激光冲击修复后压力容器钢Q345R耐腐蚀及抗疲劳性能研究

对激光冲击强化后的压力容器材料Q345R钢的耐腐蚀性能和抗疲劳性能进行研究。通过电化学实验，并结合扫描电子显微镜分析其耐腐蚀性。结果显示，有吸收层保护和无吸收层保护激光冲击后，相较于原试样，耐腐蚀性分别提升5.8倍和2.6倍；微观实验结果表明经过激光冲击后腐蚀试样表面裂纹明显少于未处理试样。但随着冲击次数增加,耐腐蚀性有所下降。疲劳试验结果显示，相同应力条件下，腐蚀1和2 h的疲劳寿命相较于原试样降低36.8%和56.4%，经过一次或三次激光冲击后试件的疲劳寿命分别提升43.8%和198.2%，经XRD检测,激光冲击能在表面形成一定深度的残余压应力层并抑制裂纹扩展。

On corrosion and fatigue resistance of pressure vessel steel Q345R after laser shock repair

Electrochemical corrosion and fatigue tests were carried out to study the corrosion resistance and fatigue resistance of the pressure vessel material Q345R steel after laser shock peening (LSP). The material was cut into samples of 6 mm×10 mm×10 mm, with water as constraint layer and black tape as absorption layer. Laser shock peening was carried out for 1, 3, 5 and 7 times respectively. The samples were immerged in 3.5% NaCl solution for electrochemical corrosion. Tafel extrapolation method was used to obtain the polarization curves of the corrosion resistance of the reactive materials. The results show that the samples have the best corrosion resistance after a single shock, their corrosion resistances decrease after multiple shocks, the corrosion resistance without black tape decreases more obviously, the black tape serving as absorbing layer can effectively protect the sample from the LSP damage. The micro-observations show that surface cracks on corrosion specimen after LSP were significantly less than those on the untreated sample. S-N curves were obtained by MTS fatigue test of samples after different corrosion time and LSP times. The results show that under the same stress condition, the fatigue life of samples after 1- or 2-hours’ corrosion decreased 36.8% and 56.4%, respectively compared with that of the original sample. After one and three shocks, the fatigue life of the specimens increases 43.8% and 198.2%, respectively. X-ray diffraction (XRD) was used to analyze the residual stress on the surface of the sample. It was detected that the residual tensile stress on the surface of the untreated sample is 34.4MPa, and the residual compressive stresses on the surface of samples after one and three shocks were 205.6 and 288.5 MPa, respecitvely. It indicates that the residual compressive stress layer with a certain depth was formed on the surface, which inhibited the crack propagation and improved the fatigue life.