Surface Densified P/M Gears Made of Chromium Alloy Powder Reach Automotive Quality
A final-drive idle helical gear from a passenger car transmission was made of water atomized and fully pre-alloyed Fe-1.5Cr-0.2Mo powder. The gear samples were cold compacted to 7.1 g/cm³, sintered, surface densified by radial gear rolling and casehardened. A 3D gear meas-urement center was used to evaluate profile, alignment, pitch and runout deviations of the gears after the gear rolling and after the casehardening. The gears achieved an overall DIN 7 quality after rolling for all single deviations suggested in DIN 3961 to have general or particu-lar importance for uniformity of rotation, load capacity and noise reduction of gear. After the low-pressure casehardening, the overall gear quality for the deviations as above was DIN 7, except for the total profile deviation Fá, which achieved DIN 10 quality. To achieve DIN 7 gear quality after casehardening, further work should include activities on reduction of the tooth width contraction along the tooth height.