High Cycle Fatigue Property of Carburized 20Cr Gear Steel under Axial Loading

摘要

The high cycle fatigue property of carburized 20Cr gear steel was experimentally investigated under axial loading with a stress ratio of zero. The test results show that this steel exhibits gradually decreasing S - N characteristics, and the fatigue strength corresponding to 10 9 cycles is about 455 MPa. Based on the observation of fracture surfaces, the interior inclusion fisheye-induced fracture is the predominant fracture mode in the life regime beyond 10 5 cycles. The fine granular area (FGA) cannot be found clearly around the inclusion. Based on the evaluation of stress intensity factor ranges (Δ K ) at the front of inclusion and fisheye, the interior crack growth rate (d a /d N ) equation can be characterized by d a /d N = 2.39 × 10 ?21 (Δ K ) 12.32 . Corresponding to the tested specimen, the predicted maximum inclusion size is about 52.02 μm. The predicted fatigue strength corresponding to 10 9 cycles by using Wang’s model is slightly higher than the experimental result, but that by using Murakami’s model is relatively conservative.