Evolution of Gear Quality in Helical PM Gears During Processing
A helical PM gear for a passenger car gear box was manufactured by pressing, sintering and selective surface densification using transverse rolling. The evolution of gear properties in terms of microstructure, geometry, surface roughness and DIN-quality is monitored at each step of the processing sequence. The geometry of the PM gear is compared to a conventional wrought steel gear being currently used in the gear box. It is shown that PM gears can be manufactured well within the DIN “quality 8” tolerance fields. Furthermore it is demonstrated that alignment and profile errors can be reduced in the sequence of processing. While wrought gears have less alignment and profile errors, PM gears are superior in terms of run-out and pitch errors as well as surface roughness. These investigations were carried out as a part of a project funded by the European Community under the “Competitive and Sustainable Growth” Program (Project No.: GRD1-1999-10674).