Powder metal (P/M) process is making inroads in automotive transmission applications because of
substantially lower cost of P/M steel components for high volume production as compared to wrought or
forged steel parts. Although P/M gears are increasingly being used in powered hand tools, gear pumps, and
as accessory components in automotive transmissions, P/M steel gears are currently in limited use invehicle
transmission applications. The primary objective of this project was to develop high strength P/M steel gears
with bending fatigue, impact, and pitting fatigue performance equivalent to current wrought steel gears.
Ausform finishing tooling and process was developed and applied to powder forged (P/F) steel gears in order
to enhance the strength and durability characteristics of P/M gears, while maintaining the substantive cost
advantage for vehicle transmission applications.
Bending fatigue and impact strength of ausform finished P/F steel gears were demonstrated to be comparable
to conventional wrought steel gears. Pitting fatigue life of ausform finished P/F gears was about 85% higher
than wrought steel gears produced by current conventional processing techniques. Scoring and wear
resistance of ausform finished P/F steel gears were also shown to be substantially superior to conventional
wrought steel gears. This paper presents the processing techniques used to produce ausform finished P/F
steel gears, and comparative bending fatigue, impact and surface durability performance characteristics of
ausform finished P/F steel gears as welll as conventional wrought steel gears.