P/M GEAR FOR A PASSENGER CAR GEAR BOX (1,21MB)

Powder Metallurgy (P/M) gears with residual porosity have lower strength and wear resistance when compared to wrought and machined gears and hence have not been employed in heavy-duty applications. Substantial improvements in strength and wear resistance of P/M gears are achieved by selective surface densification through transverse rolling. This paper deals with the manufacturing of a helical P/M gear for a passenger car gear box by compaction, sintering, selective surface densification, case hardening and possibly final honing depending on the required quality level. The influence of various parameters such as material composition, transverse rolling and heat treatment process parameters on the densification and hardness depth, pore morphology, microstructure, gear geometry, DIN-quality and surface roughness have been studied. Preliminary investigations have been carried out on a 3-shaft back to back test rig which indicate that the P/M gears have a high load bearing capacity.