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<p>This study investigates the fatigue strength of 51CrMnV spring steel treated by traditional quenching–tempering (Q&amp;T) and quenching–partitioning (Q&amp;P) processes, aiming to explore the feasibility of enhancing fatigue performance via retained austenite (RA) regulation. High-temperature quenching oil (HQO, flash point 370 °C) and routine quenching oil (RQO, flash point 165 °C) were used for heat treatment. Rotating bending fatigue tests, microstructural analyses (SEM, EBSD, TEM), and phase analysis (XRD) were conducted to correlate microstructural evolution with fatigue behavior. Results show that the Q&amp;P process, involving quenching in 180 °C HQO and partitioning at 350 °C, increases RA content from 2.3% (Q&amp;T) to 9.7%, with carbon content in RA rising from 0.77 to 1.36%. Nanoscale film-like retained austenite (RAf, 55–90 nm) forms at the interfaces between martensite (M) and bainite (B). The fatigue strength (σ<sub>−1</sub>) of Q&amp;P samples reaches 660 MPa, ~ 3% higher than Q&amp;T (641 MPa). Microstructural analysis reveals that Q&amp;P increases the proportion of high-angle grain boundaries (HAGBs, 81.2% vs. 75.6% in Q&amp;T), reduces kernel average misorientation (KAM, 0.58° vs. 0.75°) and geometrically necessary dislocation (GND) density (11.68 × 10<sup>14</sup>/m<sup>2</sup> vs. 15.25 × 10<sup>14</sup>/m<sup>2</sup>), effectively suppressing crack initiation and propagation. This study confirms that the Q&amp;P process optimizes RA content, distribution, and stability, synergistically regulating multiphase interfaces to enhance fatigue strength. The findings provide a new heat treatment pathway for high-performance spring steels in automotive lightweighting applications.</p>

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Effect of Quenching–Tempering and Quenching–Partitioning Processes on the Fatigue Strength of Microalloyed 51CrMnV Spring Steel

  • 期刊论文

  • 发表日期：

    2025年11月6日

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  • Rongfu Xu,
  • Shaojie Zheng,
  • Qian Yin,
  • Peng Qi,
  • Simon Yisheng Feng,
  • Yunshan Zhang

摘要

This study investigates the fatigue strength of 51CrMnV spring steel treated by traditional quenching–tempering (Q&T) and quenching–partitioning (Q&P) processes, aiming to explore the feasibility of enhancing fatigue performance via retained austenite (RA) regulation. High-temperature quenching oil (HQO, flash point 370 °C) and routine quenching oil (RQO, flash point 165 °C) were used for heat treatment. Rotating bending fatigue tests, microstructural analyses (SEM, EBSD, TEM), and phase analysis (XRD) were conducted to correlate microstructural evolution with fatigue behavior. Results show that the Q&P process, involving quenching in 180 °C HQO and partitioning at 350 °C, increases RA content from 2.3% (Q&T) to 9.7%, with carbon content in RA rising from 0.77 to 1.36%. Nanoscale film-like retained austenite (RAf, 55–90 nm) forms at the interfaces between martensite (M) and bainite (B). The fatigue strength (σ−1) of Q&P samples reaches 660 MPa, ~ 3% higher than Q&T (641 MPa). Microstructural analysis reveals that Q&P increases the proportion of high-angle grain boundaries (HAGBs, 81.2% vs. 75.6% in Q&T), reduces kernel average misorientation (KAM, 0.58° vs. 0.75°) and geometrically necessary dislocation (GND) density (11.68 × 1014/m2 vs. 15.25 × 1014/m2), effectively suppressing crack initiation and propagation. This study confirms that the Q&P process optimizes RA content, distribution, and stability, synergistically regulating multiphase interfaces to enhance fatigue strength. The findings provide a new heat treatment pathway for high-performance spring steels in automotive lightweighting applications.