Gear wheels rolled from powder metal blanks and method of manufacture

A gear wheel formed from a pressed and sintered toothed metal powder blank, wherein the metal powder comprises an admixture of iron powder and at least one alloying addition, and the toothed blank is surface hardened by applying densifying pressure primarily to the surfaces of the tooth root and flank regions to establish densification of 90 to 100 percent of full theoretical density to a depth of at least 380 microns and up to 1,000 microns beneath the surfaces of said regions, the metal density of the wheel:

• (a) being substantially 100 percent of full theoretical density at said surfaces, (b) reducing with increasing depth beneath said surfaces in the hardened regions, and (c) reducing at a rate which is lower at said surfaces and increases with increasing depth in the hardened regions.

A method of making a gear wheel comprising:

• forming a pressed and sintered toothed metal powder blank wherein the metal powder comprises an admixture of iron powder and at least one alloying addition;
• and surface hardening the toothed blank by applying densifying pressure to the surfaces of at least the tooth root and flank regions to establish densification in the range of 90 to 100 percent of full theoretical density to a depth of at least 380 microns and up to 1,000 microns.

A method of making a gear wheel comprising:

• forming a pressed and sintered toothed metal powder blank wherein the metal powder comprises an admixture of iron powder and at least one alloying addition;
• and surface hardening the toothed blank by applying densifying pressure primarily to the surfaces of the tooth root and flank regions to establish densification of 90 to 100 percent of full theoretical density to a depth of at least 380 microns and up to 1,000 microns beneath the surfaces of said regions, wherein the surfaces of said regions of the wheel are densified to substantially 100 percent of full theoretical density, the metal density is reduced with increasing depth from said surfaces of the hardened regions and the rate of such reduction relative to depth is made to be lower at said surfaces and to increase with increasing depth in the hardened regions.

A method of manufacturing a gear wheel by advancing a gear rolling die to rotatably mesh with said gear wheel, said gear rolling die having an axis of rotation substantially parallel to the axis of rotation of said gear wheel, comprising progressively applying said gear rolling die radially against the tooth root and flank regions of a pressed and sintered powder metal blank to establish densification in the range of 90 to 100 percent of full theoretical density to a depth of at least 380 and up to 1,000 microns in said regions.