Opportunities for High Performance PM Gears in Automotive Applications
The past decades have seen a continuous growth of use of PM parts in automotive applications. However, the performance requirements future components must fulfill are becoming more and more demanding. Transmission gears for automotive applications are complex in shape and require both very high geometrical accuracy in terms of gear quality and very high mechanical performance in terms of durability of tooth flank and root. PM offers possibilities to produce complex shaped parts in a very cost effective way and by adding a selective densification of the gear teeth both accuracy and mechanical performance requirements can be met at a low added cost. In this paper a process route consisting of compaction, sintering, surface densification by rolling and finally heat treatment have been studied to assess the feasibility of producing high performance gears for automotive applications by powder metallurgy. Helical and spur gears were used in the study where the densification as well as the resulting gear quality and durability were tested.