Fatigue properties and influencing factors of carburized gear steel 18CrNiMo7-6

doi:10.13251/j.issn.0254-6051.2023.01.011

Abstract

Abstract: Taking 18CrNiMo7-6 gear steel as base steel, a tested 18CrNiMo7-6 gear steel was prepared by traditional vacuum degassing smelting + Nb microalloying + electroslag remelting smelting, then the fatigue properties and influencing factors of both steels were comparatively studied by rotary bending fatigue test combined with analyses and characterization of microstructure, hardness distribution, inclusions and fatigue fracture. The results show that the fatigue limit of the tested steel smelted by electroslag remelting and Nb microalloyed is 90 MPa higher than that of the base steel, the service life under the same load is significantly increased, the grain size of the carburized layer of the tested steel is refined from grade 7.5 of the base steel to grade 9, but the surface hardness is decreased due to the increase of retained austenite content. The Aspex inclusion characterization shows that the number of inclusions in the tested steel is significantly lower than that in the base steel, and there are fewer hard oxide inclusions, which is consistent with the fracture characterization results. The comprehensive analysis shows that the grain refinement and decrease of non-metallic inclusion level are the main influencing factors to improve the fatigue properties of the tested steel.

Key words: 18CrNiMo7-6 carburized gear steel, grain size, non-metallic inclusion, fatigue properties

CLC Number:

TG142.1⁺3

Zhang Xiaolu, Hai Xianü, Gui Weimin, Yu Wenchao, Shi Jie, Wang Maoqiu. Fatigue properties and influencing factors of carburized gear steel 18CrNiMo7-6[J]. Heat Treatment of Metals, 2023, 48(1): 60-67.

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