切削过程中高强合金钢浅表层性态强化研究

切削浅表层显微结构状态对机械构件力学性能和服役寿命有重要影响。为获得性能优良的切削表层，综合应用理论计算和测试分析的研究手段，对不同切削速度下高强合金钢浅表层微观结构演变和力学性能强化的内在关联展开研究。结果表明：中高切削速度能够相对最大程度实现高强钢切削表层梯度微观结构的形成，由表及里分别为致密纳米等轴晶所在的回复层，高密度亚结构聚集的流变层和晶粒残留畸变状态的畸变层。中高切速下平均晶粒尺寸相对最小（392.1 nm），同时位错密度相对最高（1.072 5×10¹² cm^-2），变形应变、位错和小角度晶界等亚结构均高度集中于流变层。经性能测试发现，中高切速实现了高强合金钢切削浅表层硬度、表面质量和韧性的同时提升，这是上述中高切速带来的微观结构变化所形成的细晶强化和位错强化综合作用的结果。

Behavior Strengthening of Superficial Layer of High Strength Alloy Steel in Machining Process

Microstructures of the cutting superficial layer has an important influence on the service performance of mechanical components. To obtain machined surfaces with excellent performance, theoretical calculation and test analysis were carried out to investigate the internal correlation between microstructure evolution and mechanical property enhancement of superficial layers of high-strength alloy steel (HSAS) under different cutting velocities. Results showed that the medium-high cutting velocity can achieve the formation of gradient microstructures of machined surfaces of HSAS maximally. From the outside to the inside, they are respectively the recovery layer where dense nano equiaxed crystals are located, and the rheological layer with high-density substructure and the distorted layer where grains are in the residual distortion. The average grain size is relatively smallest (392.1 nm) at medium-high speeds, and the dislocation density is relatively highest (1.072 5×10¹² cm^-2). Substructures such as deformation strain, dislocations and small-angle grain boundaries are highly concentrated in the rheological layer. Based on performance test experiments, it was also found that The medium-high cutting speed achieves the simultaneous improvement of the hardness, surface quality and toughness of the superficial layer of HSAS, which is the result of the combined effect of the fine grain strengthening and the dislocation strengthening formed by the microstructure changes above brought about by medium-high cutting velocity.