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

Abstract

Abstract: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 (∆K) at the front of inclusion and fisheye, the interior crack growth rate (da/dN) equation can be characterized by da/dN = 2.39 × 10 −21 (∆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.

Comparison of the Internal Fatigue Crack Initiation and Propagation Behavior of a Quenched and Tempered Steel with and without a Thermomechanical Treatment

“…Consequently, the lifetime period spent in the crack propagation stage should be longer when the critical inclusion is located at a larger distance from the surface. Since the results indicate no obvious influence of inclusion depth which is in good agreement with other investigations in the HCF regime [24,25], we can infer that the lifetime is mostly governed by the period before crack initiation and the crack propagation stage occupies only a small percentage of the total lifetime. We assume that this is true for both HT and TMT specimens.…”

“…However, these investigations are mostly simulation-based [15,23]. There are experimental investigations reporting no correlation between the areas of critical non-metallic inclusions or inclusion depth and lifetime (N f ) [9,24,25]. However, other studies showed that the area and inclusion depth of critical inclusions decreases with increasing lifetime [18,26].…”

Effect of variable amplitude on fatigue life of 17CrNi steel beyond 107 cycles

“…Compared to the S-N curves of the same steel under the CA loading (denoted by interrupted lines in Figure 3 [23-25]), the fatigue strength of the carburised 17Cr2Ni2Mo steel under the VA loading is a bit higher. The main reason is related to the existence of only one stress level in the CA loading however there are several stress levels in VA loading with a medium stress that is generally lower than that of CA loading (Table 2(a) and (b)).…”

Long-Life Fatigue of Carburized 12Cr2Ni Alloy Steel: Evaluation of Failure Characteristic and Prediction of Fatigue Strength

“…Due to the higher demand for reliability and safety of mechanical components in industrial design, the fatigue characteristics of structural materials has received increasingly more attention from researchers working on the field of long-life fatigue [1,2]. High carbon [3], Ti-6Al-4V [4], and high-strength alloy steel [5] have been shown to transition between surface failure in short-life region and interior failure in long life region and form typical double S-N curves.…”

“…The three stages of the FGA formation process are as follows [15]: (1) grain refinement, (2) coalescence of microcracks, and (3) FGA formation. Over the years, researchers have attempted to explain the FGA formation process in different ways, such as depressive decohesion of spherical carbide [16], hydrogen embrittlement-assisted cracking [17], cyclic compression between crack faces [18], numerous cyclic pressing [19,20], grain refinement and local stress threshold decreasing [21], and nanograin refinement at negative stress effect [2]. The varied theories on the formation of the FGA means the topic needs further study and discussion.…”