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对20CrNiMo钢进行表面激光冲击强化处理,利用金相显微镜和透射电镜观察试样表面的塑性变形区域进行观察,分析了表面微观强化的过程。实验结果表明,激光冲击能够导致试样表面的硬度增加30%,残余压应力有较大程度的提高。从TEM照片可以观察到,在20CrNiMo钢表面为严重塑性变形区,此区域出现了晶粒细化,其演变过程为珠光体被打断成若干碎片,产生亚微米级亚晶结构,同时激光冲击导致材料表面整齐的纤维组织沿不同方向滑移,继而出现无定形态,最终在无定形态中出现了次级的珠光体晶粒。
The surface of the 20CrNiMo steel was laser shock-strengthened, and the plastic deformation area of the sample surface was observed by using a metallographic microscope and a transmission electron microscope. The microscopic strengthening process was analyzed. The experimental results show that laser shock can increase the hardness of the sample surface by 30% and the residual compressive stress to a greater extent. From the TEM images, it can be observed that the surface of 20CrNiMo steel is a serious plastic deformation zone, and the grain refinement appears in this region. The evolution process is that the pearlite is interrupted into several fragments, resulting in sub-micron subgrain structure with laser shock Resulting in material surface neat fiber along different directions slip, and then appear amorphous state, and ultimately in the amorphous form of secondary pearlite grains.