40Cr钢表面激光复合强化机理研究

利用NEL2500A轴向快速流动CO3激光器对40Cr钢进行了激光淬火处理，又利用Nd：YAG激光器对40Cr钢的淬火马氏体强化区进行了激光冲击强化处理，选用K9玻璃为约束层。处理结果表明，40Cr钢的复合强化处理区与激光淬火强化处理区相比，马氏体区表面发生了超塑性形变，马氏体发生了细化和碎化，位错密度大大增高，各项机械性能都得到了大幅提高，其中，硬度提高了10．9％，耐磨性提高了100%，尤其是材料内部残余应力全部变成了残余压应力，表面最大残余应力达到-372MPa。

Study on Experiments and Mechanism of 40Cr Steel Surface by Laser Compound Processing

40Cr steel was quenched by the NEL-2500A rapidly axial flow CO2 laser. The optimized experimental parameters were that the laser power was 750 W, the diameter of laser beam was 4 mm and the scanning velocity was 7 mm/s. The thickness of coating layer was 0.1 mm and the width was 8 mm. Moreover, the martensite induced by laser quench was shocked by Nd∶YAG laser again. The parameters of laser shock processing were the wavelength of 1.06 μm, the pulse duration of 23 ns and the output power of 16～20 J. The laser was focused on a spot of 7 mm. K9 optical glass was used as confinement. The sample was coated with black paint 86-1 (the thickness was about 0.025 mm). By test and analysis of properties and transmission electron microscope (TEM) micrographs of samples which were treated by laser quench and laser quench+shock, the results indicate that the martensites obtained through laser compound treatment have become more finer than those obtained in laser quenching. In the hardened zones obtained through compound method, a lot of slender secondary twin crystal martensites have been produced. In the hardened zones, there generate large number of dislocation tangles and produce many cellular dislocations; the properties of the zone treated through compound methods are improved, compared to that through only laser quenched. The hardness increases by 10.9% and the wear-resistance enhances 100%. Especially, the residual stress of the interior of the material was changed into compressive stress and the max-residual stress of surface reached -372 MPa.