System and method for metal powder deposition using laser beam oscillation

Abstract

A method and system for laser metal powder deposition using beam oscillation can include a fiber laser configured to generate a laser beam, a laser head configured to receive the laser beam from the fiber laser and including a collimator configured to collimate the laser beam, an oscillation module having a first movable mirror and a second movable mirror, and a focusing lens configured to focus the collimated laser beam through a powder nozzle device such that a focal position of the focused, collimated laser beam is positioned below the workpiece surface. The powder nozzle device delivers metal powder to an area on the workpiece surface that is heated by the focused, collimated laser beam.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 62 / 963,600, entitled "SYSTEM AND METHOD FOR METAL POWDER DEPOSITION USING LASER BEAM WOBBLING," filed January 21, 2020, which is incorporated herein by reference in its entirety.

[0002] The technical field relates generally to metal powder deposition, and more particularly to a fiber laser system and method for depositing metal powder onto a workpiece surface using oscillation of a laser beam. [Background technology]

[0003] Laser metal deposition (LMD) is an additive technique that involves using a laser beam to form a pool of molten metal (molten pool) on the surface of a metal substrate, where metal powder is impinged via a gas stream. The metal powder is drawn into the molten pool (i.e., melted and bonded to the substrate), producing deposits on the surface of the substrate. These deposits can be used to build or repair metal parts in many different applications. For example, LMD is applicable to several areas of industrial use, including surface coating, repair welding, and general manufacturing, particularly for mold, tool, and part-type applications. Coating materials include metal alloys (e.g., Co, Ni, Cu substrates, Ti, and steel), hard metals (e.g., carbides), and ceramics. Base metal materials include steel, cast iron, bronze, and metal alloys.

[0004] LMD has the ability to coat softer metals, resulting in a hard, high-quality surface using a metallurgical bond, as opposed to the mechanical bond created using spray welding or plating techniques. Substrates with desired thermal insulation properties can be coated with conductive layers or other layers that are resistant to environmental influences such as high (low) temperatures, salt, water, and / or chemicals. LMD processing methods offer many advantages, including low and controlled heat input (i.e., LMD transfers less heat to the substrate material than many conventional techniques) and rapid cooling rates, making it possible to create sophisticated microstructures with minimal dilution and heat-affected zones (HAZ). These attributes minimize defects caused by stress and strain. LMD also offers economic benefits, such as faster manufacturing times and lower costs. However, even with these advantages, many applications exist that require faster deposition rates and improved process control and stability, tooling flexibility, and dilution control. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Patent Application No. PCT / US2015 / 45037 [Patent Document 2] International Patent Application No. PCT / US2019 / 064521 [Patent Document 3] U.S. Patent Application Serial No. 15 / 187,235 [Patent Document 4] U.S. Patent No. 10,751,835 Summary of the Invention [Means for solving the problem]

[0006] Aspects and embodiments are directed to systems and methods for metal powder deposition using laser beam oscillation. According to one embodiment, a system for laser metal powder deposition is provided. The system includes: a fiber laser configured to generate a laser beam; a laser head configured to receive the laser beam from the fiber laser and a collimator configured to collimate the laser beam; an oscillation module having first and second movable mirrors, the first and second movable mirrors being approximately the same size and configured to receive the collimated laser beam from the collimator and oscillate the parallel laser beam on first and second axes within a scan angle of approximately 0.1 to 2 degrees; and a focusing lens, not a scan lens, configured to focus the parallel laser beam, wherein the focused parallel laser beam is directed through a powder nozzle device such that a focal position of the focused parallel laser beam is positioned below the workpiece surface. The powder nozzle device is configured to deliver metal powder to an area on the workpiece surface heated by the focused parallel laser beam.

[0007] In certain embodiments, the system is configured to provide a metal powder deposition rate of at least 1 kg / hr.

[0008] According to at least one embodiment, the focal position of the focused, parallel laser beam is within a range of 1 mm to 30 mm below the workpiece surface, and according to yet a further embodiment, the focal position is within a range of 5 mm to 20 mm below the workpiece surface.

[0009] In some embodiments, the metal powder is a nickel-based superalloy. In further embodiments, the workpiece is a glass mold.

[0010] According to certain embodiments, the laser beam produced by the fiber laser has a power of at least 0.3 kW.

[0011] According to another embodiment, the oscillating module is configured to oscillate the collimated laser beam in a repeating oscillating pattern over the surface of the workpiece in coordination with the movement of at least one of the workpiece and the laser head, hi some embodiments, the oscillating pattern has a diameter having a maximum value of about 6 mm.

[0012] According to another aspect of the present invention, there is provided a metal powder deposition method. According to one embodiment, the method includes providing a fiber laser configured to generate a laser beam, collimating the laser beam by passing the laser beam through a collimator, providing an oscillating module having first and second movable mirrors of approximately the same size, the oscillating module configured to receive the collimated laser beam and oscillate the collimated laser beam in first and second axes within a scan angle of approximately 0.1 to 2 degrees, directing the laser beam through a focusing lens, rather than a scanning lens, configured to focus and direct the collimated laser beam through a powder nozzle device such that the focused, collimated laser beam has a focal position below the workpiece surface, and using the focused, collimated beam to heat an area on the workpiece surface where metal powder delivered by the powder nozzle device impinges.

[0013] According to some embodiments, the method further includes moving the first movable mirror and the second movable mirror to oscillate the parallel laser beam in a repeating oscillating pattern within the opening of the powder nozzle device. According to one embodiment, the oscillating pattern has a diameter having a maximum value of 6 mm.

[0014] In certain embodiments, the method further includes providing a laser head including a collimator, an oscillating module, and a focusing lens.

[0015] In some embodiments, the fiber laser is configured to have a power of at least 0.3 kW. In some embodiments, a method includes providing a fiber laser.

[0016] According to certain embodiments, the method further includes adjusting at least one component of the laser head so that the focal position is within a range of about 1-30 mm below the workpiece surface. According to other embodiments, the focal position is adjusted to be within a range of about 5-20 mm below the workpiece surface.

[0017] According to at least one embodiment, the method includes oscillating a collimated laser beam in coordination with movement of at least one of the workpiece and the laser head.

[0018] According to one embodiment, the method includes controlling the fiber laser and the oscillating module to provide a deposition rate of the metal powder of at least 1 kg / hr.

[0019] In some embodiments, the workpiece is a glass mold and the metal powder is a nickel-based superalloy.

[0020] Further aspects, embodiments, and advantages of these exemplary aspects and embodiments are discussed in detail below. Furthermore, it should be understood that both the above information and the following detailed description are merely specific examples of various aspects and embodiments and are intended to provide an overview or framework for understanding the nature and characteristics of the claimed aspects and embodiments. The implementations disclosed herein may be combined with other embodiments, and references to "an embodiment," "an example," "some embodiments," "some examples," "alternative embodiments," "various embodiments," "one embodiment," "at least one embodiment," "this and other embodiments," "certain embodiments," etc. are not necessarily mutually exclusive and are intended to indicate that a particular feature, structure, or characteristic described may be included in at least one embodiment. Appearances of such terms herein do not necessarily all refer to the same embodiment.

[0021] Various aspects of at least one embodiment are discussed below with reference to the accompanying drawings, which are not intended to be drawn to scale. The figures are included to provide an explanation and further understanding of various aspects and embodiments, and are incorporated into and constitute a part of this specification, but are not intended to define limitations to any particular embodiment. The drawings, together with the remainder of the specification, serve to explain the principles and operation of the described and claimed aspects and embodiments. In the figures, each identical or nearly identical component shown in various figures is represented by a like numeral. For clarity, not every component in every figure may be labeled. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic block diagram of an example of a system for laser metal powder deposition, according to one or more embodiments of the present invention. [Figure 2] 1 is a schematic diagram of an oscillating laser beam within the opening of a nozzle, in accordance with one or more embodiments of the present invention. [Figure 3] 2 is a schematic diagram of a collimated laser beam focused by a focusing lens to a focal position below a workpiece surface, in accordance with an aspect of the present invention; [Figure 4A] 1 is a schematic diagram illustrating one wobble pattern that can be generated by a laser head including a wobble module, according to an embodiment of the present invention. [Figure 4B] 1 is a schematic diagram illustrating one wobble pattern that can be generated by a laser head including a wobble module, according to an embodiment of the present invention. [Figure 4C] 1 is a schematic diagram illustrating one wobble pattern that can be generated by a laser head including a wobble module, according to an embodiment of the present invention. [Figure 4D] 1 is a schematic diagram illustrating one wobble pattern that can be generated by a laser head including a wobble module, according to an embodiment of the present invention. [Figure 5] FIG. 2 is a schematic diagram of another example of a system for laser metal powder deposition, in accordance with an aspect of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] The disclosed exemplary systems and methods can be used to deposit metal powder using laser beam oscillation. This approach can improve the performance of LMD processes over traditional LMD processes and is applicable to several areas, such as processes involving part repair (e.g., molds, turbine blades, etc.), surface hardening, coatings, or deposition of alloys onto base materials to improve surface corrosion resistance, wear resistance, friction properties, etc., as well as deposition processes related to additive manufacturing.

[0024] The disclosed technique is a type of LMD process that offers several advantages over existing LMD processes, including faster deposition rates, improved process stability, tool flexibility, and dilution control, as well as control of cooling and / or heating rates. For example, oscillating the laser beam of the deposition process increases process stability by reducing the sensitivity variation between the nozzle standoff and the focal position relative to the workpiece surface. Using the oscillation deposition technique, deposition rates of several kg / hour can be achieved. In addition, the oscillation pattern, amplitude, and frequency can be adjusted for different surfaces (e.g., shapes, surface structures, surface materials, etc.), thereby increasing the flexibility of the system. For example, adjusting the oscillation pattern, amplitude, and / or frequency can slow (or increase) the deposition rate in one or more regions of the workpiece. The beam oscillation implemented by the oscillation aspect of the present invention also provides better control of dilution, i.e., optimizing the dilution of the material-added layer. High dilution results in too much laser power being used to remelt the substrate, which can result in overheating, while low dilution results in insufficient bonding to the substrate and even lack of fusion. Furthermore, laser deposition using beam oscillation improves control of cooling and heating rates, reducing the need for post-weld heat treatment (PWHT). Residual stresses and distortions caused by the deposition process are also reduced using oscillation deposition compared to conventional coating processes.

[0025] 1 illustrates a system for laser metal deposition, generally designated 100. For example, system 100 can be used to deposit a metal material on a workpiece 145. System 100 includes a fiber laser 105 configured to generate a laser beam capable of propagating in an output fiber 107, and a laser head 110 configured to receive the laser beam from fiber laser 105. Laser head 110 includes a collimator 115, an oscillating module 120 having a first movable mirror 122 and a second movable mirror 124, and a focusing lens 130.

[0026] The workpiece 145 can be constructed from any one of several different materials, depending on the desired application. Non-limiting examples of substrates from which the workpiece 145 can be constructed include metallic materials such as steel, cast iron, bronze, carbides, and metal alloys, as well as superalloys such as Inconel. The workpiece may be a component (e.g., a glass mold) that is resistant to high temperature (heat) capabilities and / or corrosion (oxidation, acid, alkali, and salt), and / or other chemical resistance applications, such as components in oil and gas drilling, refining, storage, and distribution. According to one embodiment, the workpiece 145 is a glass mold. Such molds are typically made of a base metallic material and are used to make glass objects, such as lenses.

[0027] The fiber laser 105 may include an ytterbium (Yb) fiber laser capable of generating a laser in the near-infrared spectral range (e.g., a center wavelength ranging from approximately 1030 to 1080 nm). Other fiber lasers, including Yb fiber lasers, erbium lasers, thulium lasers, and green lasers in the 978 to 1020 nm range, are also within the scope of this disclosure, and in some cases, the visible wavelength range is also possible. According to at least one embodiment, the laser beam generated by the fiber laser 105 may have a power of at least 0.5 kW, and according to one embodiment, a minimum power of approximately 0.3 kW. Higher laser powers up to 10 kW are also achievable, and in some cases, the laser power may range between 16 and 20 kW. The fiber laser may be configured to emit single-mode or multimode light and may operate in continuous or pulsed mode. Non-limiting examples of suitable fiber lasers include the YLS series lasers available from IPG Photonics Corporation. The fiber laser 105 can also include an adjustable mode beam (AMB) laser, such as the YLS-AMB series of lasers available from IPG Photonics. The fiber laser 105 can also include a multi-beam fiber laser, such as the type disclosed in U.S. Patent No. 5,623,999, entitled "MULTIBEAM FIBER LASER SYSTEM," which is capable of selectively delivering one or more laser beams through multiple fibers, and U.S. Patent No. 5,623,999, entitled "ULTRAHIGH FIBER LASER SYSTEM WITH CONTROLLABLE OUTPUT BEAM INTENSITY PROFILES," which describes a system comprised of multiple fiber lasers capable of simultaneously or sequentially delivering beams with different intensity distribution profiles (e.g., central and / or donut-shaped). It should be understood that, in addition to fiber lasers, other types of solid-state laser sources, such as, for example, Nd:YAG lasers, are also within the scope of this disclosure.

[0028] The collimator 115 is configured to collimate the laser beam from the fiber laser 105. The collimator 115 includes one or more collimating optical elements, such as a collimator lens, that collimate the laser beam, as will be understood by those skilled in the art. A collimated laser beam 117 is output by the collimator 115. According to some embodiments, the collimator 115 can also include one or more optical elements, such as a movable lens, that can adjust the beam spot size and / or focus.

[0029] The oscillating module 120 is disposed downstream from the collimator 115 and is configured to receive the parallel laser beam 117 from the collimator 115. The oscillating module 120 includes a first movable mirror 122 and a second movable mirror 124. The first movable mirror 122 is disposed upstream from the second movable mirror 124. The first movable mirror 122 and the second movable mirror 124 are configured to reflect and move the parallel laser beam, i.e., to oscillate the parallel laser beam about a first axis and a second axis, respectively. The first movable mirror 122 reflects the parallel laser beam toward the second movable mirror 124, which in turn reflects the parallel laser beam toward the focusing lens 130. The first movable mirror 122 and the second movable mirror 124 are pivotable about different axes (i.e., the x-axis and the y-axis) to move the parallel laser beam 117, and therefore the focused (and parallel) laser beam 155, relative to the workpiece 145 in at least two different perpendicular axes. The movable mirrors 122, 124 may be galvanometer mirrors (also referred to herein as galvanometers), each movable by galvo motors 125a, 125b, respectively, controlled by a controller 150. Galvo motors are capable of rapidly reversing direction. In other embodiments, other mechanisms, such as stepper motors, can be used to move the mirrors. The use of movable mirrors 122, 124 allows for beam oscillation without having to move the entire laser head 110 or use a rotating prism.

[0030] According to at least one embodiment, the first movable mirror 122 and the second movable mirror 124 move the focused laser beam 155 within a scan angle in the range of 0.1 to 2 degrees. For example, the controller 150 controls the movable mirrors 122, 124 to pivot the beam 155 within a scan angle alpha (α) of approximately 0.1 to 2 degrees, thereby enabling the beam to oscillate, as shown in FIG. 2 . According to various embodiments, the oscillation diameter (i.e., the diameter of the oscillation pattern) has a maximum value of approximately 6 mm, and in some embodiments, is approximately 3 mm. However, it should be understood that the oscillation diameter may be smaller or larger than these stated values ​​in certain applications. In certain cases, the oscillation diameter is a function of (or limited by) the diameter of the nozzle orifice / opening. This limited beam motion (i.e., oscillation diameter) contrasts with conventional laser scan heads, which typically achieve laser beam motion within a much larger field of view (e.g., as large as 50x50 mm and 250x250 mm) and are therefore designed to accommodate larger fields of view and scan angles. Thus, the use of movable mirrors 122, 124 achieves only relatively small beam motion, which is contrary to conventional wisdom that achieves a wider field of view when using galvanometer scanners. By limiting the scan angle and beam motion, advantages can be realized, such as faster speeds, the ability to use less expensive components such as lenses, and the use of certain accessories, such as gas assist accessories that provide shielding gas for certain applications. The smaller beam motion and scan angle also allows the second movable mirror 124 to be approximately the same size as the first movable mirror 122. In contrast, conventional galvanometer scanners typically use a larger second mirror to achieve a larger field of view and scan angle, which limits the speed of motion in at least one axis.Therefore, the smaller size of the second movable mirror 124 (e.g., approximately the same size as the first movable mirror 122) in the oscillating module 120 and laser head 110 allows the second movable mirror 124 to move at a faster speed compared to larger mirrors in conventional galvanometer scanners that achieve large scan angles.

[0031] According to one embodiment, the oscillating module 120 is configured to oscillate the parallel laser beam 117 in a repeating oscillating pattern over the surface of the workpiece 145 in coordination with the movement of at least one of the workpiece 145 and the laser head 110. FIGS. 4A-4D illustrate examples of oscillating patterns that can be used in the laser deposition methods described herein. As used herein, the term "oscillating" refers to the reciprocating motion of the laser beam in two axes with mirrors configured to implement a scan angle of approximately 0.1-2°. FIG. 4A illustrates a clockwise or counterclockwise circular pattern, FIG. 4B illustrates a linear pattern, FIG. 4C illustrates a figure-eight pattern, and FIG. 4D illustrates an infinite pattern. As will be appreciated, these oscillating patterns are non-limiting and other patterns are within the scope of the present disclosure. Aspects of the oscillating module 120 are described in U.S. Patent Application Publication No. 2007 / 0129994, now U.S. Patent Application Publication No. 2007 / 0129994, which are owned by the applicant and are incorporated herein by reference in their entireties.

[0032] 1 , laser head 110 and / or workpiece 145 can move relative to one another using a motion mechanism, such as a motion stage. For example, laser head 110 can be positioned on motion stage 142 to move laser head 110 relative to the workpiece along at least one axis. Additionally or alternatively, workpiece 145 can be positioned on motion stage 144 to move workpiece 145 relative to laser head 110. Both stages 142 and 144 can be controlled by controller 150.

[0033] Laser head 110 also includes focusing lens 130. Focusing lens 130 is not a scanning lens, in contrast to conventional laser scan heads that employ the use of multi-element scanning lenses, such as F-theta lenses, field-flattening lenses, and / or telecentric lenses, which have much larger diameters to focus the beam within a larger field of view. Because first movable mirror 122 and second movable mirror 124 move the beam within a relatively small field of view, a larger multi-element scanning lens is not necessary or used. The use of a smaller lens also allows for additional accessories, such as an air knife and / or gas assist accessories, to be used at the end of the laser head. Focusing lens 130 may have a variety of focal lengths, for example, ranging from 100 mm to 1000 mm.

[0034] The focusing lens 130 is configured to focus the parallel laser beam 117 such that the focal point 132 of the focused parallel laser beam 155 is positioned below the workpiece surface 147, as shown in FIG. 3 . The inventors have discovered that by positioning the focal point below the workpiece surface, better deposition results are achieved than when the focal point is at or above the surface. According to some embodiments, the focal point location may be within a range of 1-30 mm below the workpiece surface, and in some cases, 5-20 mm below the workpiece surface. It should be understood that the optimal distance of the focal point below the workpiece surface depends on several factors, non-limiting examples of which include the thickness and material type of the substrate, the desired deposition rate, and the characteristics of the metal powder (e.g., powder material, powder size, etc.).

[0035] According to at least one embodiment, the position of focal spot 132 can be adjusted by having controller 150 control the position of one or more components in laser head 110, such as focusing lens 130, by moving the focusing lens up or down in the z-axis direction, as shown by the arrows in FIG. 3. In other embodiments, laser head 110 can be moved via motion stage 142 and / or workpiece 145 can be moved via motion stage 144, which are controlled by controller 150. In yet other embodiments, one or more components of collimator 115 can be adjusted to move the position of focal spot 132.

[0036] Returning again to FIG. 1 , the focused, parallel laser beam 155 is directed through a powder nozzle device 135 configured to supply metal powder to an area on the workpiece surface 147 (see FIG. 3 ) that is heated by the focused, parallel laser beam 155. The metal powder can be supplied to the powder nozzle device 135 by a metal powder supply 136. The powder nozzle device 135 can be attached to the laser head 110 and configured to be coaxial with the focused, parallel laser beam 155. For example, the powder nozzle device 135 has an aperture 138 through which the focused, parallel laser beam 155 propagates (and oscillates). According to some embodiments, the aperture 138 has a maximum diameter of about 6 mm, although larger diameters are still within the scope of the present disclosure. Non-limiting examples of coaxial nozzles include the coaxial powder nozzle developed by Fraunhofer, or similar devices. In some cases, a cooling system is incorporated with the powder nozzle device 135 for temperature control.

[0037] Depending on the desired application, the metal powder may be any one of a metal alloy (e.g., Co, Ni, Cu substrate, Ti and steel), a metal superalloy (e.g., nickel-based superalloys such as Inconel, Hastelloy, Waspaloy, Rene alloys, etc.), or a hard metal (e.g., carbide).

[0038] As discussed above, implementing laser oscillation as part of an LMD method and system increases deposition rates over LMD configurations that do not include laser beam oscillation. According to at least one embodiment, system 100 is configured for metal powder deposition rates of at least 1 kg / hr, and in some embodiments, deposition rates of several kg / hr, e.g., 2-5 kg / hr, can be achieved, and in some applications, deposition rates can exceed 5 kg / hr. As one non-limiting example, an alloy similar to Inconel 625 was deposited at a rate of approximately 4 kg / hr using a 4 kW laser. These deposition rates contrast with conventional LMD systems not configured with laser beam oscillation, which typically have deposition rates of 0.5-0.8 kg / hr. It should be understood that, for example, in applications depositing oxide materials, deposition rates below 1 kg / hr are still within the scope of the present disclosure. Lower deposition rates may also be within the scope of certain types of applications, such as high velocity oxygen fuel (HVOF) coating. The fiber laser 105 and the oscillation module 120 can be controlled by the controller 150 to achieve these enhanced deposition rates. The oscillation capability also enhances the flexibility of the LMD system 100 because at least one of the oscillation pattern, frequency, and oscillation amplitude can be adjusted to achieve different deposition rates. In some embodiments, by using different oscillation process parameters (e.g., oscillation pattern, frequency, amplitude), multiple (different) deposition rates can be used in a single deposition process. Such an approach may also include using a stationary laser spot to achieve very low deposition rates. According to one embodiment, the oscillation frequency is in the range of 50 to 1000 Hz, and the oscillation amplitude is in the range of 0.5 mm to 12 mm. According to one embodiment, the LMD system 100 is capable of achieving a coating speed of 0.2 to 4 m / min.

[0039] According to some embodiments, the deposition rate results in an overlap thickness of at least 1 mm, and in some cases may be at least 2 mm, although it should be understood that thinner overlap thicknesses (e.g., less than 1 mm) are still within the scope of this disclosure and may depend on the specific application (e.g., during oxide deposition and / or HVOF coating). As will be appreciated, multiple passes may be performed to achieve the desired thickness. Additionally, the use of LMD with laser beam oscillation further minimizes or otherwise reduces dilution compared to LMD systems that do not include laser beam oscillation. Low dilution means that very little substrate mixes with the coating, leaving a surface layer of the coating that is very close to the pure coating material.

[0040] Controller 150 is configured to control one or more components of LMD system 100. As shown in FIG. 1 , controller 150 is configured to communicate with fiber laser 105, laser head motion stage 142, workpiece motion stage 144, first and second movable mirrors 122 and 124, focusing lens 130, and powder supply / powder feed 136 (which may also include powder nozzle device 135). For example, the positioning of movable mirrors 122, 124 and / or motion stages 142, 144 may be controlled by controller 150. Additionally, controller 150 may also control laser parameters, such as laser power, and oscillation process parameters, such as oscillation pattern, frequency, and amplitude. In some cases, controller 150 may be configured to operate according to a preset or predetermined motion control scheme, while in other cases, controller 150 may be configured to operate in a feedforward or feedback control scheme using information obtained from one or more cameras or sensors or other input sources (e.g., an operator), and thus may be operatively coupled to these input sources. Non-limiting examples of input sources are discussed below. Controller 150 includes hardware (e.g., a general-purpose computer) and software that can be used to control the components of the system. It will be understood that more than one controller or control device can be used.

[0041] The system 100 may also include one or more detectors, such as a camera and / or sensors, to provide various feedback data to the controller 150. For example, one or more process parameters, such as powder injection parameters, laser power, feed rate, temperature, coating (overlay) thickness, level of dilution, and laser surface parameters, such as substrate thickness or substrate surface condition, may be monitored.

[0042] Although not explicitly shown, according to another embodiment, laser head 110 may also include a fixed mirror that can be used to direct the collimated laser beam 117 to focusing lens 130. The use of a fixed mirror can be used in some applications where a laser head with a smaller footprint is desirable.

[0043] Other optical components may also be used in the laser head 110. For example, FIG. 5 illustrates a system 500 for an LMD similar to the system 100 of FIG. 1 , but in this example, the laser head 510 also includes a beam shaping module 540 positioned between the collimator 115 and the oscillating module 120. The beam shaping module 540 is configured to receive and shape the parallel laser beam 117. For example, the beam shaping module 540 may receive an input beam having a Gaussian shape and a circular beam spot and may include at least one beam-shaping diffractive optical element to shape the beam. Non-limiting examples of beam shapes that may be implemented using the beam shaping module 540 include a “top hat,” ellipse, rectangle, square, and ring shape. One or more components of the beam shaping module 540 may also be controlled by the controller 150.

[0044] Some embodiments of the invention provide a method including providing a fiber laser configured to generate a laser beam; collimating the laser beam by passing the laser beam through a collimator; providing an oscillating module having first and second movable mirrors of approximately the same size, the oscillating module configured to receive the collimated laser beam and oscillate the collimated laser beam in first and second axes within a scan angle of approximately 0.1-2°; directing the laser beam through a focusing lens, rather than a scanning lens, configured to focus and direct the collimated laser beam through a powder nozzle device such that the focused, collimated laser beam has a focal position that is below the workpiece surface; and using the focused, collimated beam to heat an area on the workpiece surface where metal powder delivered by the powder nozzle device impacts.

[0045] Some embodiments of the method further include moving the first and second movable mirrors to oscillate the parallel laser beam in a repeating oscillating pattern within the opening of the powder nozzle device, hi some embodiments, the oscillating pattern has a diameter having a maximum value of about 6 mm.

[0046] Some embodiments of the method further include providing a laser head including a collimator, an oscillating module, and a focusing lens.

[0047] Some embodiments of the method further include providing a fiber laser, hi some embodiments, the fiber laser is configured to have a power of at least 0.3 kW.

[0048] Some embodiments of the method further include adjusting at least one component of the laser head so that the focal position is within a range of about 1 to 30 mm below the workpiece surface, hi some embodiments, the focal position is adjusted to be within a range of about 5 to 20 mm below the workpiece surface.

[0049] Some embodiments of the method further include oscillating the collimated laser beam in coordination with the movement of at least one of the workpiece and the laser head.

[0050] Some embodiments of the method further include controlling the fiber laser and the oscillating module to deposit the metal powder at a deposition rate of at least 1 kg / hr. In some embodiments, the workpiece is a glass mold and the metal powder is a nickel-based superalloy.

[0051] As noted above, LMD with laser beam wobble offers several advantages over LMD processes without the ability to wobble. For example, wobble reduces the sensitivity variation between the nozzle standoff and the focal position relative to the workpiece surface; i.e., wobble increases the technical depth of field of the system compared to LMD configurations that do not include beam wobble.

[0052] LMD with laser beam oscillation can also improve control of the heating and cooling rates of the deposition process. That is, heat input can be controlled much more easily than in systems without oscillation capabilities. For example, superalloys are prone to microcracks during localized heating. Oscillating the laser beam during deposition allows for better control of heat input. For example, oscillation prevents the formation of hot spots, which allows for better homogenization of the alloy's constituents. This results in a reduction of residual stresses and distortions that may be introduced by the deposition process.

[0053] The disclosed process also reduces the effects of heat-affected zones (HAZ), i.e., results in smaller HAZ. For example, deposition of an alloy on a substrate or base creates a region just below the weld / base interface where the base material did not melt, but the local temperature increased to a point where its microstructure and therefore material properties changed. This region is known as the HAZ. These changes to material properties are typically undesirable and can impair the function and / or life of the component, as microstructural changes can result in reduced strength, increased brittleness, or reduced corrosion resistance. Some non-limiting technical reasons why the introduction of oscillation technology into the coating process can reduce HAZ include the ability of beam oscillation to create a mixing effect, resulting in a more homogeneous chemical composition of the molten material; the ability of beam oscillation to increase the "virtual velocity" of the laser, thereby avoiding localized overheating in the material; and the ability of beam oscillation to distribute the laser's power over a larger surface, thereby increasing the overall heat input so that rapid heating or cooling is avoided. Thus, the oscillation allows the available laser power to be optimized to increase productivity, while still not adversely affecting material quality.

[0054] It should be understood that while the systems and methods described above relate to metal powder deposition using a coaxial nozzle, other configurations including offline powder nozzles (e.g., pre-positioned coating processes) and wire feed systems are also within the scope of the present disclosure.

[0055] Aspects disclosed herein in accordance with the present invention are not limited to the details of construction and the arrangement of components in their application as set forth in the following description or illustrated in the accompanying drawings. These aspects may assume other embodiments and be practiced or carried out in various ways. Examples of specific implementations are provided herein for illustrative purposes only and are not intended to be limiting. In particular, acts, components, elements, and features discussed in connection with any one or more embodiments are not intended to be excluded from a similar role in any other embodiment.

[0056] Additionally, the phrases and terms used herein are for descriptive purposes and should not be considered limiting. Any reference herein to system and method examples, embodiments, components, elements, or acts in the singular can also include embodiments that include the plural, and any reference herein to any embodiment, component, element, or act in the plural can also include embodiments that include only the singular. References in the singular or plural are not intended to limit the systems or methods, their components, acts, or elements disclosed herein. The use herein of "including," "comprising," "having," "containing," "involving," and variations thereof, is meant to encompass the items listed thereafter and equivalents thereof, as well as additional items. References to "or" can be interpreted as inclusive, such that any item described using "or" can refer to any of one, more than one, and all of the listed items. Additionally, in the event of a discrepancy in terminology between this document and a document incorporated herein by reference, the terminology in the incorporated reference is supportive of that of this document, and in the event of an irreconcilable discrepancy, the terminology in this document shall control.

[0057] Having thus described several aspects of at least one example, it should be understood that various alterations, modifications, and improvements will readily occur to those skilled in the art. For example, the examples disclosed herein can be used in other contexts. Such alterations, modifications, and improvements are intended to be part of this disclosure and are intended to be within the scope of the examples discussed herein. Accordingly, the foregoing description and drawings are by way of example only. [Explanation of symbols]

[0058] 100 systems 105 Fiber laser 107 Output Fiber 110 Laser Head 115 Collimator 117 Parallel laser beam 120 Swing Module 122 First moving mirror 124 Second moving mirror 125a Galvano Motor 125b Galvano Motor 130 focusing lens 132 Focus 135 Powder Nozzle Device 136 Metal powder supply section 138 Aperture 142 Motion Stage 144 Workpiece Motion Stage 145 Workpiece 147 Workpiece surface 150 Controller 155 Focused parallel laser beam 500 Systems 510 laser head 540 Beam Shaping Module

Claims

1. 1. A system for laser metal powder deposition, comprising: a fiber laser configured to generate a laser beam; a laser head configured to receive the laser beam from the fiber laser; a collimator configured to collimate the laser beam; an oscillating module having a first movable mirror and a second movable mirror, the first movable mirror and the second movable mirror being approximately the same size and configured to receive the parallel laser beam from the collimator and oscillate the parallel laser beam about a first axis and a second axis within a scan angle of 0.1 to 2 degrees; a focusing lens, not a scanning lens, configured to focus the parallel laser beam, the focused parallel laser beam being directed through a powder nozzle device such that a focal position of the focused parallel laser beam is positioned below a workpiece surface; and a laser head including: Equipped with The system, wherein the powder nozzle device is configured to supply metal powder to an area on the workpiece surface that is heated by the focused, collimated laser beam.

2. The system of claim 1 configured to provide a metal powder deposition rate of at least 1 kg / hr.

3. 10. The system of claim 1, wherein the focal position of the focused, collimated laser beam is within a range of 1 mm to 30 mm below the workpiece surface.

4. The system of claim 3, wherein the focal position is within a range of 5 to 20 mm below the workpiece surface.

5. The system of claim 1 , wherein the metal powder is a nickel-based superalloy.

6. The system of claim 5 , wherein the workpiece is a glass mold.

7. 10. The system of claim 1, wherein the laser beam produced by the fiber laser has a power of at least 0.3 kW.

8. 2. The system of claim 1, wherein the oscillating module is configured to oscillate the parallel laser beam in a repeating oscillating pattern over the workpiece surface in coordination with movement of at least one of the workpiece and the laser head.

9. The system of claim 8 , wherein the repeating rocking pattern has a diameter having a maximum value of 6 mm.

10. providing a fiber laser configured to generate a laser beam; collimating the laser beam by passing the laser beam through a collimator; providing an oscillating module having first and second movable mirrors of approximately the same size, the oscillating module configured to receive the parallel laser beam and oscillate the parallel laser beam about a first axis and a second axis within a scan angle of 0.1° to 2°; directing the laser beam through a focusing lens, rather than a scan lens, configured to focus and direct the parallel laser beam through a powder nozzle device such that the focused, parallel laser beam has a focal position below a workpiece surface; using the focused, collimated beam to heat an area on the workpiece surface where metal powder delivered by the powder nozzle device impinges; 1. A laser metal powder deposition method comprising:

11. 11. The method of claim 10, further comprising moving the first movable mirror and the second movable mirror to oscillate the parallel laser beam in a repeating oscillating pattern within the opening of the powder nozzle device.

12. 12. The method of claim 11, wherein the repeating rocking pattern has a diameter having a maximum value of 6 mm.

13. The method of claim 10 further comprising providing a laser head including the collimator, the oscillating module, and the focusing lens.

14. The method of claim 13 , wherein the fiber laser is configured to have a power of at least 0.3 kW.

15. The method of claim 14 further comprising providing the fiber laser.

16. 14. The method of claim 13, further comprising adjusting at least one component of the laser head so that the focal position is within a range of 1 mm to 30 mm below the workpiece surface.

17. 17. The method of claim 16, wherein the focal position is adjusted to be within a range of 5 mm to 20 mm below the workpiece surface.

18. The method of claim 13 , further comprising the step of oscillating the collimated laser beam in coordination with the movement of at least one of the workpiece and the laser head.

19. The method of claim 10 , further comprising controlling the fiber laser and the oscillating module so that the metal powder deposition rate is at least 1 kg / hr.

20. The method of claim 10 , wherein the workpiece is a glass mold and the metal powder is a nickel-based superalloy.

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