激光功率对40CrNiMoA钢表面淬火组织和摩擦磨损性能的影响

采用不同激光功率在卷取机卷筒主轴40CrNiMoA钢基材表面进行了激光淬火试验,利用体视显微镜、光学显微镜、显微硬度计和立式万能摩擦磨损试验机等观察和测试试样横截面的宏观组织、表面显微组织、激光相变硬化区的显微硬度和摩擦磨损性能。结果表明:3种不同功率下的激光淬火试样表层组织均得到不同程度的细化,其硬度、摩擦磨损性能较基体均有所提升。其中,当功率为1600 W时,在试样截面能够明显观察到相变硬化区。此时,试样的表层组织最为细致,由细小的针状马氏体、少量残留奥氏体和弥散分布的细小碳化物组成,其表面硬度可达640.3~706.8 HV0.2,约为基体硬度的2.8倍。同时,摩擦因数稳定在0.40~0.60之间,与基体相比降低了50%左右;磨损量1.3 mg,仅为基体的36.1%。在光斑尺寸12 mm×2 mm,扫描速度v=20 mm/s的试验条件下,采用1600 W激光功率对40CrNiMoA钢进行表面激光淬火,得到的试样组织和摩擦磨损性能最优。

Effect of laser power on quenched microstructure and friction and wear properties of 40CrNiMoA steel

The surface layer of the coiled spindle main shaft 40CrNiMoA steel base material was tested by laser-quenching with different power. The macroscopic structure of cross-section, surface microstructure, microhardness, and friction and wear properties of the specimens were observed or tested by means of stereo microscope, optical microscope, microhardness tester, vertical universal friction and wear tester. The results show that, the surface structure of the laser hardened specimens at different powers exhibit different levels of refining, and compared with the matrix, the hardness and friction and wear properties are improved. When the power is 1600 W, the laser hardened layer can be clearly observed in the cross-section of the specimens, and the surface layer of the specimens is the most detailed, consisting of fine acicular martensite, a small amount of retained austenite and a finely distributed fine carbide, and the surface hardness can reach 640.3-706.8 HV0.2, which is about 2.8 times of that of the substrate. At the same time, the friction coefficient is stable between 0.40 and 0.60, which is about 50% lower than that of the substrate. The amount of wear is 1.3 mg, which is only 36.1% of the substrate. Under the test conditions of spot size with 12 mm×2 mm, scanning speed with 20 mm/s and laser power with 1600 W, the obtained microstructure and friction and wear properties are optimized after surface laser quenching of 40CrNiMoA steel.