激光冲击强化对W6Mo5Cr4V2高速钢材料表面性能的影响

Effects of Laser Shock Processing on Surface Properties of W6Mo5Cr4V2 High-Speed Steel

目的研究激光冲击强化处理对W6Mo5Cr4V2(M2)高速钢材料表面性能的影响机理,探讨激光冲击强化处理可否作为提高M2高速钢刀具使用寿命的一种手段。方法以铝箔作为表面吸收层、流水作为约束层,采用高功率钕玻璃激光冲击系统对M2高速钢试样进行激光冲击强化处理,然后用砂纸对试样表面打磨,用研磨膏抛光表面,用硝酸酒精溶液浸蚀金相试样。分别用金相显微镜和扫描电镜对被冲击试样强化层的微观组织进行观察及分析,用显微硬度计测量激光冲击前后试样表层材料的显微硬度,用X射线应力测定仪测量激光冲击后试样表面的残余应力。结果当采用的激光波长为1064 nm、激光能量为9 J、光斑直径为3 mm、脉宽<12 ns、激光功率密度为12.7 GW/cm^2时,M2高速钢材料强化层中的奥氏体晶粒显著细化,形成位错马氏体与孪晶马氏体的混合组织,M2试样表面硬度较激光冲击处理前提高约6.67%左右。试样表面获得了约1.0 mm深的残余压应力层,最大残余压应力在表层,约为-155 MPa。结论激光冲击强化处理在一定程度上改善了M2高速钢材料的表面性能,有利于提高M2高速钢刀具的切削性能与使用寿命。

The work aims to know if laser shock processing can be used to prolong the service life of M2 high-speed steel cutting tools by studying mechanism of effects of laser shock processing treatment on surface properties of W6Mo5Cr4V2（M2） high-speed steel. With aluminum foil as a surface absorbing layer and running water as a constraining layer, laser shock processing was performed to M2 high-speed steel cutters using high-power Nd glass laser shock system. Then the surfaces of specimens were grinded with sandpaper and polished with abrasive paste. The metallographic specimens were eroded with ni- tric-acid-alcohol solution. Microstructures of strengthened layer of shocked specimens were observed and analyzed with metal- lographic microscope and scanning electron microscope. Surface microhardness of specimens before and after laser shock processing was measured with hardness tester. Surface residual stress of shocked specimens was measured with X-ray stress analyzer. Provided with laser wavelength of 1064 nm, laser energy of 9 J, spot diameter of 3 mm, pulse width of less than 12 ns and laser power density of 12.7 GW/cm2, austenite grains in the strengthened layer of M2 steel were refined significantly, and mixed microstructure of dislocated martensite and twinned martensite was produced. The surface hardness after LSP increased slightly by 6.67%, compared with that before LSP. A nearly 1.0 mm deep residual compressive stress layer was obtained on the surfaces of specimens, and the maximum residual compressive stress of about -155 MPa was present in the outermost layer. To a certain degree, laser shock processing treatment improves surface properties of M2 high-speed steel, therefore contributing to the improvement of cutting performance and service life of M2 high-speed steel cutting tools.