Tooth root bending fatigue strength of small-module sinter-hardened spur gears

The present paper is aimed at investigating the effect of the sinter-hardening treatment in improving the tooth root fatigue resistance of gears obtained by Powder Metallurgy. The gears were produced using two types of low-alloyed partially diffused steel powders, Distaloy DC and Distaloy DH (Höganäs AB, Sweden), that were conventionally sintered as well as sinter-hardened. A different microstructure was obtained after the two sintering processes that led to different fatigue response. As expected, the martensitic microstructure is responsible for good fatigue performances, slightly less than those of gears made with wrought low-alloyed quenched and tempered steels.