Pitting resistance of sintered small-module gears

Sintered small-module gears have two important aspects that readily follow from the name: they are sintered and with a small module of 1.5875mm (DP 16). Both aspects are to date insufficiently described for gear designers despite an increased need for sintered small-module gears. This article reviews a decade of systematic experimental investigations with regard to pitting resistance of sintered small-module gears. Pitting resistance levels are listed for the common pressing/sintering/surface densification technologies of today. Currently the highest pitting resistance of 1300MPa is achieved for pressed, sintered, rolled, re-sintered and case carburized low-alloy gears in comparison with 1800MPa for the reference ground case-carburized 16MnCr5-wrought gears. This offset can, however, be compensated by selection of a relatively higher viscosity and lower operating temperature of the lubricating oil, if the application allows it. Thus, powder metal technology can once again contribute to a competitive total cost with high material utilization.