Fatigue Strength and Dynamic Performance of Induction-Hardened Sintered Powder Metal Gears. Comparison with Steel Gear and Influence of Hardened Depth.

Abstract

Int this paper, induction-hardened sintered powder metal spur gears were compared with an induction-hardened melted steel spur gear in terms of fatigue strength and dynamic performance, and the influence of hardened depth on the fatigue strength of the sintered gears was also investigated, using a power circulating gear testing machine. The damping characteristic of the sintered gear was superior to that of the steel gear, but the fatigue strength of the sintered gears was inferior to that of the steel gear, since many pores existed in the sintered gears. The failure mode of the sintered gears was pitting with spalling, and that of the steel gear was tooth breakage due to pitting. We consider the origin of pitting of the sintered gears was pores, while the origin of the pitting of the steel gear was defects on the tooth surface. The fatigue strength and the failure mode of the sintered gears were not influenced by hardened depth. During the fatigue processes of both the sintered gears and the steel gear, the changes in dynamic performance were almost the same since the tooth surface deteriorations of both types of gears were similar in shape. Both dynamic performances became worse due to the tooth surface deterioration.