US20170266726A1

US20170266726A1 - Method and system for surface densification

Info

Publication number: US20170266726A1
Application number: US15/450,691
Authority: US
Inventors: John M. Kremer; Wenying Yang
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2016-03-17
Filing date: 2017-03-06
Publication date: 2017-09-21
Also published as: CN107199341A; CN107199341B

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

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

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.
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.
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

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.
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.
In yet another aspect of the present disclosure the predetermined temperature is maintained using a temperature control feedback system.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

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;

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;

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;

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;

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;

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;

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;

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

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

The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
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.
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.
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.
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.
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.
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.
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.
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.
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.

Claims

What is claimed is:

1. A method for densifying a surface of a powder metal part, the method comprising:

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;

sintering the compacted powder metal blend in an oven;

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.

2. The method of claim 1 wherein 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.

3. The method of claim 2 wherein the predetermined temperature is maintained using a temperature control feedback system.

4. The method of claim 3 wherein the temperature control feedback system uses closed loop temperature control with infrared monitoring or the like for heating the portion of the surface of the powder metal part to a temperature between 300° C. and 700° C.

5. The method of claim 1 wherein 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.

6. The method of claim 1 wherein heating a portion of the surface of the powder metal part includes heating a linear portion of the powder metal part.

7. The method of claim 6 wherein 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.

8. The method of claim 1 wherein the powder metal part comprises 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.

9. The method of claim 1 wherein heating the portion of the surface of the powder metal part includes applying an induction heat with an induction heating device.

10. The method of claim 1 wherein heating the portion of the surface of the powder metal part includes applying microwave radiation with a microwave device.

11. The method of claim 1 wherein 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.

12. A method for densifying a surface of a powder metal part, the method comprising:

blending a plurality of powdered metals to form a powder metal blend;

forming the powdered metal blend into the powder metal part;

sintering the compacted powder metal blend in an oven;

heating a portion of the surface of the powder metal part; and

densifying the portion of the surface of the powder metal part, wherein 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.

13. The method of claim 12 wherein 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.

14. The method of claim 13 wherein 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.

15. The method of claim 12 wherein 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.

16. The method of claim 12 wherein 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.

17. The method of claim 16 wherein heating the portion of the surface of the powder metal part includes applying an induction heat with an induction heating device.

18. The method of claim 16 wherein heating the portion of the surface of the powder metal part includes applying microwave radiation with a microwave device.

19. The method of claim 16 wherein 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.

20. A system for densifying a surface of a powder metal part comprising:

a workstation, wherein the powder metal part is disposed in or on the workstation;

a heating element 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 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; and

a controller configured to control the heating element, the workstation, and the tool, wherein the controller is configured to control a 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.