Gear wheels rolled from powder metal blanks

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 only through the surfaces of the tooth flank regions to establish densification in the range of 90 to 100 per cent of full theoretical density to a depth of at least 380 microns and up to 1,000 microns.

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 with particle size in the range of 2 to 10 microns selected from among carbon, molybdenum, nickel, copper, vanadium, chromium, manganese, ferro chromium, ferro molybdenum and ferro manganese, and the toothed blank is surface hardened by applying densifying pressure only through the surfaces of the tooth root regions or only through the surfaces of the tooth flank regions to establish densification of 90 to 100 per cent of full theoretical density to a depth of at least 380 microns and up to 1,000 microns beneath the surfaces of the respective regions to which such pressure has been applied, the metal density of the hardened regions (a) being substantially 100 per cent 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.