Application Requirements and Material Selection of Surface Densified P/M Gears for Automotive Gearboxes
The high dimensional and mechanical requirements have in the past limited or prohibited the use of gears produced by powder metallurgy for automotive transmissions. The introduction of a technique for selectively densifying the highly loaded regions of the gear provides a production route for high performance gears. The present work is part of a larger program that aims at demonstrating the feasibility, quality and economics of producing surface densified P/M gears for automotive gearboxes. The selected gear is the 5th gear (fixed) from a line of gearboxes for Renault passenger cars. It is characterised by a helical angle of 30°, it has 31 teeth and internal splines. In order to select a material a series of surface densified rollers were manufactured and tested for rolling contact fatigue strength. The results show that the Distaloy DC1 can match the solid steel reference material. The investigations were carried out as part of a project funded by the European Commission under the “Competitive and Sustainable Growth” program (Project No: GRD1-1999-10674).