Influence of large carbides on rotating bending fatigue of GCr4Mo4V steel

doi:10.13251/j.issn.0254-6051.2023.02.008

Abstract

Abstract: Annealed hot rolled high temperature bearing steel GCr4Mo4V manufactured by “VIM+ESR” was heated at 1120 ℃ for 30 min before being oil quenched, and then the specimen was tempered at 530 ℃ for 2 h followed with air cooling for 3 times. The rotating bending fatigue experiment was carried out on the heat treated specimen under stress levels of 960, 1000, 1040 and 1080 MPa, respectively. The S-N curve was obtained via the experimental data. A median fatigue limit of 686 MPa is calculated accordingly. Analysis of the fracture morphology indicates that the rotating bending fracture of GCr4Mo4V bearing steel consists of 3 typical zones, which are near surface crack-initiated site, crack propagation zone and stress tearing zone. The distance between the crack initiated site and specimen surface is about 240 μm, and at the center of the crack-initiated site exists large size carbide, the particle size of which distributes in the range of 16.93-53.94 μm. The crack nucleates at the boundary between large size carbide and the matrix, and gradually propagates towards the center of the specimen; in the end, the specimen is teared into two pieces by the torsion stress. The mathematical analysis shows that, the size of the large carbides D shows a perfect linear relation with the logarithm of fatigue life N, and the mathematical relation is lg(N)=-0.053 77D+7.326 82 according to the fitting results. And it is clear that the extreme refinement of the large carbides is absolutely a significant way for life prolonging of GCr4Mo4V bearing steels.

Key words: high temperature bearing steel, rotating bending fatigue, large carbides, fatigue limit

CLC Number:

TG142.1

Cui Yi, Zhang Caidong, Yu Feng, Zhang Yunfei, Zhang Zhiwang, Cao Wenquan, Zhao Yingli, Cui Shaopu. Influence of large carbides on rotating bending fatigue of GCr4Mo4V steel[J]. Heat Treatment of Metals, 2023, 48(2): 50-55.

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