磨料水射流喷丸对渗碳GDL-1钢表面性能及残余应力场热松弛行为研究

采用后混合磨料水射流喷丸对经渗碳风冷后的GDL-1钢进行表面强化与改性，通过激光共聚焦显微镜，扫描电镜，透射电镜，显微硬度仪，X射线应力衍射仪分析不同压力水喷后试样表面粗糙度、组织、硬度和残余应力等的变化规律，并研究300 MPa水喷处理后不同保温温度和保温时间残余应力场的热松弛行为。结果表明：随着水压的增加，表面粗糙度增大、残留奥氏体转变量增多、硬度提高幅度变大，水喷后，晶粒和组织得到明显细化，并且在表层形成一定深度的残余压应力场。残余应力的热松弛主要受保温时间和温度的影响，在100℃和300℃时，残余应力的热松弛受回复过程控制，500℃时，残余应力热松弛受回复和再结晶过程控制。表面残余应力在回复过程中存在两个阶段，初始阶段应力松弛速度快，以点缺陷回复为主，后一阶段松弛速率慢，以位错回复为主，并进一步研究指出Zener-Wert-Avrami方程并不适合描述整个回复过程。

Study on Surface Properties and Thermal Relaxation Behavior of Residual Stress Field of Carburizing GDL-1 Steel after Abrasive Water Jet Peening

After carburizing and air-cooling, the GDL-1 steel is strengthened and modified by abrasive waterjet peening. LEXT, SEM, TEM, micro hardness tester and X-ray diffraction is used to analyze the variation of surface roughness, microstructure, hardness and residual stress etc. under different water pressure. Besides, the thermal relaxation behavior of residual stress field at different holding temperature and holding time is investigated after abrasive waterjet peening of 300 MPa pressure. The results show that with the increase of water pressure, the surface roughness, the amount of retained austenite transformation and the surface hardness is increased. After water jet peening, the microstructure and grain is greatly refined and a certain depth of residual compressive stress field is formed on the surface. The thermal relaxation of residual stress is mainly influenced by the aging time and temperature. At 100℃ and 300℃, the relaxation mechanism of residual stress is controled by the recovery process. At 500℃, the relaxation mechanism is controled by the recovery and recrystallization process. There are two stages in the process of recovery of surface residual stress, At the initial stage, the stress relaxation rate is fast and dominated by the point defect recovery. At the latter stage, the relaxation rate is slow and mainly dominated by the dislocation recovery, and the Wert-Avrami-Zener equation is not suitable to describe the whole process of recovery.