Surface Densification of Helical and Spur Gears
The past decades have seen a continuous growth of the use of PM parts in automotive applications. However, the performance requirements the components must meet are more and more demanding. Transmission gears for automotive applications are complex in shape and require very high geometrical accuracy in terms of gear quality (DIN, ISO, AGMA, etc) and also very high mechanical performance in terms of durability of tooth flank and root. Powder metallurgy is very cost effective for complex shaped parts and by adding a selective densification of the teeth the accuracy and mechanical performance requirements can be met at a very low added cost. A process route consisting of compaction, sintering, surface densification by rolling and finally heat treatment was used to assess the feasibility of producing transmission gears by powder metallurgy. Helical and spur gears were used in the study where the densification as well as the resulting gear quality and tooth root fatigue was tested.