the normal to the surface, energy from one laser directly impinges the build-up area (41) at an acute incident angle, and one or more lasers partially impinges the build-up area in advance (43) and/or behind (44) the build-up area at an acute incident angle. Of course a plurality of lasers could be used to directly or partially impinge the build-up area. A non-laser could also be used for pre- and post- heating i.e. induction heat.
In a preferred embodiment where a first and second laser is used for directly melting the powder in the build-up area and a third laser is focused ahead and a fourth laser is focused behind the build-up area, the 4 lasers are spaced evenly in the x-y plane, (i.e. 90° apart, where 8 = 45° in Figure 2c).
The lasers may be unequally spaced in the plane of the surface around the central powder delivery tube with their axis positioned at different angles (
Figures 2a, 2b and 2c are diagrammatic representations of a front, side and overhead view respectively of an apparatus for building up dense metal parts with four off-axis lasers according to the invention.
Figure 3 is a front view similar to Figure 2 of a similar apparatus but using one off-axis laser according to the invention.
Figure 4 is a diagrammatic representation of areas impinged by lasers for pre-and post- heating.
Figs. 5 to 10 are photographs of parts built up with the apparatus according to the invention.
Figs. 11 and 12 are photographs of the cross-section of a wall built up with the apparatus according to the invention.
Figure 13 is a photograph of a complicated shape built up with the apparatus according to the invention.
Detailed Description of the Invention According to the invention, the apparatus is essentially constituted by a head supporting one or more lasers which direct a laser beam with its axis at an acute angle to the normal to a surface to be built up, also supporting a nozzle for delivering to the surface at an acute angle to the normal to the surface (in the one laser version) or substantially along the normal to the surface (in the multiple laser version) a stream of material so as to permit uniform build-up of the material independent of direction. The g surface is provided with means for translational movement in its own plane.
The material of the subject invention includes a metallic powder or thin wire or a ceramic powder.
In conventional laser cladding with powder feed, shown in Figure 1 of the accompanying drawings, powder is fed through a side delivery tube (12) and a laser (13) melts the powder (11) along with the substrate (14) to form a clad layer (15).
The sample is traversed in one direction ( 16) and the laser incident angle ( 8 ~ ) is always normal to the substrate for optimum energy absorption.
According to a first embodiment of the invention, shown in Figures 2a, 2b and 2c of the accompanying drawings, the apparatus comprises the powder delivery tube (21) positioned with its axis substantially along the normal to the surface ( N ) depositing the material in powder form to an area containing the axis of the tube (22) on the surface (23); two, three, four or more lasers ( L ) positioned with their axes at acute angles ( 8x to the normal to the surface impinging the area containing the axis of the tube (22) and means providing for movement between the surface and both the powder delivery tube and the lasers, whereby the powdered material forms an even coating whichever transversing direction is used (arrows x and y). The laser producing the beam is preferably of the Nd:YAG type. A carbon dioxide laser or another laser without fiber optic beam delivery may also be used. Both the lasers and the powder delivery tube are connected by conduits to a source of shielding gas such as argon (not shown); this acts as a carrier for the powder and also helps in keeping the laser focusing optics clean. The powder delivery tube may be 4 to 5 ° off the vertical according to the invention.
The four laser version of Figure 2 uses lasers (L) arranged evenly around a central powder delivery tube (21) having a vertical axis (N). Each laser is inclined inwardly, at the same angle ( b ) to the vertical, towards the axis of the delivery tube so that the laser axis meet that of the delivery tube at or close to a common area (22) on the surface (23). The angle of inclination ( 8 ) is preferably between 5 °
and 45 ° . When viewed from overhead (Figure 2c) the lasers are equally spaced around the powder delivery tube (8 = 45°). All four lasers may be separate small lasers, or supplied from a single laser provided with a beam sputter which divides the beam into four beams which are then transmitted to the four lasers by optical fibers. The lasers when focused at a single spot create a melt pool on the area containing the axis of the delivery tube (22) into which the powdered metal is fed.
The supporting head is fixed against movement in the horizontal plane, but is computer-controlled to move vertically as layers of material are built up on the surface.
The head therefore provides a Z-axis component of movement, while the surface provides relative movement in the X-Y plane. The arrangement is such that any desired shape can be built up on the surface by suitable movements of the surface while the powder delivery tube moves along the Z-axis concurrently with the lasers and delivers powdered metal to an impinged area on the surface. The apparatus of Figure 2 thereby permits an even coating to be deposited whichever traversing direction is used.
In operation, the laser melts a thin surface layer of the base, or of the previously deposited metal, along with the powder being delivered through the tube, to create a layer or band of fused metal powder metallurgically bonded to the first layer of known height and width. The head then raises the laser and powder delivery tube by a predetermined amount, for example a few thousandths of an inch, and a further layer is formed on the first; this time the powder and a part of the previous layer are melted.
This continues until the desired height is achieved.
Control of the process may be achieved by a CAD (computer aided design) package. The CAD file, through the use of suitable software, is sliced into layers of 5 known thickness, this being controlled by the process parameters. The sliced layers are used to generate tool paths to control the movements of CNC controlled motion system.
The program not only determines the path of movement of the laser beam and delivery tube combination, but also determines the vertical movement of the head needed to produce layers which have a build-up height determined by the operating parameters.
10 Depending on the desired use of the person working the invention, the lasers may be positioned with their axis at different acute angles (8,, 82, etc.) to the normal to the surface. For example in Figure 4 where pre- and post-heating of the build-up is performed one or more lasers are focused ahead (43) of a build-up area (41) and one or more lasers are focused behind (44) the build-up area (41) as a coating (42) is deposited.
In a preferred embodiment the lasers are dependently oriented and may be focused ahead or behind the build-up area by changing the angle ( 8 ) between the axis of the laser and the normal to the surface. Alternatively the lasers may be independently moved in the xy-plane, changing their relative position so as to impinge on a point ahead (43) or behind (44) the build-up area (41). It is expected that one skilled in the art could so change the relative orientation of the lasers.
Figure 4 shows an enlarged overhead view where the powder or wire material and the laser meet the surface. A laser may pre-heat or post-heat the build-up area at a point (43) or (44) entirely outside the build-up area (41), shown in Figure 4a. The build-up area is accordingly impinged by a plurality of acute incident lasers (where normal material delivery is used) or by a single acute incident laser (where material is delivered at an acute incident angle).
There may also be overlap between the build-up area (41) and the points of pre-heating (43) or post-heating (44) as shown in Figure 4b, such that some of the energy from the pre- and/or post- heating lasers also melts the material in the build-up area.
Accordingly in this embodiment the material is delivered along the normal to the surface, energy from one laser directly impinges the build-up area (41) at an acute incident angle, and one or more lasers partially impinges the build-up area in advance (43) and/or behind (44) the build-up area at an acute incident angle. Of course a plurality of lasers could be used to directly or partially impinge the build-up area. A non-laser could also be used for pre- and post- heating i.e. induction heat.
In a preferred embodiment where a first and second laser is used for directly melting the powder in the build-up area and a third laser is focused ahead and a fourth laser is focused behind the build-up area, the 4 lasers are spaced evenly in the x-y plane, (i.e. 90° apart, where 8 = 45° in Figure 2c).
The lasers may be unequally spaced in the plane of the surface around the central powder delivery tube with their axis positioned at different angles (
8 in Figure 2c) depending on the shape of the part to be built up. For example, an oval shape would require unequally spaced lasers.
In addition to pre- and post- heating, the use of multiple lasers permits more material to be deposited in a single pass thereby forming a thicker coating. A
larger impinging area with a laser-controlled power density is another advantage.
According to a second embodiment, shown in Figure 3 of the accompanying drawings, the powder delivery tube (31) is positioned at a first acute angle ( a ) to the normal to the surface (33), and one laser ( L ) is positioned with its axis at a second acute angle ( (3 ) to the normal to the surface impinging the area containing the axis of the tube (32); and means provide movement of the surface (33) relative to both the laser (L) and tube (31). The powdered material thus adheres to the surface and forms an even coating irrespective of the traversing direction. This apparatus permits an even build-up of deposited material (34) whichever traversing direction is used. The angles of this single laser embodiment are more critical than the multiple laser arrangement of Figure 2.
Preferably the powder delivery tube, the normal to the surface and the laser axis are positioned in one plane (i.e. the powder delivery tube and laser are 180° apart when viewed from overhead). This arrangement provides the highest efficiency apparatus.
In a preferred embodiment, the first (a) and second (~3) acute angles are between 5 ° and 45 ° to the vertical. An optimum coating using the apparatus according to Figure 3 is obtained with a first angle (cx) of 18 ° and a second angle ((3) of 15 ° .
The invention also includes the method of building up repeated layers of metal powder according to either the single or multiple laser apparatus. With the invention it is therefore possible to provide an alternative to coaxial powder-feeding nozzles for three dimensional consolidation and surface treatment. One or more off-axis lasers impinge a surface at an acute angle to the normal to the surface, in particular an area of materials deposited in a delivery tube at an acute angle to the normal to the surface (in the single laser embodiment) or along the normal to the surface (in the multiple laser version).
Minti-directional movements with controlled build-up of material in each pass of the both the delivery tube and laser relative to the surface is thereby achieved.
In some cases the laser and delivery tube can be mounted on a robotic arm or other positioning device and moved to obtain additional degrees of freedom in making certain shapes. This apparatus also permits flexibility in the selection of the metal material and the surface material. The metal may be in powder or thin wire form. The base material need only provide support to the edges without undue flexing, so low cost plain carbon steel can be used instead of expensive conventional tool steel.
In one successful test of the embodiment of Figure 3, the following parameters were used:
Powder particle size: -53 to +22~cm;
Powder composition: typical stainless steel with approximately the following composition range (element, % ): C 0.024; Si 0.45; Mn 1.42; P 0.27; S 0.003;
Cr 16.4;
Ni 10.4; Mo 2.23.
Powder feed rate: from 4 to 12 gm per min;
Shielding gas: argon at 15 cfh;
Angle « of powder nozzle: 18.5 ° from vertical;
Angle (3 of laser beam: 15 ° from vertical;
Laser Nd:YAG; energy: 6 to 12 J/P, 60 to 120 watts average power, beam spot size 0.020 to 0.060 inch diameter;
Travel speed: 0.03 to 0.09 inches/sec;
Typical layer thickness of 0.0061 inches, with a wall width of 0.039 inches can be produced. The total height of the built up area is dependent on the number of layers.
A number of parts were produced using the single off-axis laser beam and off-axis powder delivery apparatus of Figure 3.
Example 1 A first acute angle ( a ) of 18 ° and a second acute angle ( /3 ) of 15 ° was used to produce sample shapes. In all cases, 304 stainless steel powder with a delivery rate of about 8 gm/minutes was used. The laser operating parameters used for these samples were: 10 J/p, 10 Hz and 10 ms. These parameters built about 0.006"/pass in all directions in the xy-plane with a wall thickness of about 0.040" .
All the shapes produced showed excellent consistency in the wall thickness, heights and the surface finish (Figures 4-9). The vertical angles are exactly 90°with very even surfaces. The square tube of Figure 4 has a 0.34" height; the round tube of Figure 5 is 1.2" in height and has a 0.5" diameter and the "D" shape in Figure 6 is also 1.2" in height. Complex angled walls can also be built with this process; the rectangular tube of Figure 7 has one wall at a 12 ° angle and is 1.1 " in height; Figure 8 shows a rectangular tube with one wall having a semi-circular feature, and a height of 1.2" and Figure 9 shows a rectangular tube with one wall having a semi-circular feature at a 6 ° angle and a height of 1.25". Another example of a complex shape is shown in Figure 13.
Example 2 In order to test the tensile strength of the consolidated parts, twenty five samples were prepared on a 0.125" thick stainless steel base. The dimensions of the consolidated flat samples were 6" by 0.5" and 0.040" thickness. After consolidation the base plate was machined off using a cut-off saw. The flat consolidated samples were then machined to obtain the tensile test specimens in accordance to ASTM
specification having a gage length of 2" . The width of the specimens was left in "as consolidated"
condition, 5 i.e. no machining or grinding was done on the flat sides.
The tensile test specimens were made by using a commercially available powder, with the following nominal composition: C - 0.024 % , Si - 0.45 % , Mn - 1.42 % , P - 0.027 % , S - 0.003 % , Cr - 16.4 % , Ni - 10.4 % and Mo - 2.23 % . This composition generally represents 316 type stainless steel.
10 The tensile test results are shown in Table 1. A total of 25 tests were performed; as six samples broke outside of the gage length, the results of only 19 samples are reported. The samples exhibited a mean 0.2% yield strength of 343.8 MPa which is higher than the published value of 205 MPa for wrought sheet material in annealed condition (ASM Metals Handbook Ninth Edition, 1979, p. 21).
15 The laser consolidated samples exhibited higher average ultimate tensile strength, 560.2 MPa compared to the published value of 515 MPa for annealed stainless steel. However, the average elongation shown by the consolidated samples (35 %) is slightly lower than the published value of 40 % . This may be attributed to the increase in the strength, but it is still high, indicating excellent ductility.
In Figure 10 the cross-section of the build-up wall is shown at a lower magnification (50x). The incremental height build-up by each pass is clearly evident.
There is no evidence of porosity of cracking in the build-up. The wall thickness is approximately 0.040" .
Figure 11 shows the cross-section of the consolidated wall at a higher magnification (1000x). The microstructure consists of about 2 micrometer diameter cells at the centre of the wall. The diameter of the cells is slightly larger near the edges of the wall (4 micrometers), indicating a slightly slower cooling rate near the edges. This cellular morphology is typical of a rapidly solidified microstructure and contributes to the high strength shown by the consolidated samples.
In addition to the specific advantages of the multiple laser arrangement of Figure 2 outlined above, the apparatus of the subject invention provides other advantages over conventional coaxial nozzles. The arrangements as shown in Figures 2 and 3 are simple in design, cost effective (no complex coaxial nozzle is necessary; the only requirement being to maintain the necessary orientation) and easy to maintain (unlike coaxial nozzles where clogging is a common problem).
Of course, the invention is not limited to the embodiments described and shown in the accompanying drawings. Modifications remain possible, particularly as to the construction of the various elements, or by substitution of various elements, or by substitution of technical equivalents, without thereby departing from the scope of protection of the invention.
Table 1 Samlrle0.2'%~ UltimateElongatio Numbe Yeild Tensile n (~/~) r Strength Strength (MFa) (MPa) 1 328.6 522.7 24.8 2 352.2 593.2 4G.7 3 348.3 58G.G 4G.3 4 336.4 502.8 19.4 5 344.7 545.2 24.7 G 330 5(2.2 21.3 7 352.6 602.7 59.3 8 340.7 533.3 24.5
In addition to pre- and post- heating, the use of multiple lasers permits more material to be deposited in a single pass thereby forming a thicker coating. A
larger impinging area with a laser-controlled power density is another advantage.
According to a second embodiment, shown in Figure 3 of the accompanying drawings, the powder delivery tube (31) is positioned at a first acute angle ( a ) to the normal to the surface (33), and one laser ( L ) is positioned with its axis at a second acute angle ( (3 ) to the normal to the surface impinging the area containing the axis of the tube (32); and means provide movement of the surface (33) relative to both the laser (L) and tube (31). The powdered material thus adheres to the surface and forms an even coating irrespective of the traversing direction. This apparatus permits an even build-up of deposited material (34) whichever traversing direction is used. The angles of this single laser embodiment are more critical than the multiple laser arrangement of Figure 2.
Preferably the powder delivery tube, the normal to the surface and the laser axis are positioned in one plane (i.e. the powder delivery tube and laser are 180° apart when viewed from overhead). This arrangement provides the highest efficiency apparatus.
In a preferred embodiment, the first (a) and second (~3) acute angles are between 5 ° and 45 ° to the vertical. An optimum coating using the apparatus according to Figure 3 is obtained with a first angle (cx) of 18 ° and a second angle ((3) of 15 ° .
The invention also includes the method of building up repeated layers of metal powder according to either the single or multiple laser apparatus. With the invention it is therefore possible to provide an alternative to coaxial powder-feeding nozzles for three dimensional consolidation and surface treatment. One or more off-axis lasers impinge a surface at an acute angle to the normal to the surface, in particular an area of materials deposited in a delivery tube at an acute angle to the normal to the surface (in the single laser embodiment) or along the normal to the surface (in the multiple laser version).
Minti-directional movements with controlled build-up of material in each pass of the both the delivery tube and laser relative to the surface is thereby achieved.
In some cases the laser and delivery tube can be mounted on a robotic arm or other positioning device and moved to obtain additional degrees of freedom in making certain shapes. This apparatus also permits flexibility in the selection of the metal material and the surface material. The metal may be in powder or thin wire form. The base material need only provide support to the edges without undue flexing, so low cost plain carbon steel can be used instead of expensive conventional tool steel.
In one successful test of the embodiment of Figure 3, the following parameters were used:
Powder particle size: -53 to +22~cm;
Powder composition: typical stainless steel with approximately the following composition range (element, % ): C 0.024; Si 0.45; Mn 1.42; P 0.27; S 0.003;
Cr 16.4;
Ni 10.4; Mo 2.23.
Powder feed rate: from 4 to 12 gm per min;
Shielding gas: argon at 15 cfh;
Angle « of powder nozzle: 18.5 ° from vertical;
Angle (3 of laser beam: 15 ° from vertical;
Laser Nd:YAG; energy: 6 to 12 J/P, 60 to 120 watts average power, beam spot size 0.020 to 0.060 inch diameter;
Travel speed: 0.03 to 0.09 inches/sec;
Typical layer thickness of 0.0061 inches, with a wall width of 0.039 inches can be produced. The total height of the built up area is dependent on the number of layers.
A number of parts were produced using the single off-axis laser beam and off-axis powder delivery apparatus of Figure 3.
Example 1 A first acute angle ( a ) of 18 ° and a second acute angle ( /3 ) of 15 ° was used to produce sample shapes. In all cases, 304 stainless steel powder with a delivery rate of about 8 gm/minutes was used. The laser operating parameters used for these samples were: 10 J/p, 10 Hz and 10 ms. These parameters built about 0.006"/pass in all directions in the xy-plane with a wall thickness of about 0.040" .
All the shapes produced showed excellent consistency in the wall thickness, heights and the surface finish (Figures 4-9). The vertical angles are exactly 90°with very even surfaces. The square tube of Figure 4 has a 0.34" height; the round tube of Figure 5 is 1.2" in height and has a 0.5" diameter and the "D" shape in Figure 6 is also 1.2" in height. Complex angled walls can also be built with this process; the rectangular tube of Figure 7 has one wall at a 12 ° angle and is 1.1 " in height; Figure 8 shows a rectangular tube with one wall having a semi-circular feature, and a height of 1.2" and Figure 9 shows a rectangular tube with one wall having a semi-circular feature at a 6 ° angle and a height of 1.25". Another example of a complex shape is shown in Figure 13.
Example 2 In order to test the tensile strength of the consolidated parts, twenty five samples were prepared on a 0.125" thick stainless steel base. The dimensions of the consolidated flat samples were 6" by 0.5" and 0.040" thickness. After consolidation the base plate was machined off using a cut-off saw. The flat consolidated samples were then machined to obtain the tensile test specimens in accordance to ASTM
specification having a gage length of 2" . The width of the specimens was left in "as consolidated"
condition, 5 i.e. no machining or grinding was done on the flat sides.
The tensile test specimens were made by using a commercially available powder, with the following nominal composition: C - 0.024 % , Si - 0.45 % , Mn - 1.42 % , P - 0.027 % , S - 0.003 % , Cr - 16.4 % , Ni - 10.4 % and Mo - 2.23 % . This composition generally represents 316 type stainless steel.
10 The tensile test results are shown in Table 1. A total of 25 tests were performed; as six samples broke outside of the gage length, the results of only 19 samples are reported. The samples exhibited a mean 0.2% yield strength of 343.8 MPa which is higher than the published value of 205 MPa for wrought sheet material in annealed condition (ASM Metals Handbook Ninth Edition, 1979, p. 21).
15 The laser consolidated samples exhibited higher average ultimate tensile strength, 560.2 MPa compared to the published value of 515 MPa for annealed stainless steel. However, the average elongation shown by the consolidated samples (35 %) is slightly lower than the published value of 40 % . This may be attributed to the increase in the strength, but it is still high, indicating excellent ductility.
In Figure 10 the cross-section of the build-up wall is shown at a lower magnification (50x). The incremental height build-up by each pass is clearly evident.
There is no evidence of porosity of cracking in the build-up. The wall thickness is approximately 0.040" .
Figure 11 shows the cross-section of the consolidated wall at a higher magnification (1000x). The microstructure consists of about 2 micrometer diameter cells at the centre of the wall. The diameter of the cells is slightly larger near the edges of the wall (4 micrometers), indicating a slightly slower cooling rate near the edges. This cellular morphology is typical of a rapidly solidified microstructure and contributes to the high strength shown by the consolidated samples.
In addition to the specific advantages of the multiple laser arrangement of Figure 2 outlined above, the apparatus of the subject invention provides other advantages over conventional coaxial nozzles. The arrangements as shown in Figures 2 and 3 are simple in design, cost effective (no complex coaxial nozzle is necessary; the only requirement being to maintain the necessary orientation) and easy to maintain (unlike coaxial nozzles where clogging is a common problem).
Of course, the invention is not limited to the embodiments described and shown in the accompanying drawings. Modifications remain possible, particularly as to the construction of the various elements, or by substitution of various elements, or by substitution of technical equivalents, without thereby departing from the scope of protection of the invention.
Table 1 Samlrle0.2'%~ UltimateElongatio Numbe Yeild Tensile n (~/~) r Strength Strength (MFa) (MPa) 1 328.6 522.7 24.8 2 352.2 593.2 4G.7 3 348.3 58G.G 4G.3 4 336.4 502.8 19.4 5 344.7 545.2 24.7 G 330 5(2.2 21.3 7 352.6 602.7 59.3 8 340.7 533.3 24.5
9 335.8 516.4 22.5
10 34G.G 5G7 30.4
11 339.9 529.7 23.4
12 332.4 569.8 37.9
13 330.9 520.0 52
14 3GG.1 585.9 28.7
15 3GG.1 585.9 28.7 l7 355.5 G05 59.4 18 344 5GG.4 27.7 19 339.8 585.4 39.2 Mcan 343.8 5G(1.2 35.1 b' ik
Claims (60)
1. Apparatus for depositing a layer of material on a surface, comprising:
means for delivering at an angle substantially normal to the surface a stream of material to a build-up area on the surface;
a plurality of lasers, each positioned with its axis at an acute angle to the normal to the surface, said lasers impinging on said build-up area on the surface to cause the material to adhere to the surface; and means for providing relative movement between the surface and both the delivering means and the lasers whereby the material is formed into a coating on the surface.
means for delivering at an angle substantially normal to the surface a stream of material to a build-up area on the surface;
a plurality of lasers, each positioned with its axis at an acute angle to the normal to the surface, said lasers impinging on said build-up area on the surface to cause the material to adhere to the surface; and means for providing relative movement between the surface and both the delivering means and the lasers whereby the material is formed into a coating on the surface.
2. Apparatus according to claim 1, wherein the material is in powder form.
3. Apparatus according to claim 1, wherein the material is in wire form.
4. Apparatus according to claim 1, wherein said lasers are at an angle of
5° to 45° to the normal to the surface.
. Apparatus according to claim 1, wherein a carrier directs the material through the tube.
. Apparatus according to claim 1, wherein a carrier directs the material through the tube.
6. Apparatus according to claim 1, wherein the lasers are positioned with their axis at an equal acute angle to the normal to the surface.
7. Apparatus according to claim 1, wherein the lasers are positioned with their axis equally spaced in the plane of the surface.
8. Apparatus according to claim 1, wherein said material is a metallic or ceramic powder.
9. Apparatus according to claim 1, wherein said material is a thin metal wire.
10. Apparatus according to claim 1, wherein the surface moves in its own plane.
11. Apparatus according to claim 1, wherein the size of the build-up area on the surface varies according to how the lasers are focused causing the width of the coating to be varied.
12. Apparatus according to claim 1, wherein the power of the lasers controls the power density within the build-up area.
13. Apparatus according to claim 1, wherein the laser is a Nd:YAG or CO2 laser.
14. Apparatus according to claim 1, wherein there are means for pre-heating and/or post heating the build-up area.
15. Apparatus according to claim 1 comprising an additional laser which impinges in advance of the build-up area or impinges behind the build-up area.
16. Apparatus according to claim 1 comprising one or more additional lasers impinging in advance of the build-up area and one or more additional lasers impinging behind the build-up area.
17. Apparatus for depositing a layer of material on a surface, comprising:
means for delivering at an angle substantially normal to the surface a stream of material in powder form to a build-up zone on the surface; a first laser positioned with its axis at an acute angle to the normal to the surface, said laser impinging on the build-up zone, a second laser positioned with its axis at a second acute angle to the normal to the surface, the second laser partially impinging the build-up zone in advance of the build-up zone or partially impinging the build-up zone behind the build-up zone, both lasers causing the material in powder form to fuse to the surface in the build-up zone; and means for moving the surface relative to both the delivering means and the lasers.
means for delivering at an angle substantially normal to the surface a stream of material in powder form to a build-up zone on the surface; a first laser positioned with its axis at an acute angle to the normal to the surface, said laser impinging on the build-up zone, a second laser positioned with its axis at a second acute angle to the normal to the surface, the second laser partially impinging the build-up zone in advance of the build-up zone or partially impinging the build-up zone behind the build-up zone, both lasers causing the material in powder form to fuse to the surface in the build-up zone; and means for moving the surface relative to both the delivering means and the lasers.
18. Apparatus according to claim 17, wherein additional lasers positioned with their axis at an acute angle to the normal to the surface partially impinge the build-up zone in advance of or behind the build-up zone.
19. Apparatus for depositing a layer of material on a surface, comprising:
means for delivering at a first acute angle to the normal to the surface a stream of material to a build-up area on the surface;
a laser positioned with its axis at a second acute angle to the normal to the surface, said laser impinging on said build-up area on the surface to cause the material to adhere to the surface; and means for providing relative movement between the surface and both the delivering means and the laser whereby the material is formed into a coating on the surface.
means for delivering at a first acute angle to the normal to the surface a stream of material to a build-up area on the surface;
a laser positioned with its axis at a second acute angle to the normal to the surface, said laser impinging on said build-up area on the surface to cause the material to adhere to the surface; and means for providing relative movement between the surface and both the delivering means and the laser whereby the material is formed into a coating on the surface.
20. Apparatus according to claim 19, wherein the material is in powder form.
21. Apparatus according to claim 19, wherein the material is in wire form.
22. Apparatus according to claim 19, wherein the laser is positioned with its axis in the plane containing the normal to the surface and the axis of the delivering means.
23. Apparatus according to claim 19, wherein the surface moves in its own plane.
24. Apparatus according to claim 19, wherein the first and second acute angles are between 5 ° and 45 ° to the normal to the surface.
25. Apparatus according to claim 19, wherein the first acute angle is 18°
to the vertical and wherein the second acute angle is 15 ° to the normal to the surface.
to the vertical and wherein the second acute angle is 15 ° to the normal to the surface.
26. Apparatus according to claim 19, wherein a carrier directs the material through the tube.
27. Apparatus according to claim 19, wherein there are means for pre-heating and/or post-heating the build-up area.
28. Apparatus according to claim 19, wherein another laser impinges ahead of the build-up area.
29. Apparatus according to claim 19, wherein another laser impinges behind the build-up area.
30. Apparatus according to claim 19, wherein said material is a metallic or ceramic powder.
31. Apparatus according to claim 19, wherein said material is a thin metal wire.
32. Apparatus according to claim 19, wherein the laser is a Nd: YAG or CO2 laser.
33. A method of depositing a coating of a material on a surface comprising the steps of delivering substantially along the normal to the surface a stream of material impacting an area on the surface; providing a plurality of lasers each at an acute angle to 22~
the normal to the surface, said lasers impinging said area causing the material to adhere to the surface; and moving the surface relative to both the stream of material and the lasers whereby the coating is formed on the surface.
the normal to the surface, said lasers impinging said area causing the material to adhere to the surface; and moving the surface relative to both the stream of material and the lasers whereby the coating is formed on the surface.
34. A method according to claim 33 wherein in the step of delivering the stream of material a carrier directs the material through a tube.
35. A method according to claim 33, wherein in the step of providing lasers said lasers are at an angle of 5° to 45° to the normal to the surface.
36. A method according to claim 33, wherein in the step of providing lasers the lasers are at equal acute angles to the normal to the surface.
37. A method according to claim 33, wherein in the step of providing lasers the lasers are provided equally spaced in the plane of the surface.
38. A method according to claim 33, wherein the steps are repeated so the lasers impinge a previously deposited coating and the stream of material to produce an additional coating bonded to the previously deposited coating.
39. A method according to claim 33, wherein in the step of delivering the stream of material said material is a metallic powder.
40. A method according to claim 33, wherein in the step of delivering the stream of material said material is a metal wire.
41. A method according to claim 33, wherein in the step of moving the surface relative to both the stream and the lasers, the surface is moved in its own plane.
42. A method of depositing a coating of a material on a surface comprising the steps of delivering at a first acute angle to the normal to the surface a stream of material impacting an area on the surface; providing one laser at a second acute angle to the normal to the surface, said laser impinging on said area causing the material to adhere to the surface; and moving the surface relative to both the stream of material and the laser whereby the coating is formed on the surface.
43. A method according to claim 42, wherein in the step of delivering the stream of material the material is in powder form.
44. A method according to claim 42, wherein in the step of delivering the stream of material the material is in wire form.
45. A method according to claim 42, wherein in the step of providing the laser, the laser is provided opposite to the stream in the plane containing the normal to the surface and the stream.
46. A method according to claim 42, wherein in the step of delivering the stream of material a carrier directs the material through the tube.
47. A method according to claim 42, wherein in the steps of delivering the stream of material and providing the laser the first and second acute angles are between 5° and 45°
to the normal to the surface.
to the normal to the surface.
48. A method according to claim 42, wherein in the steps of delivering the stream of material and providing the laser the first acute angle is 18° to the normal to the surface and wherein the second acute angle is 15° to the normal to the surface.
49. A method according to claim 42, wherein the steps are repeated to impinge a previously deposited coating and the stream of material producing an additional coating bonded to the previously deposited coating.
50. A method according to claim 42, wherein in the step of delivering the stream of material said material is a metallic powder.
51. A method according to claim 42, wherein in the step of delivering the stream of material said material is a metal wire.
52. A method according to claim 42, wherein in the step of moving the surface relative to both the stream and the laser, the surface is moved in its own plane.
53. A method of building up a dense metal part on a base plate comprising the steps of (a) depositing metal in powder or wire form in a delivery tube positioned with its axis substantially normal to the base plate to a build-up zone on the base plate; impinging the build-up zone with four Nd: YAG or CO2 lasers each positioned with its axis at an equal acute incident angle to the base plate, the lasers equally spaced in the plane of the base plate, said lasers melting the base plate and the metal in powder or thin wire form to create a fused metal layer; and moving the base plate along a path relative to both the tube and the lasers;
(b) repeating step (a) to heat and melt a thin layer of the previously deposited metal along with the metal powder or wire to form an additional layer metallurgically bonded to the fused metal layer; and (c) repeating step (b) to produce multiple layers until a metal part is formed along the path, said part having a substantially uniform height and width.
(b) repeating step (a) to heat and melt a thin layer of the previously deposited metal along with the metal powder or wire to form an additional layer metallurgically bonded to the fused metal layer; and (c) repeating step (b) to produce multiple layers until a metal part is formed along the path, said part having a substantially uniform height and width.
54. A method according to claim 53 including pre- and/or post- heating of the build-up zone on the base plate.
55. A method according to claim 53 including pre-heating the build-up zone with a laser directed at an area in advance of the build-up zone.
56. A method according to claim 53 including post-heating the build-up zone with a laser directed at an area behind the build-up zone causing the cooling rate to be controlled.
57. A method of building up a dense metal part on a base plate comprising the steps of (a) depositing metal in powder or wire form in a delivery tube positioned off axis at an acute incident angle to the base plate to a build-up area on the base plate; impinging the build-up area with a single Nd:YAG or CO2 laser at an acute off axis incident angle to the base plate, said laser in the same plane with the normal to the build-up area and the tube, said laser melting the base plate and the metal to create a layer of fused metal on the base plate; and moving the base plate along a path relative to both the tube and the lasers;
(b) repeating step (a) to heat and melt a thin layer of the previously deposited metal along with the metal powder or wire to form an additional layer metallurgically bonded to the fused metal layer; and (c) repeating step (b) to produce multiple layers until a metal part is formed along the path, sand part having a substantially uniform height and width.
(b) repeating step (a) to heat and melt a thin layer of the previously deposited metal along with the metal powder or wire to form an additional layer metallurgically bonded to the fused metal layer; and (c) repeating step (b) to produce multiple layers until a metal part is formed along the path, sand part having a substantially uniform height and width.
58. A method according to claim 57 including pre-heating and/or post-heating the build-up area.
59. A method according to claim 57 including pre-heating the build-up area with a laser directed at a point in advance of the build-up area.
60. A method according to claim 57 including post-heating the build-up area with a laser directed at a point behind the build-up area causing the cooling rate to be controlled.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US2577096P | 1996-09-23 | 1996-09-23 | |
| US60/025,770 | 1996-09-23 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2215940A1 CA2215940A1 (en) | 1998-03-23 |
| CA2215940C true CA2215940C (en) | 2006-06-13 |
Family
ID=21827973
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002215940A Expired - Lifetime CA2215940C (en) | 1996-09-23 | 1997-09-22 | Laser sintering apparatus for producing coatings and dense metal parts |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2215940C (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2186594A1 (en) * | 2008-11-12 | 2010-05-19 | Siemens Aktiengesellschaft | Method of and device for pre-heating during welding using a second laser beam |
| EP2377641A3 (en) * | 2010-04-16 | 2015-06-03 | Rolls-Royce plc | Method and apparatus for Manufacturing a Component |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6504127B1 (en) | 1999-09-30 | 2003-01-07 | National Research Council Of Canada | Laser consolidation methodology and apparatus for manufacturing precise structures |
| US6756561B2 (en) | 1999-09-30 | 2004-06-29 | National Research Council Of Canada | Laser consolidation apparatus for manufacturing precise structures |
| US20110056919A1 (en) * | 2008-02-13 | 2011-03-10 | Bernd Burbaum | Method for Fusing Curved Surfaces, and a Device |
| CN112281154B (en) * | 2020-09-27 | 2023-06-27 | 河南金源黄金矿业有限责任公司 | Technological method for repairing piston rod of release cylinder of double lasers |
-
1997
- 1997-09-22 CA CA002215940A patent/CA2215940C/en not_active Expired - Lifetime
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2186594A1 (en) * | 2008-11-12 | 2010-05-19 | Siemens Aktiengesellschaft | Method of and device for pre-heating during welding using a second laser beam |
| EP2377641A3 (en) * | 2010-04-16 | 2015-06-03 | Rolls-Royce plc | Method and apparatus for Manufacturing a Component |
Also Published As
| Publication number | Publication date |
|---|---|
| CA2215940A1 (en) | 1998-03-23 |
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