Abstract:
A method for densifying a surface of a powder metal part, includes blending a plurality of powdered metals to form a powder metal blend, actuating an upper punch and a lower punch to apply pressure to the powder metal blend to compact the powder metal blend, sintering the compacted powder metal blend in an oven, forming the compacted powdered metal blend into the powder metal part, heating a portion of the surface of the powder metal part, and densifying the portion of the surface of the powder metal part for a predetermined period of time after the portion of the powder metal part is heated to a predetermined temperature.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional application No. 62/309,658 filed on Mar. 17, 2016, the entire contents of which are incorporated herein by reference. 
     
    
     INTRODUCTION 
       [0002]    The invention relates generally to a method and system for densification of a surface of a workpiece and more particularly to a method and system for applying heat to a powder metal workpiece before surface densification of the workpiece. 
         [0003]    Forming metal parts from a powder metal blend is a well known technology. A system for forming a powder metal part usually includes a die that is filled with a powder metal blend. Typical dies include an upper punch and a lower punch. The powder metal blend is compacted by actuating the upper punch and the lower punch to apply pressure to the powder metal blend within a die housing. Finally, the powder metal blend is typically sintered in an oven or the like to produce a formed powder metal part. The basic steps in the powder metal forming and surface densification process include blending the desired metal powders and filling the die; compacting the powder metal blend into the desired shape, sintering the compacted part, machining the sintered compacted part into the desired final shape; densifying the surface; heat treating the surface, and finishing the final shape by grinding or the like. 
         [0004]    While current methods and systems for forming powder metal components and for surface densification achieve their intended purpose, the need for new and improved methods and systems for forming and surface densification which exhibit higher mechanical properties are needed. Accordingly, there is a need for an improved, system and method for surface densification of powder metal parts that provides deeper densification into the surface, less damage to existing bonds, and achieves higher levels of surface density. 
       SUMMARY 
       [0005]    According to several aspects a method for densifying a surface of a powder metal part includes blending a plurality of powdered metals to form a powder metal blend, forming the powdered metal blend into the powder metal part, actuating an upper punch and a lower punch to apply pressure to the powder metal blend to compact the powder metal blend, and sintering the compacted powder metal blend in an oven. The method further includes heating a portion of the surface of the powder metal part, and densifying the portion of the surface of the powder metal part for a predetermined period of time after the portion of the powder metal part is heated to a predetermined temperature. 
         [0006]    In another aspect of the present disclosure heating the portion of the surface of the powder metal part includes heating the portion of the surface of the powder metal part to a temperature between 300° C. and 700° C. 
         [0007]    In yet another aspect of the present disclosure the predetermined temperature is maintained using a temperature control feedback system. 
         [0008]    In still another aspect of the present disclosure the temperature control feedback system uses closed loop temperature control with infrared monitoring or the like for heating the powder metal part to a temperature between 300° C. and 700° C. 
         [0009]    In still another aspect of the present disclosure densifying a surface of the powder metal part includes applying a point load on the portion of the surface of the powder metal part using a conical shaped tool. 
         [0010]    In still another aspect of the present disclosure heating a portion of the surface of the powder metal part includes heating a linear portion of the power metal part. 
         [0011]    In still another aspect of the present disclosure densifying the portion of the surface of the powder metal part includes applying a line load on the heated linear portion using at least one roller. 
         [0012]    In still another aspect of the present disclosure the powder metal part includes a gear having gear teeth and densifying the portion of the surface for the powder metal part includes applying a gear meshing load to the gear teeth. 
         [0013]    In still another aspect of the present disclosure heating the portion of the surface of the powder metal part includes applying an induction heat with an induction heating device. 
         [0014]    In still another aspect of the present disclosure heating the portion of the surface of the powder metal part includes applying microwave radiation with a microwave device. 
         [0015]    In still another aspect of the present disclosure heating the portion of the surface of the powder metal part includes applying a laser to the portion of the surface of the powder metal part. 
         [0016]    In still another aspect of the present disclosure a method for densifying a surface of a powder metal part includes blending a plurality of powdered metals to form a powder metal blend, forming the powdered metal blend into the powder metal part, actuating an upper punch and a lower punch to apply pressure to the powder metal blend to compact the powder metal blend, and sintering the compacted powder metal blend in an oven. The method further includes, heating a portion of the surface of the powder metal part, and densifying the portion of the surface of the powder metal part. The densifying the portion of the surface of the powder metal part includes applying a point load on the portion of the surface of the powder metal part using a conical shaped tool for a predetermined period of time after the portion of the powder metal part is heated to a predetermined temperature. 
         [0017]    In still another aspect of the present disclosure applying a point load on the portion of the surface of the powder metal part includes moving the conical shaped tool axially along the powder metal part. 
         [0018]    In still another aspect of the present disclosure applying a point load on the portion of the surface of the powder metal part includes rotating the conical shaped tool about an axis of rotation. 
         [0019]    In still another aspect of the present disclosure applying a point load on the portion of the surface of the powder metal part includes rotating the powder metal part about an axis of rotation. 
         [0020]    In still another aspect of the present disclosure the heating the portion of the surface of the powder metal part includes heating the portion of the surface of the powder metal part to a temperature between 300° C. and 700° C. 
         [0021]    In still another aspect of the present disclosure heating the portion of the surface of the powder metal part includes applying an induction heat with an induction heating device. 
         [0022]    In still another aspect of the present disclosure heating the portion of the surface of the powder metal part includes applying microwave radiation with a microwave device. 
         [0023]    In still another aspect of the present disclosure heating the portion of the surface of the powder metal part includes applying a laser to the portion of the surface of the powder metal part. 
         [0024]    In still another aspect of the present disclosure a system for densifying a surface of a powder metal part includes a workstation. The powder metal part is disposed in or on the workstation. A heating element is adjacent the powder metal part and configured to heat a portion of the surface of the powder metal part to between 300° C. and 700° C. A tool is adjacent the part and configured to apply a point load to a portion of the surface of the powder metal part after the portion of the surface of the powder metal part has been heated. A controller is configured to control the heating element, the workstation, and the tool. The controller is configured to control the rate at which the heating element heats the portion of the surface of the powder metal part, and a rate of movement of the tool relative to the surface of the powder metal part. 
         [0025]    Further features, aspects and advantages of the present invention will become apparent by reference to the following description and appended drawings wherein like reference numbers refer to the same component, element or feature. 
     
    
     
       DRAWINGS 
         [0026]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0027]      FIG. 1A  is a perspective view of a system for densifying a surface of a powder metal part using a conical shaped tool to point load the surface of the powder metal part after the portion of the surface that the point load is applied is heated to a predefined temperature for a predefined duration of time, according to the principles of the present disclosure; 
           [0028]      FIG. 1B  is a front view of a system for densifying a surface of a powder metal part using a conical shaped tool to point load the surface of the powder metal part after the portion of the surface that the point load is applied is heated to a predefined temperature for a predefined duration of time, according to the principles of the present disclosure; 
           [0029]      FIG. 1C  is a side view of a system for densifying a surface of a powder metal part using a conical shaped tool to point load the surface of the powder metal part after the portion of the surface that the point load is applied is heated to a predefined temperature for a predefined duration of time, according to the principles of the present disclosure; 
           [0030]      FIG. 2A  is a perspective view a system for densifying a surface of a powder metal part using a set of rollers for applying a line load to the surface of the powder metal part after the portion of the surface that the line load is applied is heated to a predefined temperature for a predefined duration of time, according to the principles of the present disclosure; 
           [0031]      FIG. 2B  is an end view a system for densifying a surface of a powder metal part using a set of rollers for applying a line load to the surface of the powder metal part after the portion of the surface that the line load is applied is heated to a predefined temperature for a predefined duration of time according to the principles of the present disclosure; 
           [0032]      FIG. 3  is a schematic illustration a system for densifying a surface of a powder metal gear using a gear for applying a meshing load to the surface of the powder metal gear after the portion of the surface that the meshing load is applied is heated to a predefined temperature for a predefined duration of time, according to the principles of the present disclosure; 
           [0033]      FIG. 4  is a schematic illustration a system for densifying a surface of a powder metal part using a coining die for applying a surface load to the surface of the powder metal part after the portion of the surface that the load is applied is heated to a predefined temperature for a predefined duration of time, according to the principles of the present disclosure; 
           [0034]      FIG. 5  is a flow chart illustrating a method for forging a powder metal part and for densifying the surface of the forged powder metal part, according to the principles of the present disclosure; and 
           [0035]      FIG. 6  is a flow chart illustrating an alternative method for forging a powder metal part and for densifying the surface of the forged powder metal part, according to the principles of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0036]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0037]    Referring now to  FIGS. 1A-1C , a system  100  for densification of a surface  102  of a sintered powder metal part  104  and a surface  106  of a powder metal part  108  is illustrated, in accordance with the present invention. The system  100  includes a densification tool  110  and a heating device  112 . Densification tool  110  is conical in shape and has an annular rim  114 . In  FIG. 1A , the annular rim  114  of tool  110  is pressed against surface  102  of the sintered powder metal part  104  and contacts the surface  102 . The powder metal part  104  is disposed in or on a mount or workstation (not shown). As the workstation rotates the powder metal part  104  about its axis, the annular rim  114  of the tool  110  traverses the surface  102  of the powder metal part  104 , applies a point load to densify the surface  102 . In one aspect, a point load is a load applied to substantially a single point of contact between the annular rim  114  of the tool  110  and the surface  102  of the powder metal part  104 . In other words, as the annular rim  114  of the tool  110  applies a point load to the surface  102 , the porosity at the surface  102  is reduced. In one aspect of the present disclosure, the tool  110  moves axially relative to the powder metal part  104  and is thereby applied to the surface  102  over a predetermined portion of an axial extent of the powder metal part  104 . 
         [0038]    In  FIGS. 1B and 1C , the annular rim  114  of the tool  110  is pressed against the surface  106  of the powder metal part  108  and contacts the surface  106 . The powder metal part  108  is disposed in or on a mount or workstation (not shown). As the workstation rotates the powder metal part  108  about its axis, the annular rim  114  of the tool  110  traverses the surface  106  of the powder metal part  108  and the surface  106  is densified. In other words, the porosity at the surface  106  is reduced as the annular rim  114  traverses the surface  106 . In one aspect of the present disclosure, the tool  110  moves radially relative to the powder metal part  108 , as the powder metal part  108  is rotated and is thereby applied to the surface  106  over a predetermined portion of an radial extent of the powder metal part  106 . 
         [0039]    In each of  FIGS. 1A-1C , the heating device  112  is positioned in front of the densification tool  110  relative to the direction of rotation of the powder metal parts  104 ,  108 . As the powder metal parts  104 ,  108  are rotated, the heating device  112  heats up the surfaces  102 ,  106  before the densification tool  110  reaches the heated surfaces  102 ,  106 . Heating device  112 , in one aspect of the present disclosure, is an induction coil, microwave, laser, electron beam or the like. Heating device  112  is configured to heat the surface of a powder metal part to between 300 to 700 degrees Celsius. Additionally, in another aspect of the present disclosure, system  100  includes a feedback temperature controller (not shown) that is configured to control the surface temperature of the powder metal part to between 300 to 700 degrees Celsius. 
         [0040]    Referring now to  FIGS. 2A-2B , an alternate system  200  for densifying a surface  202  of a sintered powder metal part  204  is illustrated in perspective and end views, in accordance with the present disclosure. System  200  includes a plurality of rollers or densification tools  206 , three in the instant embodiment, and a plurality of heating devices  208 , also three in the instant embodiment. The plurality of rollers  206  are positioned at equal distances around the periphery of the powder metal part  204 . However, the present disclosure contemplates that the plurality of rollers  206  are positioned around the periphery of the powder metal part  204  at distances that are not equal. Each of the plurality of rollers  206 , contacts and applies a line load to the surface  202  along a line on the surface of the powder metal part  204  thereby acting to densify the surface  202 . In one aspect, the line load is a pressure applied by the rollers  206  along a length of the rollers  206  in contact with the surface  202  of the powder metal part  204 . The plurality of heating devices  208  are, also, positioned at equal distances around the periphery of the powder metal part  204 . However, the present disclosure contemplates that the plurality of heating devices  208  are positioned around the periphery of the powder metal part  204  at distances that are not equal. As the powder metal part  204  is rotated, the plurality of heating devices  208  heat up the surface  202  before the plurality of densification tools  206  reach the heated surface  202 . 
         [0041]    Referring now to  FIG. 3 , an alternate system  300  for densifying a surface  302  of a sintered powder metal gear  304  is illustrated in a side view, in accordance with the present disclosure. System  300  includes a gear densification tool  306  and a heating device  308 . Gear densification tool  306  is in the shape of a gear having gear teeth  310  that are configured to mesh with gear teeth  312  of gear  304 . Gear densification tool  306  contacts and applies pressure to the surface  302  at the area  314  of meshing contact of the densification tool  306  with the powder metal part  304  and acts to densify the surface  302 . The heating device  308  is positioned at distance from area  314  of meshing contact of the densification tool  306  with the powder metal part  304  on the periphery of the powder metal part  304 . As the powder metal part  304  is rotated, the heating device  308  heats up the surface  302  before the densification tool  306  reaches the heated surface. While  FIG. 3  includes only a single gear densification tool  306  and heating device  308 , it should be understood that additional gear powder metal gears  304 , gear densification tools  306  and heating devices  308  may be used without departing from the scope or intent of the present disclosure. 
         [0042]    Referring now to  FIG. 4 , an alternate system  400  for densifying a surface  402  of a powder metal part  404  is illustrated in a side view, in accordance with the present disclosure. System  400  includes a densification tool  406  and a heating furnace  408 . Densification tool  406  includes an upper punch  410  and a lower punch  412 . Densification tool  406  contacts and applies pressure to the surface  402  of the powder metal part  404  and acts to densify the surface  402  through a coining operation. The heating furnace  408  elevates the temperature of surface  402  of the powder metal part  404  to a temperature of 300 to 700 degrees Celsius. Surface densification is increased by heating the sintered powder metal part  404  just before surface densification is performed. 
         [0043]    Referring now to  FIG. 5 , a method  500  for forming a powder metal part and densifying a surface of the powder metal part is illustrated in flowchart form. The method starts with step  502 , at step  502  the die is filled with a powder metal blend. At step  504  the powder metal blend is compacted. At step  506 , the compacted powder metal blend is sintered. At step  508  the sintered powder metal part is machined to a final shape. At step  510  the machined powder metal part is heated and the surface of the machined powder metal part is densified. At step  512 , the surface of the powder metal part is heat treated. At step  514 , the surface of the heat treated powder metal part is ground as necessary to produce a final product. 
         [0044]    Referring now to  FIG. 6 , a method  600  for forming a powder metal part and densifying a surface of the powder metal part is illustrated in flowchart form. The method starts with step  602 , at step  602  the die is filled with a powder metal blend. At step  604  the powder metal blend is compacted. At step  606 , the compacted powder metal blend is sintered. At step  608  the sintered powder metal part is machined to a final shape. At step  610  the surface of the machined powder metal part is heated to a predefined temperature range. At step  612 , the heated surface of the machined powder metal part is subjected to a densification tool that densifies the heated surface. At step  614 , the surface of the powder metal part is heat treated. At step  616 , the surface of the heat treated powder metal part is ground as necessary to produce a final product. 
         [0045]    The description of the invention is merely exemplary in nature and variations that do not depart from the essence of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.