Evaluating The Rolling Contact Fatigue Properties Of Surface Densified PM Gears

Surface densification technology allows powdered metal (PM) manufacturing methods to be considered for use in highly stressed product groups such as automotive transmission gears. The paper shows that rolling contact fatigue performance is defined by the interaction of the applied subsurface shear stress profile and the material shear fatigue strength profile.

Previous work has shown that surface densified PM gears can provide rolling contact fatigue durability which is at least equivalent to that of wrought steel gears. In respect to the provision of appropriate rolling contact fatigue design data, it is shown that cylinder based test parameters need to be diligently selected, reference in particular needs to be made to actual automotive transmission gear geometrical features, and to the microstructure of the proposed material.

It is shown that in the application of cylinder test data to actual components, the maximum surface compressive stress, the peak shear stress and the depth of the shear stress profile, need to be considered as design criteria.