Post-delubrication peening for forged powder metal components

Abstract

A process of forming powder metal components which minimizes decarburization and oxidation of the component prior to final forging. The process begins by molding powder metal material into a preform configuration. The preform is delubricated to extract lubricant found in the pores of the preform. Passing the preform through a shot peening operation closes a majority of the surface pores creating a densified layer within which interconnected pores are eliminated. Following post-delubrication peening (PDP), the component is sintered and then forged into its final configuration.

Description

[0001] This application claims priority from U.S. Provisional Application No. 60 / 219,516 filed on Jul. 20, 2000, and is a continuation of U.S. patent application Ser. No. 09 / 653,889, filed Sep. 1, 2000.[0002] I. Field of the Invention[0003] This invention relates to shot peening a powder metal component and, in particular, to shot peening the powder metal forged component following delubrication but prior to sintering the powder metal component.[0004] II. Description of the Prior Art[0005] In the currently utilized method of forming powder metal components, the powder metal is molded to a desired configuration then sintered to retain the configuration of the component and finally forged to its final configuration. However, it has been determined that decarburization and oxide penetration occurs between sintering and forging. After exiting from the sintering furnace, the hot part is exposed to the air and the moisture created by lubricant / coolant spraying prior to forging, the part h...

AI Technical Summary

Benefits of technology

[0006] The present invention overcomes the disadvantages of the prior known processes for manufacturing powder metal components by shot peening the preform after delubing and prior to sintering to create a densified outer layer to reduce decarburization, oxide penetration and surface porosity on the finished components.

[0007] The process of the present invention begins by molding powder metal material into a preform configuration. The preform is passed through a delubrication furnace to extract or decompose lubricant found in the preform. This delubrication creates an interconnected porosity. Passing the preform through a shot peening operation closes a majority of the surface pores creating a densified layer with increased ductility and enhanced resistance to cracking. Following post-delubrication shot peening (hereinafter "PDP"), the component is sintered and then forged into its final configuration. The post-delubrication shot peening eliminates oxide in pores and between particles allowing the forging to be more effective in closing pores and establishing inter-particle bonding.

Problems solved by technology

However, it has been determined that decarburization and oxide penetration occurs between sintering and forging.

Oxygen and moisture penetrates the surface through these interconnected pores leading to decarburization and oxide penetration.

Once the surface and pores are oxidized between sintering and forging, it is difficult to close the pores by forging resulting in a weakened component.

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