PATENT DOCUMENT

Publication Number: US-8733422-B2
Application Number: US-201213430221-A
Country: US
Kind Code: B2

Title: Laser cladding surface treatments

Abstract:
A metal enclosure has a surface region which is coated with cladding material using a laser cladding process. The metal enclosure can form at least a portion of an electronic device housing. All or part of one or more surfaces of the enclosure can be coated with cladding material. The coating of cladding material can be varied at selective regions of the enclosure to provide different structural properties at these regions. The coating of cladding material can be varied at selective regions to provide contrast in cosmetic appearance.

Claims:
What is claimed is: 
     
       1. A method comprising:
 providing a metal enclosure forming at least a portion of an electronic device housing, the metal enclosure including a first external surface region and a second external surface region; 
 performing a first laser cladding process on the first external surface region, wherein the first external surface region is coated with a first cladding material to form a first cladded region; and 
 performing a second laser cladding process on the second external surface region, wherein the second external surface region is coated with a second cladding material to form a second cladded region. 
 
     
     
       2. The method of  claim 1 , further comprising performing a finishing process on the first or second cladded regions. 
     
     
       3. The method of  claim 2 , wherein the finishing process is chosen from polishing, blasting, sanding, tumbling, brushing, electropolishing, chemical polishing, and any combination thereof. 
     
     
       4. The method of  claim 1 , wherein the metal enclosure is a finished metal enclosure in which a finishing process was performed on the first and second surface regions of the metal enclosure prior to the step of performing a laser cladding process on the first and second surface regions. 
     
     
       5. The method of  claim 1 , wherein the first external surface region is a groove in the metal enclosure, and wherein the first cladded region is an inlaid-cladding region, wherein the step of performing the first laser cladding process comprises filling the groove with the first cladding material to form the inlaid-cladding region. 
     
     
       6. The method of  claim 5 , wherein the first cladded region has a structural property chosen from corrosion resistance, hardness, and fracture toughness, wherein the structural property is greater than a corresponding structural property of an underlying surface region. 
     
     
       7. The method of  claim 1 , further comprising:
 performing an anodization process on the second surface region to form an anodized region, wherein the first cladded region includes a corner of the metal enclosure, and wherein the anodized region extends to meet the first cladded region at the corner; and 
 performing a finishing process on at least one of the anodized region and the first cladded region, wherein the finishing process includes a removal process which makes the anodized region and the first cladded region substantially flush with each other where these regions meet at the corner. 
 
     
     
       8. The method of  claim 1 , wherein the first cladded region is adjacent the second cladded region. 
     
     
       9. The method of  claim 1 , wherein the second cladding material has a composition that is different from a composition of the first cladding material. 
     
     
       10. The method of  claim 1 , wherein performing the first and second laser cladding processes comprises:
 placing the first and second cladding materials into a mold to form a cladding preform; 
 placing the metal enclosure into the mold, wherein, in the mold, the first and second cladding materials of the cladding preform are adhered to the respective first and second external surface regions of the metal enclosure; 
 removing from the mold the metal enclosure with the cladding preform adhered to the metal enclosure; and 
 applying a laser beam to the cladding preform to form the first and second cladded regions, wherein action of the laser beam causes a metallurgical bond to form between the first and second cladding materials and the respective first and second external surface regions of the metal enclosure. 
 
     
     
       11. The method of  claim 10 , wherein the metal enclosure is placed into the mold prior to the first and second cladding materials being placed into the mold. 
     
     
       12. The method of  claim 1 , wherein a hardness of the first cladded region is greater than a hardness of the second cladded region, and wherein a fracture toughness of the second cladded region is greater than a fracture toughness of the first cladded region. 
     
     
       13. The method of  claim 1 , wherein the first and second external surface regions form at least a portion of a same surface of the metal enclosure. 
     
     
       14. The method of  claim 1 , wherein the metal enclosure includes two surfaces, the first external surface region forming at least a portion of one of the two surfaces, and the second external surface region forming at least a portion of the other of the two surfaces. 
     
     
       15. A method comprising:
 providing a metal enclosure forming at least a portion of an electronic device housing, the metal enclosure including a first surface region and a second surface region; 
 performing a laser cladding process on the first surface region to create a first cladding layer; and 
 performing a laser cladding process on the second surface region to create a second cladding layer, 
 wherein the first cladding layer and the second cladding layer have different properties. 
 
     
     
       16. The method of  claim 15 , further comprising performing a finishing process on the first and second cladding layers. 
     
     
       17. The method of  claim 15 , wherein the different properties of the first and second cladding layers include a difference in a structural property or a thickness of the first and second cladding layers, wherein the structural property is chosen from corrosion resistance, hardness, and fracture toughness. 
     
     
       18. The method of  claim 15 , wherein the different properties of the first and second cladding layers include a difference in colors of the first and second cladding layers. 
     
     
       19. The method of  claim 15 , wherein the first cladding layer is formed from a first cladding material, and the second cladding layer is formed from a second cladding material, wherein the different properties of the first and second cladding layers include a difference in compositions of the first and second cladding materials. 
     
     
       20. The method of  claim 19 , wherein the compositions of the first and second cladding materials each comprise a ceramic and a metal, wherein the difference in compositions of the first and second cladding materials include a volume percent of the ceramic in the first cladding material being greater than a volume percent of the ceramic in the second cladding material.

Description:
BACKGROUND 
     1. Field 
     The present invention relates to treatments for a surface of a metal article and an article with a treated surface. More particularly, the present invention relates to performing laser cladding treatments to coat all or part of one or more surfaces of a metal enclosure with cladding material, and further relates to a metal enclosure with different coatings of cladding material on selective regions to provide different structural and/or cosmetic properties at these regions of the metal enclosure. 
     2. Background Art 
     Many products in the commercial and consumer industries are metal articles, or include metal enclosures. The metal surfaces of these products may be treated by any number of processes to alter the surface to create a desired effect, either functional (such as corrosion resistance and wear resistance), cosmetic (such as color, shininess or surface texture), or both. Such characteristics are important to consumers because they want to purchase products that have surfaces that will stand up to normal wear and tear of everyday use and continue to look brand new. One example of such a surface treatment is anodization. Anodizing a metal surface converts a portion of the metal surface into a metal oxide, thereby creating a metal oxide layer. The porous nature of the metal oxide layer created by anodization can be used for absorbing dyes to impart a color to the anodized metal surface. While anodized metal surfaces can provide increased corrosion resistance and wear resistance, it can be difficult for a metal oxide layer to form at edges, such as at corners of the metal article. The metal oxide grows vertically into and outward from a surface, and these growing surfaces intersect at a corner such that the corner itself does not have metal oxide growth. 
     BRIEF SUMMARY 
     In broad terms, a metal enclosure can be surface treated using a laser cladding process to create a cladding layer on a surface region of the enclosure. The cladding layer can have one or more structural properties chosen from corrosion resistance, hardness, and fracture toughness that are greater than corresponding structural properties of the underlying metal substrate. The cladding layer can have a cosmetic property such as color, shininess and/or texture, that is different from a corresponding cosmetic property of the underlying metal substrate. The metal enclosure can form all or part of an electronic device housing. 
     The metal enclosure can include a second surface region having a cladding layer. The cladding layers on the first and second surface regions can have different properties. For example, the cladding layers can have different structural properties, such as different corrosion resistance, hardness, and/or fracture toughness. The cladding layers can have different thicknesses. The cladding layers can have different appearances, such as different colors, shininess and/or texture. The cladding layers on the first and second surface regions can have different compositions, which can achieve the difference in structural properties or appearance between the cladding layers. The metal enclosure can be surface treated to create an anodized layer on one surface region and a cladding layer on another surface region using respective anodization and laser cladding processes. The metal enclosure can have non-anodized corners adjacent the anodized layer, and the corners can be coated with the cladding layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES 
       The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate the present invention by way of example, and not by way of limitation. The drawings together with the description, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention. 
         FIG. 1  is a flowchart of an exemplary method for surface treating a metal enclosure to obtain a surface region that is laser clad, in accordance with one embodiment of the present application. 
         FIGS. 2-4  are enlarged cross-sectional side views of a metal enclosure at different stages in the method of  FIG. 1 , in accordance with one embodiment of the present application. 
         FIG. 5  is a flowchart of exemplary substeps for performing the laser cladding step of the method of  FIG. 1 , in accordance with one embodiment of the present application. 
         FIGS. 6-8  are enlarged cross-sectional side views of a metal enclosure at different stages in performing the laser cladding substeps of  FIG. 5 , in accordance with one embodiment of the present application. 
         FIG. 9  is a flowchart of exemplary substeps for performing the laser cladding step of the method of  FIG. 1 , in accordance with one embodiment of the present invention. 
         FIG. 10  a flowchart of an exemplary method for surface treating a metal enclosure to obtain a surface region that is anodized and another surface region that is laser clad, in accordance with one embodiment of the present application. 
         FIGS. 11-14  are enlarged cross-sectional side views of a metal enclosure at different stages in the method of  FIG. 10 , in accordance with one embodiment of the present application. 
         FIG. 15  is a perspective view of an exemplary electronic device having a metal enclosure made according to an embodiment of a method of the present application. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention will be described with reference to the accompanying drawings, in which like reference numerals refer to similar elements. While specific configurations and arrangements are discussed, it should be understood that this is done for illustrative purposes only. A person skilled in the pertinent art will recognize that other configurations and arrangements can be used without departing from the spirit and scope of the present invention. It will be apparent to a person skilled in the pertinent art that this invention can also be employed in a variety of other applications. 
     In embodiments presented herein, a metal enclosure is surface treated using a laser cladding process to create a cladding layer on a surface region of the enclosure. The cladding layer can be more durable or cosmetically appealing than the underlying metal substrate and provide the enclosure with a more durable and/or attractive surface. For example, in some embodiments, the cladding layer can have a structural property chosen from corrosion resistance, hardness, and fracture toughness that is greater than a corresponding structural property of the underlying metal substrate. The cladding layer car have a cosmetic property such as color, shininess and/or texture, that is different from that of the underlying metal substrate. 
     As known to one of skill in the art, a laser cladding process is a hard coating technique in which a cladding material with the desired properties is fused onto a metal substrate by means of a laser beam, resulting in a metallurgical bond between the cladding material and the metal substrate. Laser cladding can yield a cladding layer formed of the cladding material that can have superior properties in terms of pureness, homogeneity, hardness, bonding and microstructure, as compared to other hard coating techniques. The laser beam can be controlled to provide focused heating and localized melting of the substrate and the cladding material. Compared to conventional welding, laser cladding can provide minimal dilution and a small heat affected zone where the substrate and the cladding material melt and minimally mix together to achieve the metallurgical bond. A high degree of mixing between the cladding material and the substrate, which can deteriorate the properties of the resulting cladding layer, can be avoided using a laser cladding process. In some embodiments presented herein, a laser cladding process is used to clad a surface region of a metal enclosure. In some embodiments, laser cladding can be used to form the metal enclosure itself, in which the enclosure is manufactured as a near-net-shape part using a laser cladding process. 
     A laser cladding process can be automated and can be controlled to precisely coat a selective surface region of the metal enclosure with a cladding layer. The thickness of the cladding layer can be selected depending on the target structural properties and/or cosmetic properties (e.g., color, shininess and/or texture). The laser cladding process can control the deposition of the cladding layer to achieve a desired thickness varying between several micrometers to several centimeters. For example, in some embodiments, a laser cladding process is used to apply a cladding layer having a thickness in a range of from about 50 μm to about 2 mm, or a thickness of from about 0.1 mm to about 0.5 mm in other embodiments. Exemplary deposition rates can involve several square-cm per minute for cladding layers with a thickness of around 1 mm. 
     A wide selection of homologous and non-homologous powder materials can be used as the cladding material, and the materials can be selected depending on the target structural properties and/or cosmetic properties. In some embodiments, the cladding material can include a ceramic and a metal. For example, the cladding material can include ceramic particles (e.g., titanium carbide, tungsten carbide) suspended in a metal matrix (e.g., stainless steel and other steel alloys, as well as aluminum, nickel, cobalt, magnesium, titanium and alloys thereof). In some embodiments, the matrix metal is selected to be the same metal which forms the metal substrate. The homogeneity of the cladding metal matrix and the metal substrate can improve the metallurgical bond. The ratio of ceramic to metal can be selected depending on the target structural properties and/or cosmetic properties. For example, increasing the loading of the ceramic particles in a metal matrix can achieve a harder, more brittle cladding layer. Decreasing the loading of the ceramic particles in the metal matrix can achieve a cladding layer that is less brittle (i.e., lower fracture toughness) and has a lower hardness. A harder cladding layer can be more resistant to abrasions, scratches and other wear, and a less brittle cladding layer can be more resistant to fracturing when subject to impact forces during use of the metal enclosure. In some embodiments, the material of cladding layer includes hard, brittle particles (e.g., carbides) in a ductile metal matrix that improves the cladding material&#39;s resistance to fracture. The ratio of ceramic particles to matrix material can be selected to achieve a desired balance of both hardness and fracture toughness properties. 
     In some embodiments, the volume percent of ceramic particles in the cladding material does not exceed about 60 vol %, does not exceed about 50 vol %, or is from about 40 vol % to about 50 vol %. In some embodiments, the powder materials of the cladding material can be mixed with a binder to form agglomerated powder or to form a paste, to facilitate application of the cladding material to the metal substrate during the laser cladding process. 
     The cladding materials can be selected depending on the target cosmetic properties. For example, the color of the cladding layer can also be modified by changing the composition of the metal matrix and/or the ratio of ceramic particles to metal matrix. For example, in some embodiments, the different colors achieved by varying the cladding material composition appear as different shades of grey. In some embodiments, a glass matrix is used in the cladding material, which can render the cladding layer translucent or transparent and the color of the underlying metal substrate can show through the cladding layer. The cosmetic properties of the cladding layer can also be varied by adjusting the size and/or shape of the particles in the matrix, which can affect the texture. 
     The metal substrate of the metal enclosure can be any suitable metal for forming metal enclosures (e.g., stainless steel and other steel alloys, as well as aluminum, nickel, cobalt, magnesium, titanium and alloys thereof). The metal enclosure can be formed using any metalworking process (e.g., extrusion, cast, forging, machining, metal injection molding (MIMS) processes). 
     As an example, a method to achieve a laser clad metal enclosure according to some embodiments presented herein, a metal enclosure can be forged, with any additional structural details thereafter machined (such as machining to provide grooves or holes or to refine the profile of the enclosure using, e.g., computer numerical controls (CNC)). Then, all or part of one or more surfaces of the metal enclosure can be laser clad with a cladding material. For example, in some embodiments, all or part of the exterior surface of the metal enclosure is laser clad. In some embodiments, the entire exterior surface of a metal enclosure is laser clad. Following the laser cladding process, any additional structural details can be machined into the laser clad surface. In some embodiments, the metal enclosure forms all or part of an electronic device housing. The laser clad surface can be provided on the exterior surface of the metal enclosure to constitute an outer, exposed surface of the device. 
     The metal enclosure can be provided with an initial base surface finish prior to performing the laser cladding process, and a finish can be provided on the cladding layer after performing the laser cladding process. For example, a finishing process such as blasting can be performed on the surface region of the metal substrate prior to being laser clad, and a finishing process such as polishing can be performed on the resulting cladding layer. Any mechanical or chemical finishing processes known to one of skill in the relevant arts can be performed on the metal substrate or the cladding layer. Non-limiting examples of mechanical finishing processes include polishing (e.g., lapping or buffing), blasting (e.g., grit or sand blasting), and mass finishing methods such as sanding, tumbling, brushing, and any combination thereof. Non-limiting examples of chemical finishing processes include electropolishing and chemical polishing, such as bright dipping. Moreover, finishing of a cladding layer on a surface region can include application of a top coating, such as a powder coating, clear coating, lacquer or other cosmetic finishing layer. In some embodiments, finishing of a cladding layer on a surface region can also include a removal process (e.g., machining) for leveling the cladding layer relative to adjacent surface layers (see, e.g., steps  30  and  50  of the embodiments illustrated in later-described  FIGS. 2-4  and  10 ). 
     A laser cladding process can involve a 1-stage or a 2-stage process, as known to one of skill in the relevant arts. In a 1-stage process, the cladding material is applied during application of the laser beam (e.g., as a powder or wire fed alongside the laser beam). The powder can be injected onto the substrate by either coaxial or lateral nozzles relative to the laser&#39;s position as known in the art. In a 2-stage process, the cladding material is preplaced on the substrate surface (e.g., as preplaced powder, paste/binder mix, plate, wire, through plasma spraying or flame spraying). The cladding material is then melted onto the substrate using a laser beam. In some embodiments, preplacement of cladding material on multiple surfaces of a 3-D enclosure can achieved by using a mold within which the preform is adhered to the metal enclosure (see, e.g., laser cladding steps of later-described  FIG. 9 ). The metal enclosure is then removed with the cladding material being preplaced on the desired surface regions of the enclosure. The laser beam can then be applied to bond the preplaced cladding material to the enclosure at the desired surface regions. 
     As known in the art, the laser beam causes a melt pool to form in the beam&#39;s path. Removal of the beam from the melt pool allows the pool to solidify and produce a track of a solid clad layer following the beam&#39;s path. Thereafter, if desired, another clad layer can be deposited on top of the first clad layer to achieve a desired thickness or property of the final cladding layer. Either the laser beam or the substrate can be kept stationary while the other of the substrate or the laser beam is controlled to move in the x,y,z, directions so that the beam tracks along the surface of the substrate, locally melting the cladding material in the beam&#39;s path to bond the cladding material onto the substrate. In some embodiments, the metal substrate can be preheated before laser cladding, in order to reduce the cooling rates in the cladding layer and minimize or prevent cracking of the layer on cooling. 
     The resulting cladding layer on the metal enclosure can be one or more stacked clad layers. In some embodiments, the cladding layer is one clad layer, and in some embodiments, the clad layer is a plurality of clad layers. In cases where multiple clad layers form a cladding layer, the number of clad layers is optimized to a minimum amount, because the bond between adjacent clad layers can fail and adversely affect the mechanical properties of the cladding layer. 
     The flowcharts and illustrations of  FIGS. 1-15  will now be described to further illustrate exemplary methods and laser clad metal enclosures according to embodiments presented herein. It should be understood that any features of an embodiment disclosed herein can be combined with any features of any other embodiment disclosed herein, without departing from the scope of the present disclosure. Thus, any of the features of the methods and metal enclosures described above can be combined with any features of the methods and metal enclosures described below with reference to  FIGS. 1-15 . 
       FIG. 1  is a high level flowchart of an exemplary method for surface treating a metal enclosure to obtain a surface region that is laser clad. The method includes a step  10  of providing a metal enclosure (which, in some embodiments, can be provided with a base finish as described above), followed by a step  20  and an optional step  30 . In step  20 , a laser cladding is performed on one or more region(s) of the metal enclosure. Optionally, step  20  can be followed by step  30  of performing a finishing process on the cladded region(s). 
     In some embodiments, the laser cladding process is used to deposit inlays of the cladding material. For example, the surface region to be laser clad is a groove in a surface of the metal enclosure. Laser cladding the groove inlays the cladding material in the groove. The resulting cladding layer in the groove can be subjected to a finishing process that removes any excess cladding so that the cladding layer is substantially flush with the adjacent surface of the enclosure.  FIGS. 2-4  are enlarged cross-sectional side views of a metal enclosure at different stages in the method of  FIG. 1 , in which the cladding material is inlaid on the metal enclosure according to one embodiment presented herein. As illustrated in  FIG. 2 , in step  10 , a metal enclosure  15  is provided. Metal enclosure  15  has a surface  16  including an area forming a surface region  16   a . Surface region  16   a  is a groove  14  in surface  16 . In step  20  illustrated in  FIG. 3 , a laser cladding process is performed to coat surface region  16   a  with a cladding layer  25  so as to fill groove  14  with cladding material. A metallurgical bond  70  is formed between cladding layer  25  and the underlying metal of surface region  16   a . Following the cladding process, excess cladding material of layer  25  may extend out of groove  14 , above surface  16  of enclosure  15 . In step  30  illustrated in  FIG. 4 , cladding layer  25  is subjected to a finishing process to remove this excess cladding material. The finished surface of cladding layer  25  is substantially flush with adjacent surface  16  of the enclosure  15 , and cladding layer  25  has a thickness corresponding to the depth of groove  14 .  FIGS. 2-4  are merely exemplary and provided for explanatory purposes of the methods described herein, and other variations of treating metal enclosure  15 , to include a cladded region formed by cladding layer  25  are described in the embodiments that follow and should be apparent to one of skill in the art. 
     In some embodiments, metal enclosure can include one or more additional surface regions coated with one or more cladding layers that each have different properties. For example, in some embodiments, the metal enclosure can include a second surface region having a second cladding layer. The cladding layers on the first and second surface regions can have different properties (e.g., different structure and/or cosmetic properties). In some embodiments, the cladding layers on the first and second surface regions can have different compositions, which can achieve the difference in structural properties or appearance between the cladding layers. For example, the compositions of the cladding layers can include a ceramic and a metal, and the ratio of ceramic to metal can vary between cladding layers at different surface regions. In some embodiments, the cladding layers on the first and second surface regions can have different thicknesses. A surface region that may be exposed to a higher likelihood of receiving impact during user-handling of the metal enclosure may have a cladding layer with a greater fracture resistance as compared with a cladding layer on another surface region without the same likelihood of impact exposure. A surface region that may be exposed to a higher likelihood of receiving scratches or abrasions during use of the metal enclosure may have a cladding layer which provides a greater hardness as compared with a cladding layer on another surface region without the same likelihood of such exposure. 
       FIG. 5  is a high-level flowchart of exemplary substeps  21  and  23  of step  20  for performing the laser cladding process to achieve different surface regions clad with cladding layers having different properties. In step  21 , a first surface region of the metal enclosure is laser clad with a first cladding layer, and in step  23 , a second surface region of the metal enclosure is laser clad with a second cladding layer.  FIGS. 6-8  are enlarged cross-sectional side views of metal enclosure  15  illustrating substeps  21  and  23 . In the embodiment of step  10  shown, metal enclosure  15  is provided, in which surface  16  of metal enclosure  15  includes first and second surface regions  16   a  and  16   b . Metal enclosure  15  has a different surface  18  having a surface region  18   a . Surfaces  16  and  18  are immediately adjacent to each other, with surface regions  16   b  and  18   a  meeting at a shared edge, at corner  19 . In step  21  illustrated in  FIG. 7 , first cladding layer  25  is coated on first surface region  16   a  using a laser cladding process. In step  23  illustrated in  FIG. 8 , a second cladding layer  35  is coated on either second surface region  16   b , surface region  18   a , or both of these regions, using a laser cladding process. As illustrated in  FIG. 8 , both surface regions  16   b  and  18   a  are laser clad with a second cladding layer  35 . Metallurgical bond  70  is formed between cladding layers  25  and  35  and the underlying metal of surfaces  16  and  18 . 
     Cladding layers  25  and  35  may have different properties (e.g., structural and/or cosmetic properties such as earlier described). In some embodiments, cladding layers  25  and  35  are formed of the same cladding material (with the same composition) but with different thicknesses, which result in differences in properties between layers  25  and  35 . In some embodiments, cladding layers  25  and  35  are formed of different cladding materials (with different compositions). The cladding layers  25  and  35  (with different compositions) can further differ in thickness. In some embodiments, the cladding material compositions of cladding layers  25  and  35  differ in type and/or amount of components. For cladding materials including particles (e.g., ceramic particles) suspended in a matrix material (e.g., a metal matrix), the type of matrix material or the type of particles may differ between compositions of cladding layers  25  and  35 . The compositions of cladding layers  25  and  35  can further differ in the relative ratio (e.g., volume ratio) of particles to matrix material. 
     In some embodiments, the cladding materials of cladding layers  25  and  35  can each comprise the same ceramic and metal matrix, with the difference in compositions being a difference in a volume percent of ceramic particles in each cladding layer. As an example only and not by way of limitation, a volume percent of the ceramic particles in first cladding layer  25  can be greater than a volume percent of the ceramic particles in second cladding layer  35 , or vice versa. In some embodiments, this difference in properties of cladding layers  25  and  35  can be achieved by varying the composition of the cladding materials forming cladding layers  25  and  35 . For example, the composition of cladding layer  35  can have a lower volume percent of hard ceramic particles (relative to that of cladding layer  25 ) to improve fracture toughness, and the composition of cladding layer  25  can have a higher volume percent of hard ceramic particles to improve hardness. In the embodiment of  FIG. 8 , cladding layer  35  coats corner  19  of metal enclosure  15 . Corner  19  may have a higher likelihood of receiving impact forces during user-handling of metal enclosure  15  than surface region  16   a . For example, a hand-held electronic device can include metal enclosure  15  having cladding layers  25  and  35  on its exterior surfaces (see, e.g., device  100  of later-described  FIG. 15 ). If the device is dropped to the ground, corner  19  can be a likely site of impact with the ground. Surface region  16   a  may have a higher likelihood of receiving scratches or abrasions during use of metal enclosure  15  than surface regions  16   b  and  18   a  at corner  19 . In such instances, it may be desirable for cladding layer  35  to have a greater fracture toughness than that of cladding layer  25 , and for cladding layer  25  to have a greater hardness than that of cladding layer  35 . 
       FIGS. 6-8  are merely exemplary and provided for explanatory purposes of the methods described herein, and other variations of treating metal enclosure  15 , to include two cladded regions formed by respective cladding layers  25  and  35  are described in the embodiments that follow and should be apparent to one of skill in the art. It should also be apparent that the more than two cladding layers can laser clad respective surface regions of metal enclosure  15 . 
     Use of a 1-stage or a 2-stage laser cladding process can be employed for coating metal enclosure  15  with cladding layers  25  and  35 . In some embodiments, cladding layers  25  and  35  are sequentially coated on surface regions that are immediately adjacent to each other (e.g., regions  16  and  16   b  or regions  16   b  and  18   a ) and abut each other. In such embodiments, a suitable masking material can be used to mask one cladding layer (e.g., layer  25 ) on enclosure  15  while the other cladding layer (e.g., layer  35 ) is deposited via the laser cladding process. The masking can be used to provide additional precision to depositing cladding layers  25  and  35  at the boundary where they meet. In some embodiments, the cladding materials can be deposited with the desired precision by virtue of the focus of the laser beam, and masking is unnecessary. 
     In some embodiments employing a 2-stage process, a mold can be used to preplace the cladding materials (e.g., cladding materials of layers  25  and  35 ) on a 3-D substrate (e.g., on surfaces  16  and  18  of metal enclosure  15 ) prior to application of the laser beam.  FIG. 9  is a high-level flowchart of exemplary substeps  22 ,  24 ,  26  and  28  of step  20  for performing a 2-stage laser cladding process using a mold. As an exemplary embodiment, reference will be made to cladding layers  25  and  35  shown in  FIG. 8  when describing the substeps of  FIG. 9 . In step  22 , the cladding materials are placed in a mold to form a cladding preform, and in step  24 , metal enclosure  15  is placed into the mold. Placement of the cladding materials in the mold (step  22 ) can occur before or after placement of metal enclosure  15  in the mold (step  24 ). The cladding preform can line the interior of the mold so that surface region  16   a  of enclosure  15  in the mold faces the cladding materials corresponding to cladding layer  25 , and so that surface regions  16   b  and  18   a  of enclosure  15  face the cladding materials corresponding to cladding layers  35 . In the mold, the materials of first and second cladding layers  25  and  35  are adhered to the respective surface regions  16   a ,  16   b , and  18   a . Any suitable mechanism can be used to adhere the preform of cladding materials to the surfaces of metal enclosure  15 . For example, in some embodiments, an adhesive is used to adhere the cladding preform to enclosure  15 . In step  26 , metal enclosure  15  is removed from the mold. Metal enclosure  15  has the cladding preform adhered thereto. In step  28 , a laser beam is applied to the cladding preform to metallurgically bond (see, e.g., metallurgical bond  70 ,  FIG. 8 ) the cladding materials to surface regions  16   a ,  16   b , and  18   a  to create respective cladding layers  25  and  35 . 
     It should be understood that the foregoing reference to coating enclosure  15  with two cladding layers  25  and  35  of  FIG. 8  is merely exemplary and provided for explanatory purposes of the substeps of  FIG. 9 , and other variations should be apparent to one of skill in the art. For example, in some embodiments, the substeps of  FIG. 9  can be employed to laser clad all or part of a 3-D metal enclosure with one cladding layer (e.g., either one of layers  25  or  35 ) or for laser cladding all or part of a 3-D metal enclosure with more than two cladding layers. 
     In some embodiments, the metal enclosure can be surface treated to create an anodized layer on one surface region and a cladding layer on another surface region using respective anodization and laser cladding processes. The metal enclosure can have non-anodized corners adjacent the anodized layer, and the corners can be coated with the cladding layer. Thus, surfaces (such as corners) where it may be difficult for a metal oxide layer to form an anodized layer can instead be laser clad.  FIG. 10  is a high level flowchart of an exemplary method for surface treating a metal enclosure to obtain a surface region that is laser clad and another surface region that is anodized. The method includes a step  10  of providing a metal enclosure (which, in some embodiments, can be provided with a base finish as described above), followed by a cladding step  20  and an anodizing step  40  (in either order), and an optional step  50 . In cladding step  20 , a laser cladding process is performed on a first surface region of the metal enclosure to form a cladded region. In anodizing step  40 , an anodization process is performed on a second surface region of the metal enclosure to form an anodized region. Optionally, cladding step  20  and anodizing step  40  can be followed by step  50  of performing a finishing process on either or both of the cladded region and the anodized region. Any suitable finishing processes known to one of skill the art can be used for cladded region and the anodized region. For the anodized region, finishing processes can include dyeing and/or sealing the anodized region as known in the art. After dyeing and/or sealing, additional finishing steps (e.g., polishing or texturing) may be performed, including any of the mechanical and chemical finishing processes described earlier with reference to finishing the base metal of the enclosure and the cladding layer. 
     As earlier described, the laser cladding process can be any of one or more laser cladding surface treatments as known to one of skill in the art. The anodization process can be any of one or more anodization surface treatments as known to one of skill in the art. Such anodization surface treatments can include standard and hard anodization methods, for example. Standard anodizing and hard anodizing are terms of art. Standard anodizing refers to an anodization process using a sulfuric acid bath that is able to produce an oxide layer of up to about 25 microns (μm). Hard anodizing refers to an anodization process using a sulfuric acid bath maintained at about or slightly above the freezing point of water, for example in a range between about 0 and 5 degrees Celsius, to produce an oxide layer of up to about 100 microns. Standard anodized layers are generally a brighter color than hard anodized layers when dyed with the same solution, and when neither is dyed. Hard anodized layers, as the name connotes, are harder than standard anodized layers and therefore are more scratch and abrasion resistant. In some embodiments, a dual anodization treatment can be used to form anodized layer  25 , whereby anodized layer  25  includes both standard and hard anodized layers and/or regions, such as described in detail in U.S. Pat. No. 8,398,841, which is incorporated herein in its entirety by reference thereto. 
     In some embodiments, cladding step  20  includes the substeps of  FIG. 5 , whereby the cladded region includes regions with different cladding layers which can have different properties. In some embodiments, cladding step  20  includes the substeps of  FIG. 9 , in which a 2-stage cladding process using a mold is employed to laser clad the first surface region. Cladding step  20  can be conducted before or after anodizing step  40 . In some embodiments, a suitable masking material can be used to mask one of the first and second surface regions while operations are performed on the other of the second and first surface regions. For example, cladding step  20  can be conducted prior to anodizing step  40 . The second surface region can be masked while the first surface region is clad. The masking on the second surface region can be removed, and the cladded region can then be masked. Masking can protect the cladded region from undesired effects of the subsequent anodization process. The second surface region can then be anodized, whereafter the masking on the cladded region can be removed. In some embodiments, the cladding materials can be deposited with the desired precision by virtue of the focus the laser beam, and masking of the second surface region is unnecessary. 
     As another example, anodizing step  40  can be conducted prior to cladding step  20 . The first surface region can be masked while the second surface region is anodized. The masking on the first surface region can be removed, and the anodized region can then be masked. The first surface region can then be laser clad, whereafter the masking on the anodized region can be removed. In some embodiments, the cladding materials can be deposited with the desired precision by virtue of the focus of the laser beam, and masking of the anodized region is unnecessary. 
       FIGS. 11-14  are enlarged cross-sectional side views of metal enclosure  15  at different stages in the method of  FIG. 10 , in an embodiment where step  40  is conducted prior to step  20 . In the embodiment illustrated in  FIG. 11 , in step  10 , metal enclosure  15  has surfaces  16  and  18  which are joined by corner  19  which is chamfered and has a surface  12 . In anodizing step  40  illustrated in  FIG. 12 , surfaces  16  and  18  are anodized to form respective anodized layers  45  and  47 . In cladding step  20  illustrated in  FIG. 13 , surface  12  of chamfered corner  19  is laser clad with cladding layer  35 . Anodized layer  45  extends to meet cladding layer  35  at edge  11  of chamfered corner  19 . Anodized layer  47  extends to meet cladding layer  35  at edge  13  of chamfered corner  19 . In step  50  illustrated in  FIG. 14 , a finishing process is conducted on layers  45 ,  47  and/or  35 . For example, anodized layers  45  and/or  47  can be dyed and/or sealed, and can further be provided with a polished or blasted finish. Cladding layer  35  can be provided with a polished or blasted finish, for example. In the embodiment illustrated, after step  20 , anodized layers  45  and  47  extend higher than cladding layer  35  at edges  11  and  13 . In such embodiments, the finishing process for anodized layers  45  and  47  can include removal of excess metal oxide so that anodized layers  45  and  47  are substantially flush with cladding layer  35  where these layers touch at edges  11  and  13 . As result of treating metal enclosure  15  with the laser cladding and anodized processes as described herein, chamfered corner  19 , which may be difficult to anodize, can instead be clad with cladding layer  35 . Moreover, cladding layer  35  can have properties which provide improved structural and/or cosmetic properties compared to the underlying metal substrate. For example, cladding layer  35  can have a higher corrosion resistance than the underlying metal substrate. The composition of cladding layer  35  may be selected to provide improved hardness and/or fracture toughness. For example, cladding layer  35  may be configured to have a fracture toughness sufficient to withstand the expected impact forces and/or abrasions that corner  19  may be exposed to during use of metal enclosure  15 .  FIGS. 11-14  are merely exemplary and provided for explanatory purposes of the methods described herein, and other variations of treating metal enclosure  15 , to include cladded and anodized regions should be apparent to one of skill in the art. 
     Applications of metal enclosures produced according to the methods described herein can include any product having an enclosure made of metal. In some embodiments, the product is an electronic device (e.g., a PC computer, tablet, cell phone, MP3 player, scanner), and metal enclosure  15  forms all or part of the housing of the electronic device.  FIG. 15  illustrates a perspective view of an exemplary MP3 player device  100  according to one embodiment of the present application. Device  100  has a housing  110 , which includes opposite front and rear walls  17  (rear wall hidden from the view illustrated) joined together by metal enclosure  15  extending around the periphery of front and rear walls  17 . Metal enclosure  15  has top and bottom exterior surfaces  16  (top surface hidden from the view illustrated), and left and right side exterior surfaces  18  (left side surface hidden from the view illustrated). Bottom surface  16  of metal enclosure  15  includes adjacent surface regions  16   a  and  16   b  that meet at a point m. Surface region  16   a  is laser clad with cladding layer  25 , and surface region  16   b  is laser clad with cladding layer  35 . Connector ports  112  and  114  (e.g., for receiving audio and power jacks) are formed in surface region  16   a  of bottom surface  16 . Side surface  18  including surface region  18   a  is also laser clad with cladding layer  35 . Thus, cladding layer  35  coats corner  19  of metal enclosure  15 . The other exterior surfaces  16  and  18  (hidden from the view illustrated) can likewise be laser clad with one or more cladding layers at localized surface regions. For example, cladding layer  35  can also be deposited to coat the other three corners at points a, b, c of metal enclosure  15 . Interior surfaces of metal enclosure  15  can also be laser-clad with one or more cladding layers (e.g., cladding layers  25  and/or  35 ). In some embodiments, front and rear walls  17  can be metal, and all or part of the surfaces of walls  17  can be laser clad, anodized, and/or provided with another metal surface treatment. 
     In some embodiments, surface region  16   a  may have a higher likelihood of receiving scratches or abrasions during use of device  100  than surface regions  16   b  and  18   a  (e.g., surface region  16   a  may be scratched by audio and power jacks attaching to connector ports  112  and  114 ). Corner  19  may have a higher likelihood than surface region  16   a  of receiving greater impact forces if a user drops device  100 . In such instances, it may be desirable for cladding layer  35  to have a greater fracture toughness than that of cladding layer  25 , and for cladding layer  25  to have a greater hardness than that of cladding layer  35 . 
     The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, and without departing from the general concept of the present invention. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. 
     It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance. In addition, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Metadata:
Filing Date: 20120326
Publication Date: 20140527
Grant Date: 20140527
Priority Date: 20120326
Inventors: BROWNING LUCY E.
POOLE JOSEPH C.
PREST CHRISTOPHER D.
ZADESKY STEPHEN P.
Assignee: APPLE INC
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Family ID: 49210719