新型纳米贝氏体/马氏体复相超高碳高硅轴承钢滚动接触疲劳破坏机理研究

Recently, nanobainitic steels have been hot materials for long life bearings due to their excellent comprehensive mechanical properties. Bearings are key components subjected to extremely high loadings in engineering structure and transportation, and rolling contact fatigue is the main failure mode during their operation. At present, increasing the hardness, improving the stability of retained austenite and imploring the rolling contact fatigue failure mechanisms are the major issues in nanobainitic steels. This project aims to prepare a duplex structures composed of nanobainite and martensite by designing alloys with ultrahigh carbon and high silicon contents and matched heat treatments. The emphasis of this project are: ( 1 ) to study the controling factors influencing the stability of retained austenite ( 2 ) to reveal the rolling contact fatigue failure mechanism of the duplex structures under cyclic Hertzain stress ( 3 ) to establish the prediction model for rolling contact fatigue life based on continuum damage mechanics and fracture mechanics theories. This project will provide theoretical and experimental evidence for the rolling contact fatigue failure mechanism and its application as bearing materials of the nanobainite.

纳米贝氏体钢具有优异的综合机械性能，目前已成为长寿命轴承钢研究领域的热点材料。轴承是工程结构和交通运输中关键的承载部件，滚动接触疲劳破坏是其运行过程中的主要失效形式。当前，增加纳米贝氏体钢的硬度、提高残余奥氏体稳定性及探明纳米贝氏体的接触疲劳破坏机理是纳米贝氏体在轴承领域面临的难点和重点问题。本课题拟设计超高碳高硅铁合金，通过配套的热处理工艺制备高硬度的纳米贝氏体+马氏体复相组织及高稳定性薄膜状残余奥氏体。重点研究影响残余奥氏体稳定性的控制因素；揭示循环赫兹应力作用下纳米贝氏体+马氏体复相组织的接触疲劳破坏机理；基于连续介质损伤力学和断裂力学理论，构建不同特征复相组织的滚动接触疲劳寿命预测模型。本项目的旨在为纳米贝氏体滚动接触疲劳损伤机理的完善及其在轴承等领域的应用提供一定的理论和实验依据。

纳米贝氏体/马氏体复相钢具有优异的抗滚动接触疲劳性能及磨损抗力，这些特性使其在轴承领域具有重要的应用前景。本课题主要研究了该复相组织特征对滚动接触疲劳和磨损机理的影响。结果表明：（1）纳米贝氏体片层厚度并非越薄越好，而是存在一个临界尺寸，本实验中270℃等温后贝氏体厚度为81.8±27.2 nm寿命最长；（2）对于不同碳含量钢种，存在最佳的奥氏体化温度，如1.17 wt.%C钢奥氏体化温度为880℃时的疲劳寿命较长，且相同条件下奥氏体化后碳含量约0.8 wt.%疲劳寿命较长；（3）亚表面裂纹扩展时，应力集中诱发裂纹尖端附近纳米贝氏体片层形成更小的超纳晶及其边缘非晶；不同特征纳米贝氏体在形成超纳晶时需耗散的能量不同，导致不同的疲劳抗力；（4）纳米贝氏体/马氏体复相组织磨损抗力比单一组织优异。这些成果为纳米贝氏体/马氏体复相钢在轴承领域的应用提供理论支撑和实验指导。