激光淬火对40CrNiMo高强度钢拉伸性能与断口形貌的影响

利用CO₂激光对40CrNiMo高强度钢表面进行了淬火处理，通过拉伸对比试验分析了激光淬火处理对试样拉伸性能的影响，用扫描电镜和能谱分析仪观察了激光淬火前后试样断口形貌与化学成分组成，并对其断裂机理进行了探讨。结果表明：激光淬火后40CrNiMo的屈服强度、抗拉强度和伸长率分别提高了25.3%、24.4%和7.1%，而断面收缩率降低了7.6%，存在明显的屈服阶段，呈现出连续屈服特征；与原始试样相比，激光淬火后40CrNiMo的屈服强度和抗拉强度明显提高，拉伸断裂方式和分层现象没有明显改善，试样表面断口处孔隙率降低，呈现准解理形貌。

Effect of Laser Quenching on Tensile Properties and Fracture Analysis of 40CrNiMo High Strength Steel

The surface of 40CrNiMo high strength steel is treated with CO₂ laser, the effect of laser quenching on tensile property of the sample is investigated through the tensile comparative test, and the fracture morphologies of 40CrNiMo before and after surface laser quenching are analyzed by scanning electron microscope and energy dispersive spectrometer, respectively. The results show that the yield strength, tensile strength and elongation of 40CrNiMo steel after laser quenching are increased by 25.3%, 24.4% and 7.1%, respectively, while the section shrinkage is decreased by 7.6%. 40CrNiMo steel has obvious yield stage after laser quenching, showing a continuous yield feature. Compared with the primitive sample, the yield strength and tensile strength of 40CrNiMo steel after laser quenching increase, but there are no obvious improvements in the tensile failure mode and the delamination, and the quasi cleavage morphology and low porosity appear at the fracture near the surface of the sample after laser quenching.