Powder Metallurgy of High Density Helical Gears

Powder Metallurgy is a proven technology to produce high strength gears for the automotive industry. Advances in powder production, compaction, and sintering combined with double pressing have enabled overall part densities up to 7.5 g/cm³ in spur gears. However, helical gears are more difficult to produce to these same densities because the geometry does not lend itself to the DP/DS process. Described in this paper is a P/M parts making technology capable of producing single pressed and sintered helical gears with densities greater than 7.4 g/cm³. Description of a prototype run will be presented with the resulting sintered part densities and part-to-part variability. To further enhance the gear performance and gear tolerance of these helical gears, the gears were subsequently surface densified via rolling. Improvements in the surface density and gear quality will be described.