摘要
以45#钢为研究对象,采用波长1064 nm的脉冲激光在45#钢表面进行微凸起造型,利用扫描电子显微镜和三维形貌仪表征形貌。试验得到球冠状、墨西哥帽状和M状形貌三种典型微凸起形貌。结合温度场以及气化反冲压力数值估算,系统研究了激光脉宽和峰值功率密度对微凸起形貌的影响规律,提出了一种火山口形貌形成的新机理。结果表明:微凸起形貌是激光与材料作用过程中热、力耦合作用的结果。中心凸起形貌由熔池内对流形成,峰值功率密度低,脉宽短,形成球冠状形貌。峰值功率密度越高、脉宽越大,所得中心凸台越高越细,演变为墨西哥帽状。当熔池中心温度超过材料沸点,材料气化形成的反冲压力,在熔池中心凸起顶端反压出凹陷,形成M状形貌。该结论有助于控制脉冲激光毛化制造微凸起的微观形貌。
Pulse-width laser is used to manufacture micro-convex points on the surface of 45# steel. Scanning electron microscopy and three dimensional （3D） profiler are used for measuring the morphologies of the micro- convex points. Three typical morphologies （spherical-cap shape, Mexican-sombrero shape, and M-type donut shape） are observed in experiments. Conducted the numerical estimations of the temperature field and gasification recoil pressure, and the influences of pulse width and peak power density on the morphology have been researched systematically through the experimental and theoretical analysis, a new formation mechanism of the crater shape is proposed. The formation of the micro-convex points is the result of the coupling of heat and force. Under the effect of the temperature gradient, the liquid metal in the molten pool flow from the edge to the center, which produces micro-convex finally. Spherical-cap shape tends to be formed when peak power density is small and pulse width is short. With the increase of the pulse width and peak power density, the diameter of the central convex point become smaller and its height increases. Micro-convex points evolve into Mexican-sombrero shape. When the temperature at the central of the molten pool exceeds the gasification temperature, gasified materials can form recoil pressure exerting on the molten pool, which presses down the top of the convex. Thus, M-type donut shape is formed. The results are beneficial for controlling the morphologies of the micro-convex points during laser surface texturing.
出处
《激光与光电子学进展》
CSCD
北大核心
2016年第3期148-157,共10页
Laser & Optoelectronics Progress
基金
国家自然科学基金(51205172)
机械系统与振动国家重点试验室开放课题基金
关键词
激光技术
激光微造型
工艺试验
对流
温度场
反冲压力
laser technique
surface texturing
process experiment
convection
temperature field
recoil pressure
