ORIGINAL RESEARCH article
Front. Mater.
Sec. Structural Materials
This article is part of the Research TopicMechanical Behavior and Dynamic Response of Materials and Structures Under Complex Loads and WavesView all articles
Effect of heat treatment on very-high-cycle fatigue performance of EA4T axle steel
Provisionally accepted
- 1Harbin University, Harbin, China
- 2Xinjiang Cigarette Factory, Hongyun Honghe Tobacco (Group) Co., Ltd., Urumqi, China
- 3重庆工程学院, 重庆市, China
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The fatigue performance of EA4T (25CrMo4) axle steel was investigated using small-specimen rotating-bending tests up to 2 × 10⁸ cycles to clarify how heat treatment affected high-cycle and very-high-cycle fatigue (HCF/VHCF) behavior. Five specimen groups, four heat-treated and one as-received, exhibited microstructures from tempered martensite to sorbite and pearlite + ferrite. As tempering temperature increased, tensile strength declined from 1029 MPa to 752 MPa, with corresponding fatigue limits decreasing from 470 MPa to 295 MPa. Staircase-based analysis yielded lower-bound strengths of 336 MPa (10% failure) and 319 MPa (1%, 95% confidence). SEM fractography confirmed surface crack initiation in all cases, indicating the absence of internal VHCF origins. A consistent correlation between hardness and fatigue strength revealed a clear strength– durability trade-off across microstructures. These results establish quantitative links between tempering, hardness, and fatigue resistance, providing practical guidance for optimizing heat-treatment windows and microstructures to enhance the reliability and safety of high-speed train axles.
Keywords: EA4T steel, Fatigue limit, Heat treatment, High-speed train axle, Staircase method, Very-high-cycle fatigue (VHCF)
Received: 03 Dec 2025; Accepted: 14 Jan 2026.
Copyright: © 2026 GAO, QIU, ZHANG and LIU. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Shisen LIU
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