Fabrication
All five components are made of pre-alloyed low-alloy steel (PF-4620 and PF-4620 modified for the locking plate), produced to a minimum density of 7.80 g/cm3, and delivered in the carburized, quenched, and tempered condition with a surface hardness of 58–62 HRC. The case profile and core hardness is unique for each component. Net-shape forging yields the external cam teeth on the locking plate, side gears with AGMA Class 6 internal splines, pinions with AGMA Class 7 bevel gear teeth, and dog teeth on both locking parts that are held to a 0.2 mm profile tolerance. Minimal machining operations are performed on thrust bearing surfaces, internal bore on the pinions, end faces on the locking plate, and chamfers on the pinion and side gears.
Results
The higher performance delivered by the powder forged differential gears compared with that of competing metal-forming processes will help usher in downsized gear systems, satisfying a critical need in future automotive design.